STATUS OF AVAILABLE MICRONUTRIENTS OF THE BASEMENT COMPLEX ROCK – DERIVED ALFISOLS IN NORTHERN NIGERIA SAVANNA.

The contents of available boron, zinc, copper, iron and manganese were determined in twenty surface soils (0-30cm depth) and profile pits collected from Northern Guinea and Sudan savanna zones which are the major tomato and horticultural crops growing areas of northern Nigeria savanna. The contents of available B from surface soils, extracted with hot water, varied from 0.04 – 0.28 with a mean of 0.14 mg kg-1, while Zn, Cu, Fe  and Mn, extracted with 0.1N HCl, varied from 1.8 –10.5, 1.0 –  9.0, 2.5 –75 and 2.8 – 18 mg kg-1, with  means of 4.2, 2.9, 19.6 and 9.2 mg kg-1 respectively. The contents of B, Zn, Cu, Fe and Mn in the profile pits ranged from 0.08 – 0.18, 1.5 – 3.5, 0.9 – 3.3, 14 – 26.2 and 11.2 – 20.5 mg kg-1 with means of 0.12, 2.4, 1.9, 20.7 and 15.0mg kg-1 respectively. Boron is deficient in all the soils; Zn is deficient in only some of the soils, while the contents of the other micronutrients are adequate. The micronutrients are significantly related to some of the soil properties tested, Soil clay correlated (P=0.01) positively with Cu, Zn, Mn and Fe (r= 0.476**, 0.404**, 0.407** and 0.469** respectively). Similarly, organic C correlated positively with Fe, Cu and Mn.  Also, there are significant relationships among the micronutrients; Fe correlated with all the other micronutrients – Cu, Zn, Mn (P=0.01) and B (P=0.05).  While Zn correlated with Fe, Cu and Mn. For soils of the pedons, sand and silt correlated with Zn and Cu, pH (H2O) correlated with Fe, while pH (CaCl2) correlated with B and Fe. Among the micronutrients, B and Cu correlated with Zn. There would be need for B and Zn application to the soils for successful and profitable crop production

Yield and Nuse efficiency of five tropical maize genotypes under different N levels in the moist savanna of Nigeria

Two field experiments were conducted during the 1993 and 1994 growing seasons at Samaru (7° 38' E; 11° 11' N), northern Nigeria, to evaluate N-use efficiency (kg grain per kg available soil N) and yield of 5 maize genotypes planted early in the season under five levels of N. The hybrid (8644-27) gave the highest grain yield and was the most N-use efficient genotype. It had a longer grain filling period, a higher harvest index, and a greater 1000-kerneI weight than other genotypes. The most widely grown open pollinated variety (TZB-SR) was the least efficient in utilizing available soil N for grain production, although it had the highest number of kernels per ear and total above-ground dry matter. The semiprolific (SPL) and EV8728-SR genotypes appeared to have a higher potential to adapt to nitrogen stress than other genotypes. They had higher grain yields under zero-N in both years, but the differences were not significant. They also showed greater synchronization of anthesis and silking, which indicates better ability to tolerate nitrogen stress. Traits such as extended grain filling and 1000-kernel weight should be further investigated for inclusion in a breeding scheme to increase maize yield. Early planting to capture the N flush, and application of a suboptimal amount of N (60 kg/ha at 2 WAP) was adequate for production of all the genotypes under the loamy soil conditions of the chosen site. A combination of legume rotation, 60 kg N/ha, and an N-use efficient genotype (8644-27) gave a yield advantage of 1.3 t/ha over a monocrop maize supplied with 60 kg N/ha on farmers' fields in the moist savanna of Nigeria