The result of the study in Table 2 revealed that in operating sensor technology, the farmer needed the techniques that could enable him calculate vegetation index , drive ground-based mounted device, issue appropriate command to remote sensor, manipulate the Graphical User Interface of the sensor,monitor the crop yield, interpret data and make suggestions among others. The findings of the study were in conformity with the findings of that there is need to generate maps of the soil with its characteristics which included grid soil sampling , yield monitoring, and crop scouting. The author further found out that strategically positioned sensors collect data in the form of electronic computer databases which gives birth to the Geographic Information System for statistical analyses of data and determines variability of agricultural land with respect to its properties.

The findings of the study were also in line with the findings of that an effective method used to easily interpret remote sensing data is calculating vegetation indices.Shifting cultivation or slash-and-burn agriculture is a global agricultural practice that affects an estimated arable land area of 1500 million ha . It is the traditional method of upland rice cultivation in most parts of West Africa and in the humid and sub-humid tropics. This is a practice where a piece of forest is cleared and burnt for cultivation for a period of two to three years without fertilizer input and then leaving the land under natural fallow vegetation for a much longer period, usually greater than fifteen years, to restore soil fertility .At the onset of the cropping phase, when vegetation is burnt, almost all biomass carbon which is a potential source of soil organic carbon is lost as well as a significant amount of nutrients such as nitrogen and sulphur contained in the biomass.

During the cropping phase, inappropriate soil management practices could lead to accelerated depletion of soil organic matter and nutrients resulting in rapid depletion of soil fertility.During the fallow, the accumulation of biomass on the soil surface and its gradual decomposition does not only release nutrients but provide an energy source for the soil microbial populations and improvement of soil aggregate stability and structure, bulk density, infiltration capacity, cation exchange capacity, and soil organic matter. Also,nutrients are taken up from deeper layers by roots of trees and shrubs and returned to the top soil via litter fall and root senescence.Restoration of soil fertility by this means requires several years of fallow and has become inadequate in the face of increasing populations and food demand as well as competing alternative land uses. This has led to considerable reduction in the fallow period and the cultivation of marginal lands.In Sierra Leone, the uplands account for about 80% of the total arable land.

The bush fallow system is a very common farming practice on the uplands of Sierra Leone although it is also practiced in almost all agroeclogies. Upland rice farming system involves inter cropping rice with a variety of other crops such as cassava, maize, sorghum,sesame, pigeon pea, okra, garden egg, and other leafy vegetables. Rice normally occupies about 50% of the cropland. The limitation of this system as a sustainable farming practice is the increasing decline in the fallow period. Generally, the length of fallow period is reported to differ across the country with a mean of 8.8 years . In recent times, it is reported that the fallow period has dropped from the recommended period of ten or more years to about 5 years in rural areas and 3 – 4 years along major highways .Apart from the FAO/UNDP survey in 1979 which estimated an average fallow period of 8.8, there has been very little work done to update information on length of fallow period in different parts of the country. There is lack of information on the current extent of reduction in fallow period in different parts of the country particularly in the eastern region of Sierra Leone which is home to the remaining rainforest of the country.

The continued decline in the fallow period is a major threat to the persistence of the rain forest in the eastern region of Sierra Leone as farmers are tempted to slash-and burn the remaining forest for upland rice farming. An understanding of the extent of reduction in fallow period in the Eastern Region of Sierra Leone will throw light on the magnitude of the problem and inform policy makers and land use planners to enable them develop intervention strategies to counteract the negative impact of the practice.This study was therefore conducted to determine: 1) the extent of reduction of the fallow period in the Nongowa Chiefdom of Kenema District; 2) the causes of reduction in the fallow period; 3) farmers’ perception of the relevance of fallow period and the implications of reduction of fallow period on crop production. Sierra Leone is divided into four administrative blocks: the Provinces, the Districts, the Chiefdoms, and the Sections in decreasing sizes and administrative authority respectively.

High oil germplasm was used to increase germination, as well as to assist in increasing expression 20-fold in five generations through breeding and selection. It was hypothesized that the high oillines might provide substrate for the laccase-generated free radicals to act upon, thereby preventing the accumulation of free radicals that alter seed physiology, such as increased lignification. Down regulation of onebof the major enzymes involved in lignin biosynthesis, 4-coumarate: coenzyme A ligase  in transgenicaspen , resulted in a 45% decrease in lignin with a compensation of 15% increase in cellulose,doubling the plant cellulose:lignin ratio without any change in lignin composition and without any apparent harm to plant growth, development or structural integrity . Poplar with CAD antisense constructs grows similar to control trees but with an increase in the proportion of free phenolic groups in lignin facilitating solubilization and fragmentation .

