Legume Green Fallow Effect on Soil Water Content at Wheat Planting and Wheat Yield

Abstract

Growing a legume cover crop in place of fallow in a winter wheat (Triticum aestivum L.)–fallow system can provide protection against erosion while adding N to the soil. However, water use by legumes may reduce subsequent wheat yield. This study was conducted to quantify the effect of varying legume termination dates on available soil water content at wheat planting and subsequent wheat yield in the central Great Plains. Four legumes [Austrian winter pea, Pisum sativum L. subsp. sativum var. arvense (L.) Poir.; spring field pea, P. sativum L.; black lentil, Lens culinaris Medikus; hairy vetch, Vicia villosa Roth.) were grown at Akron, CO, as spring crops from 1994 to 1999. Legumes were planted in early April and terminated at 2‐wk intervals (four termination dates), generally starting in early June. Wheat was planted in September in the terminated legume plots, and yields were compared with wheat yields from conventional till wheat–fallow. Generally there were no significant differences in available soil water at wheat planting due to legume type. Soil water at wheat planting was reduced by 55 mm when legumes were terminated early and by 104 mm when legumes were terminated late, compared with soil water in fallowed plots that were conventionally tilled. Average wheat yield was linearly correlated with average available soil water at wheat planting, with the relationship varying from year to year depending on evaporative demand and precipitation in April, May, and June. The cost in water use by legumes and subsequent decrease in wheat yield may be too great to justify use of legumes as fallow cover crops in wheat–fallow systems in semiarid environments.

Management of crop water under drought: a review

“…They avoid nutrient losses and soil erosion, provide additional organic input to the soil and improve its physical, chemical and biological quality (MacRae and Mehuys 1985;Meyer et al 1999;Schutter and Dick 2002;Vidal and López 2005;Liu et al 2005). Introduction of an additional crop, however, was considered to reduce water storage compared to an otherwise bare soil, resulting in higher depletion at planting of the subsequent main crop (Mitchell et al 1999;Nielsen and Vigil 2005;Islam et al 2006). On the contrary, Bodner et al (2007) reported only low differences in evapotranspiration between a cover cropped and a bare soil under semi-arid, supply-driven conditions in East Austria.…”

“…These different findings are mainly related to the duration and climatic conditions during cover crop growth. Those studies reporting significant soil water depletion were conducted in locations with higher temperature during cover crop growth (Central Great Plains; Nielsen and Vigil 2005) and/or predominant winter rainfalls (California; Mitchell et al 1999;Islam et al 2006). On the contrary, in the semi-arid continental climates of Central and Eastern Europe, the main growing period of cover crops is autumn until crops are terminated by frost before winter.…”

Productivity and residual benefits of grain legumes to sorghum under semi-arid conditions in southwestern Zimbabwe

“…Nielsen and Vigil (2005) indicated that soil moisture was an important factor in determining the residual benefits to cereals grown in rotation with green manure legumes in North America. Short duration, determinate legumes may result in more residual soil water for subsequent crops whereas long duration and/or indeterminate legumes may remove more water than cereal crops.…”

Choice of Summer Fallow Replacement Crops Impacts Subsequent Winter Wheat

“…Wheat yield in the wheat-corn-millet system averaged 52% (1530 kg ha 21 ) less than in the wheatcorn-fallow system. Wheat yield has been reported to be strongly correlated with available soil water at wheat planting (Nielsen et al, 1999;Nielsen et al, 2002;Nielsen and Vigil, 2005), with the response ranging from 39.7 to 282.9 kg ha 21 cm…”