The effect of reduced tillage of an irrigated silty soil and of a mulch on seedling emergence, growth and yield of maize (Zea mays) harvested for silage

Maize was grown for 1 season as a row-crop on raised beds in a factorial experiment on reduced tillage. The effects of 2 passes of a spring-tined cultivator (Treatment C), of a small 70-mm wide rotary-hoe, ahead of the seeder (Treatment R) and of a mulch (Treatment M) on emergence, growth and yield of maize were determined. Treatment C produced a coarse tilth (41% aggregates > 20-mm diameter; 9% aggregates 0.5–2 mm) in the top 30 mm of pre-irrigated beds of a silty soil. Treatment R produced a fine seed-bed (4% aggregates > 20-mm diameter; 21% aggregates 0.5–2 mm), 70 mm wide and 30 mm deep, along each of the 2 sowing-lines. In the same pass, 2 rows of maize were sown at a depth of 25 mm into the wet soil.

In the mulched treatments (M), where 5 t ha^?1 of barley straw was applied after the crop was sown, to cover the bed, the water content around the seed (0–30-mm depth) over the first 9 days after the crop was sown was 29–74% higher than in the unmulched treatments (M₀). For example, 1 day after the crop was sown, the water content of soil around the seed was 21% in Treatment M, close to field capacity, and 14% in Treatment M₀. In Treatment M, the temperature around the seed (25-mm depth) at 15.00 h over the first 9 days after the crop was sown was almost always significantly lower than in Treatment M₀; for example, the maximum temperatures of Treatments M and M₀ were 32 and 41°C, respectively.

Either Treatment M or R, but not Treatment C hastened emergence of maize seedlings and increased percentage final emergence. There were no significant effects of any treatments on plant yield. However, there was a trend within Treatment M for either Treatments R or C to increase yields.