Poly 3-hydroxyalkanoates  are a class of microbially produced polyesters comprising of at least 100 different PHA constituents and at least five different dedicated PHA biosynthetic pathways  with potential application as biodegradable plastics. Arai et al.  was able to transfer from Aeromonas caviae FA440 modified PHA synthase gene  into Arabidopsis thaliana that enabled the plant to accumulate PHA in its tissues. Cahoon et al.  reported that expression of a gene from pot marigold encoding an enzyme that introduces conjugated double bonds into polyunsaturated fatty acids resulted in the accumulation of calendic acid, a novel conjugated polyunsaturated fatty acid, to amounts of 20% – 25% of the reported total soybean seed oil. Calendicacid is even more oxidatively unstable than linolenic acid, thus improving the drying properties of coating applications.However, the level of calendic acid concentration in soybean at 20% – 25% remains much lower than55% concentration found in the marigold. Castor  oil contains high levels  of ricinoleic acid needed for conversion to substitutes for petroleum derived lubricants, emulsifiers, inks, and nylons.

Unfortunately, castor cultivation is prohibited in most countries as the seeds also contain toxin ricin. The level of ricinoleic acid achieved in tobacco and Arabidopsis have been only to the amount of ˂1% and 17%, respectively. Singh et al. observed that although a single gene may regulate ricinoleic acid synthesis, its accumulation intriglycerol most likely required involvement of other genes. Napier  noted that, thus far, it has been difficult to attain levels of industrially desirable fatty acids in transgenic plants similar to found in the non-agronomic source plants.McKeon  reported the ongoing efforts to enhance industrial chemical constituents in important crops.Canola with high laurate for detergent and soybean with high oleate for food and monomers have reached commercial stage, while canola with petroselenate for food and monomers, soybean with vernolate for plasticizers and coatings, cotton with low-saturates for food uses are in development. There are many reports of transgenic plants exhibiting tolerance to varying levels of heavy metals, a trait useful for phytoremediation of contaminated soils. Arabidopsis thaliana transformed by type 2 MT gene from cattail  exhibited an increased tolerance to Cu2+ and Cd2+ .Indian mustard  plants overexpressing ATP sulphurylase were shown to have higher shoot Seconcentrations and enhanced Se tolerance compared to wild type when grown in the presence of selenite .

Family of sulfur rich peptides termed phytochelatins  are able to bind to Cd and some other heavy metals  and transgenic tobacco plants over expressing cysteine synthase in either the cytosol or chloroplasts were more tolerant to metals such as Cd, Se and Ni . Transgenic plants have been developed with altered transporter genes with the aim to exclude a toxic metal ion, transporting the metal into the apoplastic space and vacuole where metal would be less likely to exert a toxic effect. Phytoremediation uses different plant processes and mechanisms normally involved in the accumulation, complexation, volatilization, and degradation of organic and inorganic pollutants . Table 2 shows categorization of different processes used by some of the model transgenic plants in phytoremediation. Most of the information available today is either from laboratory and or greenhouse experiments. Elaborated field testing is required to validate and establish the effectiveness of these transgenic plants for actual cleanup of contaminated metal sites. Genetic transformation studies have shown the potential of producing recombinant proteins, including pharmaceuticals and industrial proteins, and other secondary metabolites in plants. Several substances have already been produced in transgenic plants and are in different stages of clinical trials  but none of them were approved as pharmaceutical for humans until 2012. Recently, an enzyme, for treating the rare hereditary Gaucher disease  generated in carrot tissue became the first Plant Made Pharmaceutical for human use to gain regulatory approval by the US FDA .

Dispersed settlement in rural Ethiopia coupled poor infrastructure including roads, transportation and telecommunication is one of the reasons for the low efficiency of AI service. Efficient delivery of AI service to individual farmers as and when each cow shows oestrous signs is impracticable. The AI service and delivery of improved dairy genetics to smallholders could be improved by introducing hormonal oestrus synchronization and mass artificial insemination . The effort to improve the dairy cattle crossbreeding/AI program through hormonaloestrus synchronization has been below expectation due to factors related to inefficient AI service, poor infrastructure and farmers’ awareness, although the synchronization technology has been successfully demonstrated through action research .An important characteristic of the urban and peri-urban dairy farming systems in and around the regional towns identified in the current study is that local dairy cows are numerically equally important in all the three systems, though this varied between the geographic regions studied.

On the contrary, studies on the characterization of the smallholder dairy systems have considered keeping local cows as characteristics of the rural system and not of the urban/peri-urban systems. Local breeds have received little attention from the national dairy cattle genetic improvement programs which has been taken virtually as synonymous to crossbreeding programs. Yet after decades of implementation of the national Holstein Friesian dairy cattle crossbreeding program, the proportion of the crossbred animals has not exceeded 1% of the national herd in Ethiopia .Thus the local dairy breeds are still prominent in the dairy genetics landscape of developing countries and thence continue to be an important resource in genetic improvement and dairy development strategies in all dairy farming systems excluding the systems located in and around the big cities. Besides their numerical importance, the indigenous cattle breeds are generally characterized as multipurpose animals, can be managed in low input production system and are adapted to marginal environments.

