Evaluation of the Green Manure Potential of Austrian Winter Peas in Northern Idaho
- R. L. Mahler and
- D. L. Auld
The objective of this field study was to determine the effect of Austrian winter peas [Pisum sativum spp. arvense (L.) Poir] used as either a green manure (GMP) or seed pea (SP) crop on soil N levels, and yields of subsequent crops of winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.). The Austrian winter pea-winter wheat-spring barley (GMP-WW-SB) rotation was compared with seed pea-winter wheat-spring barley (SP-WW-SB), spring barley-winter wheat-spring barley (SB-WW-SP), and summer fallow-winter wheat-spring barley (SF-WW-SB) cropping sequences at two sites similar in annual precipitation. After harvest of the initial rotational crop, plots were divided into four subplots and four rates of N were applied as a topdress application following planting of ‘Stephens’ winter wheat. Spring barley was planted the third year. Winter wheat yields, spring barley yields, and inorganic soil N were not significantly affected by rotation ✕ N fertilizer interactions. Winter wheat yield averages following GMP, SP, SF, and SB were 6.6, 6.4, 6.3, and 4.7 Mg ha−1, respectively. Average N feitilizer equivalent values of 94, 75, and 68 kg ha−1 were provided by GMP, SP, and SF, respectively, to the following winter wheat crop. Yield differences resulting from crop rotation or N fertilization rate were not observed in the third year of the cropping sequence. Austrian winter peas used as either a GMP or SP crop provided more inorganic N for the following winter wheat crop than SF or SB. From a 3-yr total yield the SP-WW-SB was the most efficient cropping sequence, as cereal yields were comparable to the GMP-WW-SB and SF-WW-SB rotations; however, since SP was harvested three crops instead of two (other rotations) were produced.
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