Effects of eight tillage treatments on a tropical alfisol: Maize growth and yield

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Abstract
The effects of eight methods of preplanning tillage systems were investigated on maize growth and yield for eight consecutive crops grown from 1980 to 1983 on an Alfisol in south‐west Nigeria. The tillage systems were: (A) no‐till with residue mulch, (B) no‐till with chiselling in the row zone to 50 cm depth, (C) mouldboard ploughing followed by (fb) harrowing, (D) disc ploughing fb rotovation, (E) no‐till without residue mulch, (F) mouldboard ploughing at the end of rains, (G) mouldboard ploughing fb two harrowings with residue mulch (H) mouldboard ploughing fb two harrowings and ridging. In seasons with infrequent rains and long dry spells, seedling emergence was significantly suppressed on ridged plots (treatment H). The 1500 h soil temperature on the ridged seedbed (H) at 5 cm depth exceeded 40°C, and was about 10°C more than in no‐till with mulch (A). The oxygen diffusion rate (ODR) at 10 cm depth was the most in the no‐till mulch and the least in the furrow bottoms. The soil moisture reserve was larger in the no‐till plots than in the ploughed treatments. Plant height and vigour were adversely affected on ridges in seasons with frequent dry spells. In these seasons, maize grain yield declined with the increasing intensity of mechanical tillage. For the eight seasons, the cumulative benefits in grain yield of all the no‐till treatments were 1.76 and 0.32 tonnes ha−1 in comparison with ridges (H) and ploughed (C, D, F, G) treatments, respectively. The mean seasonal yield was 3.37 and 1.00 t ha−1 for the first and second seasons respectively. The seasonal fluctuations in grain yield were related to rainfall amount and the length of growing season.