However, the current data on herd genetic structure with admixture of different breeds and genotypes including in the rural system which is believed to be the sanctuary for the indigenous genetic resources could be an indication of absence of well-planned and designed crossbreeding program, which could lead to indiscriminate crossing and threat to the adapted indigenous resources. The threat to the adapted indigenous resources is however more pronounced in the peri-urban/urban system according to the current data and elsewhere in Africa where, for instance, the proportion of crossbreds reached close to 40% in 2015 from 9% in 2004 in peri-urban system in Bamako. However, the local breeds are inherently low milk producers as they have been naturally selected for adaptive traits and not functional traits . Selective breeding could be the best option to improve the genetic merits of the indigenous breeds. However, to implement effective selection programs in village herds,there are constraints relating to the characteristics of smallholder village herd structure, infrastructures and attitudes of the public and private sectors towards selective breeding programs.

For instance in the current study local breeds are more important in West Gojjam zone than in West Sho zone which is located in the greater Addis Ababa milk shed where there is better access to breeding services and markets for fresh milk.Of the total 360 farms surveyed in West Shoa and West Gojam zones in this study, only 50.6% and 38.7% of the farms, respectively, conformed to the typical breeding characteristics identified by the analysis model for rural, peri-urban and urban dairy farming systems. This has an important implication in the designing and introduction of appropriate dairy development interventions. This is particularly relevant to the peri-urban system where the highest misclassification was observed. Identification of determinants of herd genetic structure regardless of the influence of farming systems showed that access to breeding services and land resources were the most important factors. The low proportion of crossbred cows in existing herds in the current study sites is contrary to farmers’ preferences for crossbred cows as elicited for the same study site and elsewhere in the highlands of Ethiopia.

The major constraint to meet farmers’ preferred dairy breeds and genotypes is the limitation in the AI service. The conception rate to first AI service has been reported to be as low as 27.1% , and the major challenge as reported by farmers is poor heat detection where AI is accessible, whereas access to reliable AI service has also been reported to be very low even in the peri-urban areas in an extensive study in the four highland regions of Ethiopia . The service is neither better around Addis Ababa where dissatisfaction has been expressed by about 46.7% of farmers surveyed . It has been argued that utilization and improvement of the desired crossbred population can only be efficient in situations where breeding programs with well-defined breeding objectives, breeding structure and infrastructure are developed,which is often lacking at smallholder level in the tropics.

The NUTMON determinants are mostly scale-neutral and can therefore be used to monitor nutrient balances at farm, regional, national and supranational levels.NUTMON is fed by a number of basic data, and by nutrient input and output data . Basic data include the surface area of the arable land, and the spatial patterns of land use systems.Nutrient input and output data are reflections of different processes, each of which has a certain value which is specific for a given LUS at a given time. A second monitoring exercise at a later stage may yield different results, which may be due to changes in the LUS, or changes in the individual nutrient input and output values. As the changes have either aggravated or ameliorated the nutrient balance, NUTMON can support decision-making in the interest of sustainable forms of agriculture. The environmental changes attributable to climate change are known to have direct and/or indirect effects on farmers thus on agricultural production in any region. Agriculture, for its numerous ecosystem services, has been an important component of human society.

Agriculture generates revenue for the government at the federal,state and local levels and as well serves as a means of livelihood by providing employment for farmers, marketers and processors of agricultural products. Like many countries, agriculture is a major sector of Nigeria’s economy, engaging over 70% of labour force and contributing about 40% to Gross Domestic Product . Agricultural production processes greatly rely on climate, thus a change in its composition is bound to have effects on the sector. Climate change has been a global issue affecting various agricultural production processes, including the producers: the farmers and their families. Climate change is the complete variation of the average state of the atmosphere over time, ranging from decades to millions of years in a region or across the entire globe, and can be caused by processes internal to the earth, external forces from space or anthropological activities. In recent time, especially in the context of environmental policy, climate change has often been referred to as the noticeable variation in environmental and atmospheric composition attributed to human activities .Climate change in the context of this study refers to the variation in the statistical distribution of average weather conditions over a prolonged period of time in any region of the world, such as the Niger Delta region of Nigeria.

Niger Delta region of Nigeria is densely populated and occupies about 12% of the total land mass of Nigeria with a land area of about 70,000 km2 out of which 2,370 km2 consist of rivers, creeks and estuaries, while stagnant swamp covers about 8,600 km2 . The region is divided into drier landward part where crop farming is the major agricultural activity and the seaward part which is characterized by extensive creeks and water bodies where fishing and aquaculture replaces crop farming as the dominant aspect of the rural economy. Economic activities of communities in the region are either land-based or water-based to include collection and processing of palm fruits, crop and animal farming, fishing and fish farming, forest resources utilization and trading of agricultural goods. The region occupies greater area of Nigeria’s most fertile land suitable for the cultivation of crops such as cassava, palm tree, rubber, yam, and many other crops while the availability of water bodies makes aquaculture feasible. The major agricultural produce in the region are cassava, cocoa, maize, melon, okra, palm oil, rubber and yam, in addition to domestication of animals such as fishes, goats, pigs, poultry, sheep, snail and rabbit.

