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Title:	Yield and water use response of winter wheat to winter irrigation in the North China Plain
Author:	L.W. Shao,X.Y. Zhang, H.Y. Sun, S.Y. Chen and Y.M. Wang
PubYear:	2011
Publication Name:	Journal of Soil and Water Conservation
Volume、Issue、Page Number:	66; (2); 104-113
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Abstract:	With intensifying water shortage, adoption of deficit irrigation strategies is likely to increase around the world. Winter wheat (Triticum aestivum L.) is one of the crops that has successfully been grown with deficit irrigation in the North China Plain. However, irrigating once before winter wheat enters dormancy (simplified as winter irrigation [WI]) is still a popular practice in this region. This study investigated the necessity of this irrigation and its effects on crop performance to provide guidelines for better irrigation management. Field experiments at two sites with up to five irrigation treatments (from rainfed up to three irrigations with or without WI) in a randomized block design with four replications were conducted for two to three winter wheat growing seasons from 2006 to 2009 in the North China Plain. Results showed that with good soil moisture at sowing, winter wheat achieved its maximum grain production with two irrigation applications in dry seasons and one irrigation application in wet seasons, both without WI. Winter irrigation increased evapotranspiration by 20 to 25 mm (0.79 to 0.98 in) and increased drainage from the root zone profile by 20 mm during the long winter dormancy period. With good soil moisture conditions at sowing plus some rainfall, soil moisture before winter wheat enters dormancy would be adequate so WI would have little effect on crop growth. Otherwise, the moisture for the top 50 cm (19.69 in) soil profile might become too dry, which would have a negative affect on winter wheat growth at the recovery stage without WI. However, even under dry conditions, WI didn't increase yield of winter wheat with a postdormancy irrigation in early spring. With the same number of irrigation applications, the ones with WI produced lower water-use efficiency (WUE) values than the ones without WI. Under limited irrigation application, irrigation in early spring after winter dormancy produced greater yield and WUE than that with WI. Applying WI encouraged root growth at the topsoil profile, while withholding WI enhanced root length density in the deep soil layer. The results showed that WI increased evapotranspiration and drainage and reduced WUE. Thus, WI should be replaced by early or late spring irrigation after winter dormancy depending on soil moisture conditions.
DOI:	http://dx.doi.org/10.2489/jswc.66.2.104
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