Productivity and N-fixation of legume-cereal intercrops and their monocrop counterparts in organic cropping systems
In recent years, western Canada has seen considerable growth in organic production. This is due to heightened environmental awareness, reduced input costs, diversification of market opportunities, and food safety aspects. On the prairies, organic production generally includes the use of annual green manure (GrM) crops, which are plowed under to add nutrients to the soil. However, in a GrM plow-down year, farmers face loss of income. One alternative to growing a traditional GrM could be growing legumes alone or intercropping them with cereals and managing them as green feed forage (GF) for use on-farm or for sale to local livestock producers without compromising soil fertility levels. Intercropping legumes with cereals may be a novel approach to problems of nitrogen (N) supply as the legume may provide N to the current and subsequent crops. It was hypothesized that by intercropping the legume with a cereal, the inorganic N supply would be reduced to levels where N fixation in the legume would be stimulated. This study (i) compared yield in monoculture legume with legume-cereal intercrops (ii) investigated whether increasing cereal density stimulated the legume to fix more N (iii) Compared yield of a cereal grown after the GrM and GF crop treatments. The study included mixtures of feed pea (Pisum sativum cv 40-10 silage pea), oat (Avena sativa L.cv AC Morgan), and triticale (X Triticosecale Wittmack cv Pika). The experiment consisted of 16 treatments and 4 replicates in which feed pea, oat, and triticale were grown alone or in combination and managed as GrM or GF. Wheat and fallow (tillage) served as cropped and uncropped controls respectively. The intercropped oat was seeded at three densities (50, 100, and 150 plants m-2). In the second year, wheat was seeded in all plots. In this paper, biomass, total nitrogen (N), and nitrogen derived from the atmosphere (Ndfa) of treatments and subsequent yields of wheat grown after the treatments at the Delisle site are discussed. Results show that the oat (4238 kg ha-1) and fieldpea + oat 2 (3630 kg ha-1) treatments had the highest biomass whereas the triticale (1357 kg ha-1) treatment had the lowest. Among the intercrops, only the fieldpea + oat 2 treatments had higher total nitrogen (91.61 kg ha-1) than their monocultures, with the oat treatment being the least (45 kg ha-1). The highest %Ndfa was achieved at the highest intercropped cereal density of fieldpea + oat 1 (84%). Wheat grain yield were consistently higher following GrM treatments whereas biomass removal significantly compromised subsequent wheat yields in the GF treatments.
green feed forage
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