The topical alteration in climate has become significant for worldwide discussion as it is likely human-induced.The major human related cause of climate change is the increase of Green House Gases in the atmosphere resulting from gas flaring, fossil burning and deforestation arising from clearing of land for agricultural and industrial uses, in addition to other human activities that have led to increased concentrations of GHG especially carbon IV oxide. The two primary sources of GHG emission are combustion of fuels and flaring of the natural gas, which is extracted along with crude oil. In 2009, the average CO2 emission in Nigeria was 74.14 million metric tons, which increased to 80.51 million metric tons and was predicted to drastically increase in the near future due to rising demand for products from crude oil . Anthropological activities have sped up climate change in recent time leading to the persisting impacts on agriculture and livelihoods in communities. For example, the Niger Delta region is reported to have over 123 gas flaring sites, making Nigeriaone of the highest emitters of GHG in Africa. Nigeria accounts for roughly one-sixth of worldwidegas flaring: Nigeria flares about 75% of her gas and all take place in the Niger Delta region. Some 45.8 billionkilo watts of heat are discharged into the atmosphere of the Niger Delta, from flaring 1.8 billion cubic feet of gas every day . Between 1970 and 1986, about 125.5 million cubic meters of gas was produced in the NigerDelta region of which about 102.3 million cubic meters were flared.

Plant cells cultures have a quick development cycle, have contained production and suitable for transient expression for rapid production of high protein yields of vaccines and prophylactic antibodies required during medical emergencies or outbreaks such as the Ebola virus disease in West Africa, but are the least scalable . Also, large number of bacteria introduced into the leaves increases the endotoxin load . Cell suspension cultures generated de novo by transformation of wild-type cells are always polyclonal because transformation is not 100% efficient and the transgenic cell lines can also undergo somaclonal variation, to generate cell populations with heterogeneous expression levels, necessitating screening and selection of the productive cell lines, optimizing the expression construct and culture conditions. Plantglycans also can affect the stability and functionality of recombinant proteins.

Plant-based systems still face one major bottleneck that needs to be overcome—their lower yields compared to mammalian cell cultures . The first licensed recombinant pharmaceutical protein derived from plants, Taliglucerasealfa was produced in plant cell suspension cultures. Vaccine against Newcastle disease virus produced in tobacco suspension cultures by DowAgrosciences, LLC, Indianapolis, USA was the first tobacco cell-based vaccine approved by the FDA against Newcastle disease virus in poultry. Physcomitrella patens suspension cultures were used to produce α-galactosidase for Fabry disease and βα for Gaucher disease by Greenovation Biotech BMBH company in Germany . Cells from tobacco, rice, medicago, carrot, tomato, sweet potato, soybean, Siberian and Korean ginseng are already used for production of Hepatitis B vaccine, Hepatitis antibody, Anti-HIV antibody, Norwalk virus capsidprotein, immunomodulators, growth hormone, lactoferrin, interferons etc.

Screening of high producing genotypes, selection of adequate medium, and optimization of the culture environment for plant cell culture may increase production. The plant virus-based expression systems can be used as transient expression systems, which use whole plants and avoid tedious regeneration processes. This is desired when rapid protein yield is needed and overcomes the difficulties of stable transformation. The plant virus-based expression systems can be either epitope presentation systems or polypeptide expression systems. Short antigenicpeptides are fused with the coat protein and are displayed on the surface of assemble dviral particles in epitope presentation systems. In polypeptide expression systems,whole unfused recombinant proteins are expressed and accumulated in plants. But insert size and limited host range are major constraints in this system. Recombinant plant virus-based nanoparticles made from genetically engineered isometric or helical viruses, with antigenic epitopes from pathogens elicit effective immune responses. Self-assembling coat proteins from viruses form the protein nanostructures free of genetic material and are referred to as virus-like particles , which are non-infectious and lack replication potential.

Non-enveloped helical plant viral capsids which are flexible and stable in terms of expressing foreign genes, are ideal platforms for epitope presentation system. Helical plant viruses, such as, bamboo mosaic virus , cardamommosaic virus , johnsongrass mosaic virus , papaya mosaic virus, papaya ring spot virus , plum pox potyvirus , potato virusX , potato virus Y , tobacco etch virus , tobacco mosaicvirus , and zucchini yellow mosaic virus have been genetically engineered to display immunogenic epitopes on their surfaces for vaccination against several diseases .Tobacco mosaic virus -based expression vectors are the most widely used vectors to produce foreign proteins in plants. First-generation viral vector retain infectivity in the plant, but have raised safety concerns. Second-generation viral vectors called viral “deconstructed” vectors have minimum of viral elements required for replication of the vector, and most DNA delivery to the target plant is via non-viral elements. A launch vector is developed with characteristics of Agrobacterium binary plasmid and plant virus expression vector. Tobacco Mosaic Virus is the viral vector widely used for the expression off oreign proteins in plants. Single-stranded positive-sense RNA genome of TMVen codes viral replicase genes for virus replication, while cell-to-cell movement protein , and coat protein genes are needed for recombination, effective spread and survival of the virus in the environment.

