Response of irrigated fodder oats to nitrogen fertilization as influenced by tillage

Irrigated green forage production under reduced tillage is thwarted by the failure to obtain adequate N fertilization. Forage accumulation, yield and nitrogen response in relation to tillage and N application were studied for two years during 1980–1982. Forage accumulation, plant height and final forage yield were significantly affected under minimum tillage (T₁). However, plant growth and green and dry forage yields were comparable under reduced (T₂) and conventional (T₃) tillage. Reduction in yield under T₁ was associated with restricted root growth and high soil strength and bulk density in the surface and subsurface layers. The optimum dose of N for T₁, T₂ and T₃ was calculated to be 107, 120 and 113 kg N ha^?1 and the estimated dry matter yield for these rates of N under each of the three tillage systems was 6.6, 9.1 and 9.5 t ha^?1, respectively. The interaction between different tillage systems and N application rates for green and dry matter production was not significant.