RESPONSE OF COWPEA (Vigna unguiculata) VARIETIES TO TILLAGE PRACTICES AND SOIL AMENDMENTS IN A TROPICAL ALFISOL

Abstract

Soil amendment with poultry manure and inorganic fertilizer have been reported to increase soil fertility and improve the overall soil heath. However, little is known about the interaction effect of soil amendment and tillage systems on varietal performance of Cowpea (Ife Brown and Sokoto White). This study therefore, investigate the different soil fertility managements and tillage practices on soil physico-chemical and hydraulic properties as well as the growth, varietal yield performance and water use efficiency of Cowpea (Vigna unguiculata (L.) Walp) varieties in tropical Alfisol in Akure Southwestern Nigeria. The experimental design was as a 2 × 2 × 3 factorial combinations comprising of two levels of cowpea varieties (Ife Brown and Sokoto White), two levels of tillage treatments (traditional and no tillage systems) and three levels of soil fertility management measures (poultry manure, inorganic fertilizer and zero fertilizer) to form a total of 12 treatments, replicated 3 times forming a total of 36 plots. The incorporation of poultry manure to the experimental field led to a significant reduction in bulk density and an increase in total porosity under traditional and no tillage treatments compared with NPK fertilizer application and control (zero application of fertilizer and manure) treatments in both varieties. The incorporation of P M significantly (p ≤ 0.001) increased the soil organic matter (SOM) and it follows the order: P M > N PK > Z F among soil amendments under tillage systems and cowpea varieties. In all cases of K, the decreasing order among the various amendment types was P M > N PK fertilizer > Z F (control). There was no significant difference (p > 0.05) between the N PK fertilizer and the Z F (control/unfertilized) treatments in term of soil hydraulic conductivity. However, tillage systems have significant effect (p ≤ 0.001) on K with T T having significantly higher K than N T tillage system. The increase in hydraulic conductivity of T T system is probably due to soil loosening effect from manual and local tillage operations. Highest values in most of the growth parameters were observed in plots treated with NPK fertilizer. Fertilizer and manure application significantly (p≤ 0.05) increased crop yield parameters (number of pods per plant, number of seeds per pod, 100-seed weight, pod yield and seed yield). The increase in yield parameters as a result of soil amendment is due to the increase in soil fertility observed from the application of poultry manure and NPK fertilizer. In both varieties, the FWUE increased with poultry manure and fertilizer applications (P < 0.05) under all treatments. The FWUE of the two varieties was significantly different, and was also significantly influenced by amendment types. Growth, yield, and FWUE of both varieties increased as a result of improved soil physicochemical (nutrient availability) and hydraulic properties, as well as increased water use of cowpea plants due to the application of poultry manure. The study emphasizes the management of soil nutrients through effective soil fertility and tillage management. Improvement in the management of land resource for sustainable agricultural use would be one of the most useful strategies that could help to increase agricultural productivity and address food security.