Yield-rainfall relationships in cereal cropping systems in the Ebro river valley of Spain.

摘要

Studies of 3 farms in the Ebro river valley, Spain, showed that wheat and barley yields were strongly dependent on seasonal rainfall, particularly during November-January and March-May. On the driest farm, in Monegrillo, Zaragoza province (seasonalrainfall 251 mm), yields increased by about 5.9 (wheat) and 9.4 (barley) kg ha-1 for every mm of extra rain during the entire cropping season, taken as October-May inclusive. The other farms, at El Canos and Selvanera in Lleida province, had seasonal rainfalls of 364 and 334 mm, and yields of barley increased by 4.3 and 9.0 kg ha-1, respectively, for each mm of extra rain in the cropping season, taken as September-May inclusive. In Monegrillo, cereals are grown in a cereal-fallow rotation. Normal fallowing (duration 17 months) compared with minimum fallowing (5 months) increased the calculated water content of the top 100 cm of the dominant soils by 19 mm. This extra water was estimated to benefit yield by 7.0% (wheat) and 6.2% (barley), increasing theaverage yields by >300 kg ha-1 to 1222 and 1522 kg ha-1, respectively.