부산대학교 도서관

Few studies report long‐term effects of various tillage and crop rotation practices. Studies were conducted to compare the relative ability of various tillage and crop rotation combinations (3 ✕ 3 factorial) to sustain corn (Zea maysL.), soybean (Glycine maxL.), and oat (Avena sativaL.) yields. The tillage and rotation combinations were continuously applied for more than 20 years to a well‐drained Wooster silt loam (fine‐loamy, mixed, mesic Typic Fragiudalf), an imperfectly drained Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf), and a very poorly drained Hoytville silty clay loam (fine, illitic, mesic Mollic Ochraqualf). Tillage treatments were no‐tillage; plow and then plant; and plow, disk, and plant. Rotation treatments on the Wooster and Hoytville soils included continuous corn, corn and soybean in a 2‐year rotation, and corn‐oats‐meadow in a 3‐year rotation. Only continuous corn was grown on the Crosby soil. Corn yields were always positively influenced by no‐tillage on the Wooster soil and negatively influenced on the Hoytville soil. The results obtained for the Crosby soil were mixed. The average yearly corn yield increase and decrease due to no‐tillage on the Wooster and the Hoytville soils were 1070 kg ha−1and 503 kg ha−1, respectively. The negative response to no‐tillage on the Hoytville soil was primarily due to the large decrease in yield obtained as a result of the continuous corn rotation treatment (average annual yield decrease, 880 kg ha−1). Yield responses of soybean and oats on the Wooster and the Hoytville soils were similar to those observed for corn. When Phytophthoraroot rot resistant (tolerant) soybean cultivars were grown on the Hoytville soil with the standard cultivars which had been used during most of the experimental period, yield differences between the no‐tillage and plow treatments were essentially eliminated. This study suggests that yield reductions of corn and soybean associated with no‐tillage on heavy clay, very poorly drained soils may be reduced by rotating crops and/or by the use of disease resistant cultivars.