19Establishing balanced nutrient requirements for maize (Zea mays L.) in the Northern Nigerian 20 Savanna is paramount to develop site-specific fertilizer recommendations to increase maize 21 yield, profits of farmers and avoid negative environmental impacts of fertilizer use. The model 22 QUEFTS (QUantitative Evaluation of Fertility of Tropical Soils) was used to estimate balanced 23 nitrogen (N), phosphorus (P) and potassium (K) requirements for maize production in the 24 Northern Nigerian Savanna. Data from on-farm nutrient omission trials conducted in 2015 and 25 2016 rainy seasons in two agro-ecological zones in the Northern Nigerian Savanna (i.e. 26 Northern Guinea Savanna "NGS" and Sudan Savanna "SS") were used to parameterize and 27 validate the QUEFTS model. The relations between indigenous soil N, P, and K supply and 28 soil properties were not well described with the QUEFTS default equations and consequently 29 new and better fitting equations were derived. The average fertilizer recovery fractions of N, P 30 and K in the NGS were generally comparable with the QUEFTS default values, but lower 31 recovery fractions of these nutrients were observed in the SS. The parameters of maximum 32 accumulation (a) and dilution (d) in kg grain per kg nutrient for the QUEFTS model obtained 33 were respectively 35 and 79 for N, 200 and 527 for P and 25 and 117 for K in the NGS zone 34 and 32 and 79 for N, 164 and 528 for P and 24 and 136 for K in the SS zone. The model 35 predicted a linear relationship between grain yield and above-ground nutrient uptake until yield 36reached about 50 to 60% of the yield potential. When the yield target reached 60% of the 37 potential yield (i.e. 6.0 tonnes per hectare), the model showed above-ground nutrient uptake of 38 2 19.4, 3.3 and 23.0 kg N, P, and K, respectively, per one tonne of maize grain in the NGS, and 39 17.3, 5.3 and 26.2 kg N, P and K, respectively, per one tonne of maize grain in the SS. These 40 results suggest an average NPK ratio in the plant dry matter of about 5.9:1:7.0 for maize in the 41 NGS and 3.3:1:4.9 for maize in the SS. There was a close agreement between observed and 42 parameterized QUEFTS predicted yields across the two agro-ecological zones (R 2 = 0.70 for 43 the NGS and 0.86 for the SS). We concluded that the QUEFTS model can be used for balanced 44 nutrient requirement estimations and development of site-specific fertilizer recommendations 45 for maize intensification in the Northern Nigerian Savanna.46

HighlightsNew and better fitting QUEFTS’ prediction equations for indigenous soil N, P, and K supply were developed for the Northern Nigerian Savanna.A good correlation was observed between the observed and parameterized QUFETS predicted maize grain yield.The QUEFTS model predicted a balanced N, P, K uptake to linearly increase with grain yield until 50-60% of the potential yield.The QUEFTS model is a suitable tool for site-specific nutrient recommendations in maize in the Northern Nigerian Savanna.

The Decision Support System for Agrotechnology Transfert (DSSAT) is a software comprising crop simulation models. The aim of this study was to: Calibrate the CROPGRO-cowpea model of DSSAT for four cowpea varieties, and Validate the model using a data set collected under drought stress For this purpose, experiments were carried out in 2020 and 2021 dry seasons in Burkina Faso at Kamboinsin in the Centre of Environmental and Agricultural Research and Training (CREAF). The model calibration was done using data including days to 50% flowering, days to maturity, above-ground biomass, and grain yield per hectare collected from an experiment without water and nutrient stress, and the GenCalc software was used for estimating the genetic coefficients of the varieties. Data from two drought stress treatments, such as D1: drought at seedling stage, and D2: drought at flowering stage, were used for validating the model. The results of the calibration showed that the model excellently simulated the days to flowering with a normalized root mean square error (nRMSE) of less than 10% and a high degree of agreement for all the varieties. The simulation of the days to physiological maturity was excellent for 50% of the varieties (nRMSE<10%) and good for the others (10 < nRMSE < 20%). The simulation of the grain yield per hectare ranged from excellent to good. Poor prediction of the above-ground biomass was attained for 75% of the varieties (nRMSE ≥ 40%), while the fair simulation was recorded for 25% (nRMSE=27%) during the model calibration. The statistics of the validation process showed an excellent simulation of the days to flowering (nRMSE= 1.85%; R2=0.98; d-index=0.99) and a good prediction of the days to maturity (nRMSE=13.82; R2=0.87; d-index=0.53) for all the varieties. Simulated above-ground biomass was in poor agreement with the observed values (nRMSE=106.62%; R2=0.92; d-index=0.36). Fair prediction of the grain yield by the model was achieved during the validation (nRMSE = 27%). From these results, it can be concluded that the DSSAT model can be considered an efficient tool for predicting cowpea phenology, growth, and yield in optimum conditions of development. However, in drought stress conditions, the sensitivity or tolerance status to the drought of the variety can reduce the accuracy of the grain yield prediction by the model.

This article presents a review on the opportunities available in the drier savannahs of Northern Nigeria for the production of soil organic amendments to improve soil productivity and enhance carbon sequestration through a synergistic system. The use of soil organic amendments in the farming systems of the drier savannas of Nigeria is below optimal principally because of the low level of awareness among small‐holder farmers in the region and production cost/benefit disadvantage. Given the large quantities of organic wastes generated in expanding cities in the region and non‐feed agricultural waste resources from rural and peri‐urban areas, there is potential to approach waste management from the perspective of waste conversion in a synergistic approach to minimize production cost especially in the form of energy savings. This will enhance the availability of materials such as biochar and compost which have been advocated as two principal materials with properties that can improve poor soils, such as those in the region under consideration. When coupled with risk management and extension strategies targeting farmer education, the products may be adoptable across the vast arable fields in the region thereby maximizing use advantage.

The large-scale plantation of Neem trees have been used in the Sudan and Sahelian region of Nigeria to combat desertification, deforestation, soil erosion, and reduce excessive global warming. The research was aimed to investigate the effect of Neem tree canopy (Azadirachtaindica) on soil Bulk density and soil porosity in Kano University of Science and Technology Teaching and Research farm, Gaya, Kano State. The farm was divided into four quadrants, and three Neem trees were selected from each quadrant. Soil samples were collected at distances of 2m, 4m, 6m (from tree girth), and outside the Neem tree shades and were analyzed in the laboratory. Core samples were also taken from each sampling point and were analyzed for bulk density determination. The results of Bulk density show a significant difference (P<0.05) across the four quadrants, with Quadrant 4 having the highest Bulk density mean value (1.61gcm-3). There is no significant difference (P>0.05) in Bulk density across distances from Neem tree girth. However, bulk density mean value was found to be increasing across distances of 2m, 4m and 6m from tree girth. The results of soil porosity show no significant difference (P>0.05) across the four quadrants and across distances from Neem tree girth. The porosity mean values outside shade is found to be the least (36.5%). The low Bulk density mean values and high porosity mean values of the area found under the Neem tree canopy is suitable for alley cropping as well as possess good aggregate stability, hence, reduces the susceptibility of the soils to erosion. Further research should be done to study the macro and micronutrients composition of soils under the Neem tree canopy, which will aid in fertility management of the soils.