Response of the Maize Variety EV87-28 to a Fertilization Strategy Involving Indorama Granular Urea on Ferralsol in the Central Ivory Coast

In Côte d’Ivoire, the decline in soil fertility strongly impacts the productivity of maize (Zea mays L.) on heavily leached ferralitic soil. In this study, the general objective was therefore to improve the productivity of maize EV87-28 on the Ferralsols in pre-forested areas during different cropping seasons. Eight (8) micro-plots were set up according to a total randomization device with three repetitions. Two factors were studied: nitrogen fertilizer modalities (main factor) and crop season (secondary factor). Growth, flowering and yield parameters were measured and analyzed. The results showed that there was no interaction between the nitrogen fertilizer factor and the cropping season factor. In addition, this study showed the short rainy season had the most positive impact on growth, flowering and yield parameters than the long rainy season. The results also showed that the different nitrogen fertilizer modalities had no statistically different effects on growth, flowering and yield parameters. However, quantitative differences were reported, highlighting one nitrogen fertilizer modality, which is the combination of urea granule + farm manure (75% urea indorama granules and 25% farm manure). The combination of urea granule + farm manure (75% urea indorama granules and 25% farm manure) had the best effect on corn grain yield. So, the combination of urea (75%) and manure (25%), that resulted in yield gain, could be recommended for corn fertilization during the small rainy season.

Effects of Calcium and Magnesium on Phosphorus Availability in Ferralsols and Rice Production in Forest Zones of Côte d’Ivoire

Phosphorus bioavailability has long been a recurring problem in tropical acid soils. A pot experiment was carried out during three (3) successive rice production cycles at Adiopodoumé to evaluate the response of the NERICA 5 rice accession to various doses of calcium, magnesium and phosphorous. The experiment was conducted using a randomized split-plot design. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg·Ca·ha-1) and magnesium sulfate (0, 25, 50 and 75 kg·Mg·ha-1) and Togo natural phosphate (0, 25, 50 and 75 kg·P·ha-1) were determined at each production cycle. The results showed that single-dose natural phosphate supplementation for three cropping cycles resulted in an average enrichment of around 2 mg·P·kg-1 after each trial following its continuous dissolution, with an increase in DSP (33.31% to 70.52%). The study revealed one strategy for managing and enhancing native P with cations and another for exogenous P: there would be a synergy of Ca/Mg on native P, whereas an antagonism would characterize the two parameters in phosphate fertilization.

Calcium-Magnesium Ca/Mg Ratios and Their Agronomic Implications for the Optimization of Phosphate Fertilization in Rainfed Rice Farming on Acidic Ferralsol in the Forest Zone of Ivory Coast

This study is a contribution to improving rice productivity on acidic plateau soils of the tropical rainforest zone. It is based on taking into account the cationic balances of the soil in order to optimize the phosphorus (P) nutrition of rice on these acidic soils, where this nutrient constitutes a limiting factor for agricultural production. Three (3) pot trials were conducted in Adiopodoumé in the forested south of Côte d’Ivoire. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg Ca ha−1) and magnesium sulfate (0, 25, 50 and 75 kg Mg ha−1) were evaluated on the response of NERICA 5 rice at doses 0, 25, 50 and 75 kg P ha−1 of natural phosphate from Togo, applied only once at the start of the experiment. Additional fertilizers of nitrogen (N) (100 kg N ha−1) and potassium (K) (50 kg KCl ha−1) were added to each of the tests in a split-plot device. The test results revealed a paddy production potential of approximately 3 to 5 t⋅ha−1 for NERICA 5 on an acidic soil, under the effect of the interaction of P, Ca and Mg. The quadratic response of rice yield to the doses of these fertilizers would be more dependent on their balance, itself influenced by Ca nutrition. For the sustainability and maintenance of rice production in agro-ecology studied, it was recommended doses of 38 kg Ca ha−1, 34 kg Mg ha−1 in a Ca/Mg ratio (1/1) with intakes of 41 kg P ha−1, overall in a ratio 1/1/1 (P/Ca/Mg) more favorable to the availability of free iron considered a guiding element of mineral nutrition. Thus, these promising results should be confirmed in a real environment for better management of the fertilization of rice cultivated on acidic plateau soils in Côte d’Ivoire.