The target antigen gene that replaces CP gene which is inserted into a unique cloning site, under the transcriptional control of the coat protein sub-genomic mRNA promoter replicase,MP and viral replicase gene required for the replication of TMV gene was inserted between left and right border sequences of the Agrobacteriumbinary plasmid to form a launch vector, which is transferred into plant cells by agroinfiltration. Multiple single-stranded DNA copies of sequence between LB and RB are generated and released. Thus, viral vector is launched into plant tissue .These types of vectors have been used as an expression system for monoclonal antibodies due to their high and stable levels of protein expression.

Urban cities are lacking strategies, processes and technologies to provide stable, healthy, and safe food for growing populations. Intensive organic farming is another tool in sustainable agriculture but requires the application of bulk quantity of organic inputs for nutrition and pest control,which adds to the cost of production and possible environmental pollution. In such a case, the vertical farming in megacities plays a crucial role in providing food and nutritional security with resource efficiency.The cultivation of such high value crops under different innovation techniques results in increased cost of production because of the necessity for controlled environmental conditions, continuous supply and recirculation of good quality irrigation water and nutrients, and post-harvest handling costs until the product reaches the consumer. This would automatically increase the market price of the produce, which cannot be afforded by people with low-in come.Thus, it is essential to design innovative vertical farming technologies, which lower production costs without sacrificing product quality.

Microgreens are utilized as a suitable crop since they are rich in phytonutrients and vitamins while not necessarily needing external application of fertilizers. Microgreens are tender immature greens of vegetables, herbs, and grains providing intense flavors, vivid colors, and tender textures. Microgreens currently fetch a high price in the market because of its rich nutrition content and post harvest practices,such that the people with low income level cannot afford to buy them for enhancing their nutrition by adding them in their regular diet. This review is concerned about the production of highly nutritious and safe food with minimal post-harvest wastage by reducing the cost of production using containerized vertical farming technology. Vertical farming facilitates the production of high value crops with higher yield than obtained from conventional farming by efficient utilization of resources such as water, nutrients, space and time, thereby, reducing carbon footprint . This innovation utilizes both the horizontal and vertical spaces more effectively, thereby, producing higher yield per unit volume under controlled environmental conditions of temperature, light,carbon dioxide and humidity. There are different types of vertical farming innovations like hydroponics, aeroponics, and aquaponics where the nutrients are effectively utilized and monitored for physical and chemical parameters like quality, pH, and solubility in water.

Since vertical farming is experimented within a closed and controlled environment, sunlight as a source of light for carrying out photosynthesis is replaced by artificial lights with different spectra and intensities. In such a case, LED lights are more effective with high energy use efficiency and durability than traditional light sources like fluorescent lamps. Commercial hydroponics is a modern technology involving plant growth in nutrient solution without the use of soil as a rooting medium. This system involves the application of inorganic nutrients through irrigation water and recirculation of nutrient solution thereby avoiding wastage by leaching. The main advantages of this system include mitigation of problems related to soil such assoil-borne diseases, poor physical and chemical properties with decreased application of plant protection chemicals. Hydroponics results in enhancement of quality of fruits and flowers with precise application of nutrients. The disadvantages of hydroponics are higher installation cost for the soilless culture system,investment cost and technical skills needed to manage with them to obtain maximum yield and product quality within controlled environmental growing conditions.

Aeroponics represents the production of crops under air or mist environment without the use of soil as the rooting medium. In this system, the roots of the plants are exposed to the environment and can grow freely. The advantage of this system is that, it uses only 10% of the water needed for hydroponics and aquaponics because of the use of mist and hence the roots can access much more oxygen than in hydroponics and aquaponics. The disadvantages of this system are that a failure in the system would stop the flow of nutrient solution in the form of mist and may lead to the death of the crop . Aquaponics is a system which combines both hydroponics to produce crops and aquaculture to cultivate fish. The advantage of this system is that the fecal matter of fish would naturally become the organic fertiliser for the crops. This would eliminate the necessity for the solid waste disposal which would impose high management cost.

It is also essential to note that a range of fundamental natural resources, including land, water, air, biological diversity including forests, fish, etc., provide the indispensable base for agricultural production system and sustenance of agricultural ecosystems. Due to population growth and expansion of agricultural activities, the physical and functional availability of natural resources is diminishing. The latter can be attributed to loss of biodiversity, deforestation, loss of soil health, and water shortage. Given the multifunctional nature of agriculture,it is critical to consider linkages across ecosystems in which agricultural systems are embedded, as these have important implications for the resilience or vulnerability of these systems. These linkages between natural resource use and the social and physical environment across space and time are important issues for scaling out and the dissemination of agricultural knowledge, science and technology, with significant implications for sustainable development and the mitigation of adverse impacts.

