DRY-MATTER PARTITIONING AND LEAF-AREA OF WINTER-WHEAT GROWN IN A LONG-TERM FALLOW TILLAGE COMPARISONS IN THE US CENTRAL GREAT-PLAINS

Crop management practices (tillage, residue management, fertilization, etc.) define the soil environment to which crops are exposed and thro ugh these environmental conditions control crop growth. The purpose of this paper is to report the response of winter wheat (Triticum aestiv um L.) to long-term (10 years) application of fallow tillage practices (plow, sub-till, and no-till) and N fertilization in terms of above- and below-ground dry-matter partitioning. During 1978, less winter whe at root tissue was produced in the sub-till treatment compared to the average of the plow and no-till treatments. However, in 1979, all trea tments produced the same amount of root tissue. Averaged over all trea tments, root tissue was ca. 7% of the above-ground dry-matter producti on. During 1979, less above-ground dry matter was produced at late gra in fill (27 June) with addition of N fertilizer (929 g m(-2)) than whe n N was not applied (957 g m(-2)). In contrast, during 1980 (at about the same stage of development), application of N resulted in more abov e-ground dry-matter production in the plow and no-till treatments, but addition of N reduced production in the sub-till treatment. Grain yie ld followed similar trends. Nitrogen application also increased tiller production and number of tillers surviving to maturity. Nitrate reduc tase activity was measured to determine if the reported lesser levels of nitrate-N in soils under reduced tillage management changed N metab olism of the plant. Nitrate reductase activity differed among N rates (when measured after N application), but did not differ among tillage treatments. (C) 1998 Published by Elsevier Science B.V. All rights res erved.