Variation of Physical and Chemical Properties of Soils under Different Cropping Systems in the Watershed of Kpocomey, Southern Benin

Soils degradation is one of the constraints in food security achievement in Benin. This study aimed at assessing the effect of cropping systems and slope on soil physical and chemical properties in the watershed of Kpacomey located in the Aplahoué district. Soil samples were collected from three parallel transects along the slope. Sampling was carried out under different treatments combining cropping systems (Maize-Cassava, pure Palm grove, Palm grove-Maize-Cassava and Teak Plantation) along with slope levels (low slope, medium slope and high slope degree). The impact of cropping systems and slope on soil properties was assessed by determining the physical and chemical parameters. The cropping systems significantly (p < 0.05) influenced soil bulk density, root biomass, soil acidity and soil organic matter. The lowest soil bulk density (1.38 g/cm3) was recorded under the Palm grove-Maize-Cassava cropping system while the highest (1.47 g/cm3) was obtained with pure Palm grove cropping system. Root biomass was more abundant (0.28%) with the pure Palm grove cropping system. However, root biomass was significantly (p < 0.05) influenced by slope. Soil crusting resulted in no significant influence (p > 0.05) on the effect of cropping systems and slope. Moreover, cropping systems resulted in significant effects (p < 0.05). Soil organic matter and soil-assimilated phosphorus content were significantly influenced by the effect of the slope. These findings indicated that cropping systems and slope are significant drivers in soil degradation in the Kpacomey watershed and bringing out cropping systems that best aim at soil conservation.

Mineral Fertilizer Use for Optimal Groundnut Production in the Sudano-Guinean and Sudanian Zones of Benin

Abstract This study aims to determine the optimal N, P, K, Mg and Zn rates for groundnut production on Ferric and Plintic Luvisol in the Sudano-Guinean and Sudanian zones of Benin Republic. Two years (2018 and 2019) experiment was carried out in the municipality of Ouessè in the Sudano-Guinean zone and Bembèrèkè in the Sudanian zone. The tested nutrient doses were N (0, 20 and 40 kg⋅ha−1), P (0, 25 and 50 kg⋅ha−1), K (0, 20 and 40 kg⋅ha−1), Mg (0, 15 and 30 kg⋅ha−1) and Zn (0, 4 and 8 kg⋅ha−1). The Box and Behnken rotating design is used to define the N, P, K, Mg and Zn rate combinations leading to 46 combinations. A completely randomized bloc design was setting up considering farmers as replication. In total, four farmers’ fields were selected. A one-way analysis of variance is carried out on yield data, using the linear mixed-effect model. Response surface analyses were used to determine the optimal doses for each N, P, K, Mg and Zn. Nodule production (6.5 times higher than the control), number of gynophores (2.8 times higher than the control) and root length (19.2 ± 0.2 cm) of groundnut plants were significantly (p = 0.0001) improved with nutrient application. The response surface analysis shows that treatments N-P-K-Mg-Zn of 16.01-20.18-6.70-5.65-2.47 (in the Sudano-Guinean zone) and 13.1-25.07-11.47-0-1.82 (in the Sudanian zone) are the optimal rates that have induced optimal yield of 2.1 t⋅ha−1 (i.e. 2.5 times the yield in the farmers’ field) pod yield and the best return on investment per hectare. Nevertheless, for a sustainable groundnut producproduction, treatment 13.1-25.07-11.47-20-1.82 is suggested as regular K input is required for the respect of the fertilization laws.

Effect of Climate Variability on Yams (<i>Dioscorea spp</i>.) Production in Central and Northern Benin

Climate change poses an important constraint to agricultural sector and food security in tropical African countries dominated by rain-fed agriculture. This research focuses on the effects of climate variability on yam production in central and northern Benin. Daily climate data such as temperatures, precipitation, potential evapotranspiration, relative humidity and insolation from 1981 to 2016 were collected at the direction of METEO-Benin. A survey was then conducted with 351 producers to collect their perceptions of the effect of climate variability on the yams production. Descriptive statistics, principal component analysis (PCA) followed by trend analyses, Lamb index calculations and the agro-climatic stress index were carried out. The distribution of rain during the yam cycle (91.5% of those surveyed), the ambient temperature (84.9%), insolation (83.5%), the amount of rainwater that fell during the rainy season (82.2%) and the harmattan (53.3%) are perceived by sociolinguistic groups as climatic factors affecting the growth, the tuberization and yield of yams according to the producers. The results indicate an upward trend in temperature over the period 2001 to 2016 in the transition zone (28.4°C) and in the Northeast (27.76°C) and over the period from 2001 to 2011 in the North-West of Benin (27.71°C), where the average annual temperature during these periods is higher than normal (27.82°C in the center, 27.44°C in the Northeast and 27.42°C to the northwest). This research also shows an instability of the rains with a regular decrease in the rainfall in the Centre and the North-East of the country. The agro-climatic stress index (ISA) and above all the annual rainfall constitute the main climatic factors which determine the yield of yam in the various growing areas in Benin. The average annual temperature and that of January in the transition zone, the rains of January and April in the North-East zone and the relative humidity in the North-West zone also probability determine the yield of the yam.