It provides a source of employment for more than 60%of the population and contributes about 30% of Gross Domestic Product. The performance of the agricultural sector is determined by crop production,which depends on a large number of both edaphic and climatic factors such as endowment of soils, rainfall, temperature, and relative humidity. But recent concerns and findings indicate that these climatic variables are changing. Climate change refers to any variation in climate over time, whether due to natural variability or as a result of human activity. Climate change in the form of higher temperatures, reduced rainfall and increased rainfall variability, reduce scrop yields and net farm revenues and threatens food security in low income based economies including African countries . At the 10th and 38th Session of Inter-Governmental Panel on Climate Change Working Group IIin Yokohama, Japan, the world is warned that climate change’s impacts are leading to shifts in crop yields, overall decrease in yields, with the likelihood that global average surface temperature rising to 1.8 degrees to 4.0 degrees Celsius by2100. Climate variability will increase almost everywhere. Northern latitudes will experience more rainfall; many subtropical regions will see less.

In light of these,some indigenous communities are changing seasonal migration and hunting patterns to adapt to changes in temperature . Furthermore, IPCC report predicts that the climate change over the next century will affect rainfall pattern,river flows and sea levels all over the world. Studies show that agricultural yield will likely be severely affected over the next hundred years due to unprecedented rates of changes in the climate system. The accelerated increase in the greenhouse gases, concentration in the atmosphere is a major cause for climate change. Studies such as , predict that by the year 2050, the rainfall in Sub-Saharan Africa could drop by 10%, which will cause a major water shortage. This 10% decrease in precipitation would reduced rainage by 17% and the regions which are receiving 500 – 600 mm/year rainfall will experience a reduction by 50% – 30% respectively in the surface drainage.This has serious implications for Nigeria which is by far the world’s largest producer of yams, accounting for over 70 – 76 percent of the world production. According to the Food and Agricultural Organization report in 1985, Nigeria produced18.3 million tons of yams from 1.5 million hectares, representing 73.8percent of total yam production in Africa. According to 2008 figures, yam production in Nigeria has nearly doubled since 1985, with Nigeria producing 35.017million metric tons with value equivalent of US $5.654 billion.

Considering the findings above, there is need to preserve, boost and promote the agricultural sector especially root crop farming system as an alternative means of income for the Nigerian economy to cushion the economic shocks experienced by the fluctuating global oil prices in the face of the current economic recession. Investigated remote sensor technology for precision crop production. The findings of the study revealed that a combination of items was needed by farmers in utilizing sensory technology for precision crop production. examined climate change impacts and adaptation in rain-fed farming system using a modeling framework for scaling out climate smart agriculture. The potential for improving soil water productivity and improved water harvesting have been explored as ways of climate change mitigation and adaptation measures. The paper argued that this can be utilized to explore and design appropriate conservation agriculture and adaptation practices in similar agro-ecological environments, and create opportunities for out-scaling for much wider areas. studied the impact of climate change on yields for the four most commonly grown crops in Sub-Saharan Africa . A panel data approach was used to relate yields to standard weather variables, such as temperature and precipitation, and sophisticated weather measures, such as evapotranspiration and the standardized precipitation index .

The use of seasonal dambos for crop production is potentially associated with increase demission of GHGs such as nitrous oxide , carbon dioxide and methane . Nonetheless, the impact of dambo cultivation on GHG emissions is yet to be evaluated.The production Corresponding author. of rice, which is one of the major crops grown in dambos, has been associated with elevated GHG emissions, particularly CH4.Specifically,soil disturbance during dambo cultivation and application of fertilisers that influence microbial processes, soil organic carbon storage and turnover also affect GHG emissions from wetlands.However,to date there are no studies that have evaluated the use of conservation tillage practices on SOC storage and GHG emissions from dambos in Zimbabwe.In Zimbabwe, as in most of Sub-Saharan Africa, there are very few studies that have explored GHG emissions from cropped agricultural lands particularly dambos. There are a few reported studies the central and southern Africa regions e.g. Taylor et al.

The contributions of dambos of central and southern Africa to global CH4, carbon dioxide and N2O missions are mainly estimates as there have been very few measurements and there is a risk that a very important source of GHGs is being overlooked.This has been the case because of several reasons,among them; high research costs, limited funding, limitation of analytical infrastructure and trained personnel.The objective of the study was to quantify GHG emissions from seasonal wetland rice under different tillage systems, using static chambers. Northern China is always considered as a dry region comparing to the southern China. Especially in winter,a dry lasting cold weather dominates in the north.However,the northern China turned to be rich in precipitation in January 2018. The research region, called Region hereafter, is defined by the rectangle limitation comprising northern part of the farming-pastoral ecotone and Hulunbuir Grass-land, because both of the mentioned areas are economically relied on winter precipitations for crops growth, pasturage and tourism business. Up to date,many research are focused on the environment changes of such grassland ecosystem due to natural impact factors such as climate change, precipitation, grazing,fire and drought.The present research focuses on precipitation factor on the forest-grassland transition zone. Over the past 30 years from1988 to 2018, the maximum winter precipitation amount of the Region is no more than 100 mm, meanwhile in January 2018 that exceeds 400 mm.

