106(4)_str41

 

ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 106, No. 4 (2019), p. 321–328
DOI 10.13080/z-a.2019.106.041

The introduction of soybean in an organic crop rotation in the Nemoral zone: the impact on subsequent spring wheat productivity

Monika TOLEIKIENĖ, Caroline BROPHY, Aušra ARLAUSKIENĖ, Jim RASMUSSEN,
Viktorija GECAITĖ, Žydrė KADŽIULIENĖ

Abstract

The sustainability of an organic crop rotation frequently depends on the residual effects of legume pre-crops. However, the contribution of legumes varies considerably depending on their species as well as local soil and climatic conditions. This research aims to compare the pre-crop effects of traditional grain and forage legumes with those of soybean (Glycine max (L.) Merr.), which is not widespread in Europe latitude 55° due to climatic constrains, on the productivity of subsequent cereals. A three-year (2016–2018) crop rotation was investigated using four pre-crops: spring barley, spring barley intercropped with red clover, pea and soybean. The effect of pre-crops on grain yield and quality and chemical composition of subsequently grown spring wheat was explored. Nitrogen (N) content in grain and straw, mineral nitrogen (Nmin) content in the soil were measured, the carbon to nitrogen (C:N) ratio and net N balance were calculated. The rotation was repeated twice and the results showed that pea and soybean did not produce sufficient biomass and amount of fixed N to maintain a stable positive residual effect in both rotation replications. Under favourable conditions, pea derived 66.1 kg ha-1 N and soybean – 64.7 kg ha-1 N from the atmosphere, while red clover intercropped with spring barley produced 65.4–82.7 kg ha-1 N yearly. Most of the total N (Ntot) accumulated by pea and soybean plants, 69% and 80%, respectively, was removed with grain yield, while comparable percentages of N (59–68%) were left by the residues of red clover and spring barley mixture. As a result, the greatest effect on subsequently grown spring wheat was exerted by the mixture of spring barley and red clover (yield increase 354–1414 kg ha-1). Comparing grain legumes, only efficiently nodulated soybean produced a positive +20.6 kg ha-1 net N balance and increased the yield of spring wheat by 920 kg ha-1. Pea resulted in the negative net N balance and increased the yield of spring wheat by 534 kg ha-1. Mineral nitrogen in the soil increased under all legume pre-crops only in the second year of the crop rotation.

Key words: nitrogen, pea, pre-crop, red clover.

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