Sensitivity Study of the RegCM4’s Surface Schemes in the Simulations of West Africa Climate

Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature and precipitation were analyzed. The purpose of this study is to assess the performance of RegCM4 coupled with the new CLM4.5 Land surface scheme and the standard one named BATS in order to find the best configuration of RegCM4 over West African. This study could improve our understanding of the sensitivity of land surface model in West Africa climate simulation, and provide relevant information to RegCM4 users. The results show fairly realistic restitution of West Africa’s climatology and indicate correlations of 0.60 to 0.82 between the simulated fields (BATS and CLM4.5) for precipitation. The substitution of BATS surface scheme by CLM4.5 in the model configuration, leads mainly to an improvement of precipitation over the Atlantic Ocean, however, the impact is not sufficiently noticeable over the continent. While the CLM4.5 experiment restores the seasonal cycles and spatial distribution, the biases increase for precipitation and temperature. Positive biases already existing with BATS are amplified over some sub-regions. This study concludes that temporal localization (seasonal effect), spatial distribution (grid points) and magnitude of precipitation and temperature (bias) are not simultaneously improved by CLM4.5. The introduction of the new land surface scheme CLM4.5, therefore, leads to a performance of the same order as that of BATS, albeit with a more detailed formulation.

Rice Growth and Yield in Humid Forest of Cote d＇lvoire as Affected by Different Sources of Phosphates in Ferralsol

There is immobilization of inorganic P （phosphorus） fertilizer becoming unavailable to plants and declining yield over cropping seasons is occurring in rice agro-ecology of humid forest. The performances of indigenous PR （rock phosphates） from Ma （Mali）, Burkina Bu （Faso）, Ni （Niger）, To （Togo） and Senegal including that of Pa （Thies） and Ta （Taiba） were tested applying 200 kg.P2O5.ha-1 and 400 kg.P2O5.ha-1 once for three cropping seasons while TSP （triple super phosphate） was applied every season at 60 kg.P2O5.ha-1 and 120 kg-P2O5.ha-1. No P-fertilizer treatment was the control plot and WAB 56-104 was sown as rice variety. No significant difference was observed between the overall mean values of plant height, tiller and panicle numbers according to P-sources likewise for the grain yield when comparing that of 60 kg.P2O5.ha-1 （TSP） vs. treatments of PR while, the treatments Pa, Ta and To significantly induced greater grain yield than 120 kg.P2O5.ha-1 as TSP. Moreover, declining yield in the third cropping year was greater （75%） with TSP than for To, which was not significantly impacted by the number of cropping seasons. Applying 200 kg.P2O5.ha-1 of To was suggested as strategy for sustaining rice production on Ferralsol of west Africa.

Enhancing Rice Productivity and Soil Nitrogen Using Dual-Purpose Cowpea-NERICARice Sequence in Degraded Savanna

ISFM （integrated soil fertility management） involving annual sequencing of dual-purpose early-maturing first crop of cowpeas with biomass incorporation before seeding second crop of early-maturing NERICA （New Rice for Africa） was evaluated to enhance rice productivity and soil-nitrogen. Five dual-purpose early-maturing cowpea cultivars and local cultivar （Katche） were seeded early in the wet season in five farmers＇ fields at Ouake （9046＇ N, 1°35′ E, highly degraded-savanna）, Benin. After pod harvest, cowpea residues were minimally worked into the soil using minimum tillage with hand-hoe and seeded with early-maturing, resilient NERICA8 rice that received either 20 kg N/ha or zero-N. Cowpea grain yield averaged 0.1-0.3 Mg/ha, and mean aboveground cowpea biomass produced and recycled was 0.54-0.64 Mg/ha among best cultivars （IT97-568-11 and IT89KD-288）. NERICA8 seeded after cowpea cv. IT97-568-11 and supplied with 20N gave the greatest grain yield of about 2.0 Mg/ha, accounting for 500% heavier grains than fallow-rice rotation with zero-N. Mineral-N dynamics monitored under NERICA8 in year 2 showed that previous IT97-568-11 plots had the highest mineral-N at tillering which persisted till panicle initiation stage. The adoption of an ISFM comprising annual cowpea-NERICA sequence by smallholder rice farmers could enhance productivity and improve N-supply in fragile savannas.