Tillage effects on water use and grain yield of winter wheat and green pea in rotation

Under water-limited conditions, increasing water use efficiency (WUE) is essential for successful crop production. A 7-yr study (1977-1982, and 1985) to evaluate tillage and tillage timing effects on sod water storage, crop water use, and grain yield of winter wheat (Triticum aestivum L.) and spring green pea (Pisum sativum L.) in rotation, was conducted near Pendleton, OR. Treatments included (i) fall plow (FP)-fall moldboard plow after wheat and after pea, (ii) maximum tillage (MT)-fall roto-till after wheat and fall sweep after pea, (iii) spring plow (SP)-spring moldboard plow after wheat and fall moldboard plow after pea, and (iv) minimum tillage(MinT)-no-till (NT) after wheat and fall sweep after pea. During the wheat phase, water storage efficiency was 44, 40, 38, and 34%, for FR MT, SP, and MinT, respectively. Corresponding values during the pea phase were 50, 53, 59, and 57%, for FR MT, SR and MinT, respectively. Wheat used all of the stored water and an additional 31, 41, 43, and 61% more water than water stored under FP, MT, SP and MinT, respectively. Pea used 71, 67, 67, and 60% of stored water under FP, MT, SP and MinT, respectively. Wheat and pea yields under MT, FP, and SP were not different. Lowest yield was obtained under MinT during both wheat and pea phases. WUE was highly correlated with yield and was lowest under MinT. Improving weed control, retaining stubble for sod erosion control, and reducing sweep operations in MinT should improve yields in this treatment.