Modelling of Sorghum (<i>Sorghum bicolor</i>) Growing Areas under Current and Future Climate in the Sudanian and Sahelian Zones of Mali

Climatic variability is one of the main constraints of agriculture in Mali, which will certainly affect long-term sorghum yields. The objective of the present study was to assess the effect of climate variability on sorghum production areas by 2050 in the Sudanian and Sahelian zones of Mali considering three climate scenarios: current scenarios (RCP 2.5), optimistic scenarios (RCP 4.5) and pessimistic scenarios (RCP 8.5). Therefore, 11,010 occurrence points of sorghum (Sorghum bicolor) were collected and associated with the environmental variables of the three climatic scenarios according to the maximum entropy approach (Maxent). Sorghum environmental data and points of occurrence were obtained from AfriClim and GBIF databases, respectively. The correlations carried out and the Jackknife test allowed us to identify variables that contributed more to the performance of the model. Overall, in the Sudanian zone, the suitable area for sorghum production which currently represents 37% of the area of the district of Koulikoro will increase up to 51% by 2050 considering the optimistic scenario (RCP 4.5). Furthermore, considering the pessimistic scenario (RCP 8.5), the suitable zones for sorghum production will experience a decrease of 10%. In the Sahelian zone, the suitable zones for sorghum production that represent 55% of San district area considering the RCP 2.5 scenario will experience a decline of 24% by 2050 considering both the optimistic (RCP 4.5) and pessimistic (RCP 8.5) scenarios. It is suggested to carry out investigations on potential sorghum yield prediction in both study areas in order to identify suitable production areas of the crop in the near future (2050) and long term (2100) as adaptation strategies and resilience of farmers to climate change.

Modelling the Current and Future Spatial Distribution Area of Shea Tree (<i>Vittelaria paradoxa</i>C. F. Gaertn) in the Context of Climate Change in Benin

In Benin, Shea tree (Vitellaria paradoxa) is one of the agroforestry species of great socio-economic importance for local populations. Given the actual variation in the climate parameters, it is necessary to anticipate the future spatial distribution of Shea trees as an adaptation strategy and for designing relevant conservation strategies. The aim of the present research was to evaluate the influence of climate change on the distribution areas of Shea trees in Benin. Occurrence data consisting of geographic coordinates of Shea trees in Benin as well as bioclimatic variables were recorded. Furthemore, additional presence points were collected from the Global Biodiversity Information Facility database website. Current and future environmental data for the study area were obtained from the Africlim website. Bioclimatic variables (moisture and temperature), monthly maximum and minimum temperatures and annual rainfall were collected from Worldclim synoptic stations website for the period 1970-2000. The aridity index was created from the potential evapotranspiration (PET) and annual rainfall, using spatial analysis tools of ArcGIS. The impact of current and future environmental conditions on favourable Shea trees’ growing area was assessed following the maximum entropy (MaxEnt) approach under two climate scenarios (RCP 4.5 and RCP 8.5). Under the current climate conditions, 80% of Benin territory and 79% of the protected areas were highly favourable for Shea trees growing and conservation. However, all climate scenarios projected the significant decrease of 14% to 19% of the distribution of favourable for Shea tree growing area and 26% to 30% of the protected areas by 2055 in favour of non-favourable for the trees’ distribution. The protection of habitats favourable for the species development, coupled with a quick restoration of the species through the use of appropriate vegetative propagation techniques are required to sustain the species’ conservation in Benin and maintain farmers’ livelihood.

Decomposition and Mineralization Effect of Various Sources of Pig Manure on Water Quality and Nutrients Availability for Agro-Fish System in Benin

In spite of the relevance of current studies on the importance of organic fertilizers such as animal manure in improving the health of ecosystems, little is known about the biochemical mechanisms affecting the availability of nutrients released from the organic fertilizer in water. A litter bag study during 6 weeks was carried out in pots containing 25 liters of water with 15 g of pig dejections as organic fertilizers. The experimental design was a completely randomized block design with three replications. The treatments consisted of dejections of pigs nourished with: recommended diet composition T1, partially improved diet with Azolla filiculoides T2, improved diet with Azolla filiculoides T3, improved diet with cereal bran T4. A control treatment without dejection (T0) was considered in the study for comparison purpose. Four pigs per type of diet were considered leading to 16 white landrace pigs of six months age followed for dejection collections. Strong release of nutrients for better yield for agro-fish system was obtained in the manure T1 with ??(10.85 ± 0.00) mg/L;?( 0.011 ± 0.00) mg/L;?(2.13 ± 0.07) mg/L and K+ (10.76 ± 0.57) mg/L;Ca2+ (2.92 ± 0.11) mg/L and Mg2+ (2.53 ± 0.00) mg/L followed by manure T3 and T4 with high N content. The relatively low ratio C/N (14.25) for T1 and (15.84) for T3 induced more nutrients releasing. This study showed an important N loss probably due to microorganism activities which fluctuate nutrient availability. Also significant correlations were noted between the nutrient dynamics in water and physicochemical parameters showing the effect of abiotic factors on organic matter decomposition and mineralization which depend on microbial activities in water and pig manure composition.

高光谱遥感在农作物长势监测中的应用

该研究是加拿大Saskatchewan Scott农作物轮作系统(ACS)研究的一部分。研究始于1994年,历时18a,评价9个可耕种农作物产量系统的可靠性。由3种处理水平(organic,reduced,high)和3种作物多样性水平(low,diversified annual grains,diversified annual perennials)结合而产生的9个农作物产量系统,被用于监测和评价加拿大牧场不同处理和不同作物种植轮作下可耕种农作物的产量。在2003年生长季共收集了3次叶面积指数和光谱反射率的数据:生长季前期(6月)、生长季旺盛期(7月)、生长季后期(8月)。叶面积指数是由LAI-2000植物冠层分析仪监测的,光谱测量是由覆盖了350-2500 nm波长范围共2215个波段的ADS便携式高光谱仪完成的。结果显示,光学测量可以用于监测农作物生长状况的差异。从生长季的早期到中期,光谱和叶面积指数在不同处理下有显著差异。7月中期是用遥感资料监测农作物长势的最佳季节;红光波段与近红外波段反射率的比值和基于这两个波段构造的归一化植被指数,是检测农作物长势的最佳植被指数。