Cropping sequence effect of pea and pea management on spring wheat in the northern Great Plains

Annual legumes permit intensified cropping in no-till systems in the drought-prone northern Great Plains. Our objectives were to compare cropping sequence effects of pea (Pisum sativum L.) with fallow, mustard (Sinapis alba L.), and wheat (Triticum aestivum L.), and to measure the effects of pea harvest timing and shoot biomass presence on soil water use and N contribution, and yield and grain quality of subsequent wheat. Pea, mustard, wheat, and fallow preceded spring wheat at three sites in Montana. In the first year, two harvest timings (anthesis and maturity) were included and managed for presence or absence of crop shoot biomass. In the second year, a wheat test crop was grown at four N fertilizer rates. Regardless of management, pea used equal or less soil water, contributed equal or greater soil N, and had equal or greater positive impact on subsequent wheat growth than mustard or wheat. Compared with maturity, midseason harvest timing of pea increased soil N (30-39 kg NO3-N ha(-1)) and soil water (19-39 mm) available in the spring to the subsequent wheat test crop at two of three sites. Under severe drought, midseason harvest of pea increased wheat yield 50% and critically increased grain density compared with the mature pea harvest. At the N-limited site, midseason harvest of pea increased wheat yield 14% and grain protein 9% compared with mature pea harvest. Pea shoot biomass presence did not affect soil water or N, or growth of a subsequent wheat crop.