This abnormal phenomenon attracts attention. For winter heavy precipitations, several studies are investigated worldwide. Single winter heavy precipitation occurred incentral Japan in January 2016. It is found that the occluding cyclones are the main cause of the heavy precipitations. Cold air out breaks, passing by of extra tropical cyclones are also causes of winter heavy precipitations in Japan. In addition, typical winter monsoon pressure patterns also contribute to the inland heavy precipitations in Japan. Along the coast of the Sea of Japan, local-scale depressions and local convergences caused by land breezes are factors for heavy winter precipitations . Studies on heavy winter precipitations in Japan caused by extratropical cyclones further provide information on root causes. The result is that the combination of the warm conveyor belt, the cold conveyor belt and the dry air intrusion is vital in the contribution of the heavy precipitations .Moving to areas above the southeast Canada and the northeast United States,North Atlantic Oscillation is the major cause of the heavy winter precipitation.The positive North Atlantic Oscillation induces less precipitations, while the negative North Atlantic Oscillation causes twice as many heavy precipitation events as the former .

In eastern Canada, studies show that the winter precipitations are poorly correlated with the North Atlantic Oscillation.In aspect of sea surface temperature influences, existing studies show that theme so scale of that can give a remote influence on atmospheric river land falling,leading to heavy precipitations along the west coast of North America . In addition, heavy winter precipitations in the west mountainous topography of America is also caused by the moisture originating from the Pacific, and transporting upwards through the mountains . For a heavy precipitation event in January 2008 in Iran, a deep low trough above the north of the Caspian Sea caused by a blocking system drives the thermal and moisture gradients . For summer heavy precipitations in Utah, both direct and indirect synoptic factors are important. Moreover, the humidity shift above the Atlantic Ocean plays acrucial role . In Romania, positive North Atlantic Oscillation and blocking phenomenon over the Atlantic-European sector can cause winter precipitations to decrease . Global warming is another key contributor to extratropical cyclones,leading to the increase of the precipitation intensity .

However, to date, no study has yet estimated leaf photosynthetic capacity using a DNN model based on leaf reflectance. Hence, the objectives of this study are to assess the feasibility of predicting the photosynthetic capacity from leaf reflectance in cool–temperate deciduous forests by employing DNN models; to assess the performance of DNN models across different leaf types and different temporal scales; to evaluate whether including other leaf traits would improve the estimation of leaf photosynthetic capacity using DNN models. This study explores the potential of deep learning for predicting photosynthetic capacities quantitatively in different leaf types and during different growing periods in cool–temperate deciduous forests. A DNN model is generally composed of an input layer, an output layer, and several hidden layers placed between them, and each layer contains a number of neurons. In this study, leaf reflectance data were considered as predictors of Vcmax and Jmax when constructing the deep neural network.

The workflow is illustrated in Figure 2. The entire dataset was then randomly divided into training data and test data , while the training dataset was further arranged to be in proportion to the validation data. Specifically, the networks had the following architecture: an input layer, seven hidden layers with 16, 32, 64, 128, 256, 128, and 64 neurons, respectively, and an output layer, with the nodes being fully connected. The loss and optimization functions selected were the mean square error and the Adam optimizer, respectively. The number of training epochs was defined using early stopping; the networks were trained for 500 epochs, with the patience equal to 20 epochs, to minimize the loss function until the minimum error was achieved to prevent overfitting. Furthermore, dropout , which is a regularization technique that randomly and temporarily removes a fixed proportion of different neurons and their respective connections from the network in each training step, was also used to avoid complex co-adaptations on training data, therefore reducing overfitting. The deep neural networks were builtand trained with the TensorFlow backend, using the Keras library in RStudio . To improve the generality and predictive performance of the DNN model, a bootstrap approach was applied for the training dataset in this study.

Bootstrapping is a resampling method that samples independently with replacement from a sample dataset with the sample size, which reduces biases and strengthens the robustness, especially when the number of samples is limited . Specifically, we randomly sampled the training set with replacement k times; the maximum k value was set to 50 and the best k value was selected based on the mean squared error. The DNN model was fitted using a bootstrap sample each time and prediction values fromFurthermore, we explored the robustness of the DNN models for predicting the photosynthetic capacity with different leaf groups. The modeling performances for Vcmax and Jmax of the DNN model for sunlit leaves were much higher than those for shaded leaves. The differences in leaf groups can be explained by the differences in their responses to the photosynthesis process and/or the changes in leaf properties such as the leaf mass per area, and the light environment throughout the vertical profile. Taking the sunlit and shaded leaf groups into consideration is helpful for improving the estimation of carbon and water fluxes. In addition, the performance using the DNN models in estimating Vcmax and Jmax was notably the best during the leaf flushing period, followed by the senescence period, with the poorest performance occurring during the maturity period.

