Resumen

FERNANDEZ, Romina; QUIROGA, Alberto  y  NOELLEMEYER, Elke. Cover crops: a viable alternative for the semiarid Pampa region?. Cienc. suelo [online]. 2012, vol.30, n.2, pp.137-150. ISSN 1850-2067.

The effect of cover crops (CC) on the provision of soil cover, N sequestration, accumulation of available water and the yield of a subsequent summer crop was evaluated. A field experiment with the following treatments was established: fallow without cover crop (B) and rye as CC, control (CT), and fertilized (CF) in a randomized complete block design with plots divided in two moments of drying of CC: July (CTJ and CFJ respectively) and August (CTA and CFA respectively). On all treatments, two summer crops (CV), corn and sorghum were planted after fallowing at the end of November. Soil moisture and nitrate-N were determined at seeding of the CC, during their growing season, and at planting and flowering of corn and sorghum. Consumptive water use (UC) and water use efficiency (EUA) of CC, corn and sorghum were calculated. The standing biomass of CC was determined at the two dates of drying (J and A), and at planting of the summer crops and during their growing period the CC biomass litter was measured. The carbon (C), nitrogen (N) and phosphorus (P) contents of the dry matter were determined for all sampling dates. At planting of the summer crops, B treatment had less available water stored in the soil than CC, and J stored more water than A treatment. Total dry matter production of CC was higher in F and when dried in A. The CC sequestered important amounts of C, N and P, preventing potential leaching losses of N during the fallow, and CC litter contributed considerable amounts of both nutrients to the subsequent summer crops. Corn yields were related to water availability as conditioned by CC, and were therefore higher in CC than in B treatments (4044 and 1015 kg ha-1 respectively). Sorghum yield was not affected by previous soil management with or without CC, due to the longer phenological cycle of this crop which enabled it to make use of more rainfall specifically between planting and flowering.

Palabras clave : Fallow; Rye; Water use efficiency; N and P sequestration; Corn and sorghum yields.

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