N-utilization in non-inversion tillage systems

Abstract

When changing from ploughing to non-inversion tillage, N rates are of particular importance both for farmers and the environment. A tillage and fertilizer experiment was established in Denmark under temperate coastal climatic conditions to evaluate the N fertilizer responses on yields and N uptake of six crops in different crop rotations, three winter wheat crops ( Triticum aestivum L.), one winter barley ( Hordeum vulgare L.), one winter oilseed rape ( Brassica napus L.) and one spring barley crop during the years 2003–2005. The experiment was established in autumn 2002 on a loamy sand with 92 g clay kg −1. The tillage treatments were stubble cultivating to 8–10 cm or 3–4 cm, direct drilling, or ploughing to 20 cm. Five different fertilizer N treatments were included: 1:50% (0.50N), 2:75% (0.75N), 3:100% (1.00N), 4:125% (1.25N) of recommended N rates, respectively, and 5: application of 15–30 kg N ha −1 of the total fertilizer N amount in autumn to autumn-sown crops (1.00N Aut). In all the crop rotations, straw was chopped and retained after harvest. Different types of N fertilizer responses were observed in the six crops, but generally yields were lower with non-inversion tillage than with ploughing. On two occasions, yields in ploughed plots were significantly ( p < 0.05) higher than yields with direct drilling as an average of N treatments. Increasing the fertilizer application was generally not able to offset the growth reduction, which resulted from poor growth in patches probably caused by soil compaction in plots with non-inversion tillage. Applying some of the N allocation in autumn cannot be recommended for stimulation of growth of winter cereals or winter oilseed rape with either non-inversion tillage or ploughing.