As reported by previous studies, leaf flushing and senescence are accompanied by a strong increase and decline in photosynthetic capacity, while leaf maturity is relatively stable with minor changes . A more likely explanation is that the spectra–photosynthetic capacity linkages could vary with leaf age. The results suggest that including as many axes of variation as possible is critical in tracing the photosynthetic capacity using spectral information.Our results showed that using only leaf hyperspectral reflectance, it is possible to capture a large variety of photosynthetic traits. However, combining other leaf biophysical/biochemical traits could further improve the estimation accuracy of photosynthetic traits using DNN models, since our results clearly indicated that the estimation accuracy of Vcmax from reflectance using DNN models was much improved by the addition of the leaf chlorophyll content for sunlit leaves. Leaf chlorophyll is an important component of the photosynthesis machinery that harvests light and transports electrons to support the production of the biochemical energy necessary to drive photosynthesis , and it is an important indicator of physiological status .

The main stem diameter, number of branches, and number of nodes were significantly different among different growing periods and different seeding patterns . However, only the growth stage had a significant effect on the main stem height , whereas the seeding pattern showed no significant effect on it . The monoseeding treatment resulted in the thickest main stem diameter and the highest number of branches and nodes compared with those in the triple-seeding treatments . Non-significant differences were observed in the main stem diameter, number of branched and the number of nodes between the double- and triple-seeding treatments. The effect of the growth stage, treatment, and interaction between year and growth stage, and growth stage and treatment, was significant for the main stem height, main stem diameter, number of branches, and number of nodes , whereas only the year had a significant effect on the main stem height, main stem diameter, and number of nodes . However, the interaction of year × growth stage × treatment had no significant effect on the main stem height, main stem diameter and number of branches but did affect the number of nodes .

The present study revealed that monoseeding might be a useful strategy to minimize the SAR of peanut at the same population density as used for the traditional seeding methods and thus increase peanut yield. Monoseeding decreased the main stem height but increased the main stem diameter, number of branches and nodes, SPAD values, and Pn, which is similar to the results in both herbaceous and woody species . Higher yield was achieved through increasing the number of pods per plant, 100-pod weight, and shelling percentage in the monoseeding treatment. Furthermore, the expression levels of SAR genes were also found to be associated with monoseeding. Many researchers have found that yield can be increased by minimizing the SAR in crops . Here, main stem height decreased but main stem diameter, number of branches, and number of nodes increased compared to the traditional seeding patterns , which reduces the competition among plants. Similarly, another study revealed that monoseeding reduces the competition among individuals at the same population density . Moreover, the leaf and root dry biomass were simultaneously reduced in the multiple seeding groups as a result of the reallocation of resources due to the low R/FR ratio.

We found that the dry matter of different organs in the monoseeding treatment was higher than that in the double- and triple-seeding treatments. This result may be due to the increased reallocation of assimilates to the organs rather than stem elongation compared with that under the traditional seeding patterns. Leaf chlorophyll content reduction is another phenomenon of SAR . When the R/FR ratio is low, chlorophyll synthesis decreased and the plant accumulates less chlorophyll, which is partly mediated by phytochromes. The response of phytochromes to FR and Rradiation plays an important role in adjusting the SAR at high population density . Phytochromes are encoded by a small gene family in angiosperms, which interact with bHLH transcription factors to control many aspects of photomorphogenesis . Under shaded conditions, the pool of PIFs increases, which regulates the gene expression that promotes the SAR . However, the expression of PIF 1 and PIF 4 under monoseeding signifificantly decreased compared to that in the double- and triple-seeding treatments in our study. This result indicated that monoseeding might reduce the shade for peanut neighbors, enabling plants to absorb more R light and thereby inhibiting the SAR at the same population density as used for the traditional seeding patterns. The decrease in PIFs observed at high PAR was accompanied by an increase in Phy B, which plays a major role in SAR inhibition . We also found that expression of Phy B was increased and PIF 1 and PIF 4 expression levels were decreased in the monoseeding treatment, thereby inhibiting the SAR in peanut.

These results are in accordance with those of Franklin regarding Arabidopsis. Therefore, the regulation of SAR under monoseeding could be due to the decreased expression of PIF 1 and PIF 4 and the increased expression of Phy B. However, in the double-seeding treatment with low R/FR, the phytochrome photo-equilibrium shifted to the inactive Pr forms, which no longer interact with PIF 4 and promote the SAR. Phy A is the only phytochrome to rapidly decrease at a high R/FR ratio . Previous research indicated that Phy A can reduce the SAR at a low R/FR ratio . In our study, the expression of Phy A significantly decreased in the monoseeding treatment compared to that in the double-seeding treatment, indicating that plants under monoseeding might receive more R radiation from sunlight and convert it into the biological active Pfr form, which interacts with PIF 4, triggering additional phosphorylation and alleviating SAR. PAR was detected initially as an early repressed gene in the photoreceptor signaling pathways and acts as a negative factor of the SAR . At a low R/FR ratio, the expression of PAR 1 and PAR 2 increases, which suppresses several auxin-mediated SARs .