Water Use Efficiency of Rainfed and Irrigated Bread Wheat in a Mediterranean Environment

Abstract

Supplemental irrigation (SI) is defined as the application of a limited amount of water to rainfed crops when In West Asia and North Africa, shortage of water limits wheat precipitation fails to provide the essential moisture for (Triticum aestivum L.) production. Current irrigation practices aim at maximizing grain yield, but achieve lower return for the water normal plant growth. This practice has shown potential consumed. Maximizing water use efficiency (WUE) may be more in alleviating the adverse effects of unfavorable rain suitable in areas where water, not land, is the most limiting factor. patterns and thus improving and stabilizing crop yieldsWe examined the effects of various levels of supplemental irrigation (Perrier and Salkini, 1991;Oweis et al., 1998; Zhang (SI) (rainfed, 1/3 SI, 2/3 SI, full SI), N (0, 5, 10, 15 g N m Ϫ2 ), and and Oweis, 1999). Early studies at ICARDA showed sowing time (Nov., Dec., Jan.) on evapotranspiration (ET) and WUE that applying two or three irrigations (80-200 mm) to of wheat. WUE was calculated for rain (WUE r ), for total water (gross:wheat increased crop grain yield by 36 to 450%, and rain ϩ irrigation) (WUE g ), and for SI water only (WUE SI ). ET ranged produced similar or even higher grain yields than in fully from 246 to 328 mm for rainfed crops, with grain yield ranging from irrigated conditions (Perrier and Salkini, 1991; Oweis, 130 to 270 g m Ϫ2 and total dry matter from 380 to 1370 g m Ϫ2 . Irrigated 1994). Supplemental irrigation is widely practiced in crops had ET of 304 to 485 mm, with grain yield of 170 to 500 g m Ϫ2 . The degree to which water supply limits grain yield was indicated by Syria, and in southern and eastern Mediterranean counthe ratio of pre-to post-anthesis ET (2.1-2.4:1). The SI treatments tries. However, excessive use of water in SI because of significantly increased WUE g : from 0.77 to 0.83 to 0.92 kg m Ϫ3 in low irrigation cost and attractive gains from increased November and December sowings for 1/3 SI and from 0.77 to 0.92 yields has resulted in a decline of aquifers and deteriorakg m Ϫ3 in November sowing for 2/3 SI. The highest WUE g and WUE SItion of water quality in many areas (Ward and Smith, were achieved at 1/3 to 2/3 SI. WUE was substantially improved by 1994).applying 5 and 10 g N m Ϫ2 , with little increase for higher rates. DelayingIncreasing the portion of water used for plant transpisowing had a negative effect on WUE for both irrigation and rainfed ration through a large and early canopy can increase conditions. In this rainfed Mediterranean environment, WUE can be WUE. In Mediterranean environments, where crop cansubstantially improved by adopting deficit SI to satisfy up to 2/3 of opy development in winter is slow and rain occurs as irrigation requirements, along with early sowing and appropriate levels of N.

Optimizing Wheat Water Productivity as Affected by Irrigation and Fertilizer-nitrogen Regimes in an Arid Environment

“…The highest WP I , 2.15 kg m -3 , was achieved under deficit irrigation (W1) and N2 strategies in 2002-03, indicating that the irrigation water and nitrogen were most efficiency used in this treatment. Similar results were reported by earlier researchers working with deficit irrigation of wheat and other crops (Oweis et al, 2000;Zhang et al, 2004;Ali et al 2007). The lowest WP I , 0.79 kg m -3 , was obtained under the greatest irrigation amount (W4) and lowest N1 strategy in 2007-08.…”

Impact of Sowing Date on Yield and Water Use Efficiency of Wheat Analyzed through Spatial Modeling and FORMOSAT-2 Images

“…; Figure 12) appeared consistent with values derived from previous experiments on wheat crops, both in Mediterranean and in temperate climates [87,88]. Water use efficiency experienced a high variability, which is mainly explained by sowing practices: the determination coefficient between the day of plant emergence and the water use efficiency is 0.59.…”

Supplemental irrigation potential and impact on downstream flow of Karkheh River basin in Iran

“…The goal of supplemental irrigation is not to maximise yield per unit area but to optimise water productivity (benefit per unit water). Results of research experiments have shown substantial increases in crop yields and water productivity in response to the application of relatively small amounts of supplemental irrigation (Ghahraman and Spaskhah, 1997;Oweis et al, 1998Oweis et al, , 2000Fox and Rockström, 2003;Tavakoli and Oweis, 2004;Oweis and Hachum, 2006). At the farm level, supplemental irrigation increases yields, water productivity, and stability of crop production under different climatic conditions.…”