Individual study: Trade-offs between winter cover crop production and soil water depletion in the San Joaquin Valley, California
Mitchell J.P., Shrestha A. & Irmak S. (2015) Trade-offs between winter cover crop production and soil water depletion in the San Joaquin Valley, California. Journal of Soil and Water Conservation, 70, 430-440
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Water: Grow cover crops in arable fields
A replicated, randomized, controlled study in 2012–2014 in a mostly rainfed field in the Central Valley, California, USA, found less water in soils with winter cover crops, compared to winter fallows. Water availability: Over the winter, less water was found in soils with cover crops, compared to fallows, in some comparisons (2013: 5.3 cm less water; 2014: 0.67 less; number of comparisons not clearly reported). This was because water was lost from soils with cover crops, but gained in soils with fallows. Methods: There were three plots for each of three cover crops (legumes: 45% Vicia faba, 35% Pisum sativum, and 20% V. sativa; legumes and triticale: 40% P. sativum, 30% V. sativa, and 30% Tritocosecale; or brassica: 45% Brassica juncea, 40% Sinapsis alba, and 15% Raphanus sativus) and there were three fallow plots (kept bare with herbicide). Each plot was 10 x 30 m. All plots were irrigated only to establish the cover crop (10 cm/year). Plots with cover crops were fertilized (112 kg N/ha) and seeds were sown in November. Water content was measured twice/week in January–March (0–90 cm depth).