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 through these environmental conditions control crop growth. The purpose of this paper is to report the response of winter wheat (Triticum aestivum L.) to long-term (10 years) application of fallow tillage practices (plow, sub-till, and no-till) and N fertilization in terms of aboveand below-ground dry-matter partitioning. During 1978, less winter wheat root tissue was produced in the sub-till treatment compared to the average of the plow and no-till treatments. However, in 1979, all treatments produced the same amount of root tissue. Averaged over all treatments, root tissue was ca. 7% of the above-ground dry-matter production. During 1979, less above-ground dry matter was produced at late grain fill (27 June) with addition of N fertilizer (929 g mp2) than when 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 above-ground dry-matter production in the plow and no-till treatments, but addition of N reduced production in the sub-till treatment. Grain yield followed similar trends. Nitrogen application also increased tiller production and number of tillers surviving to maturity. Nitrate reductase activity was measured to determine if the reported lesser levels of nitrate-N in soils under reduced tillage management changed N metabolism of the plant. Nitrate reductase activity differed among N rates (when measured after N application), but did not differ among tillage treatments.