Original Articles

Effect of soil tillage, crop rotation and nitrogen application rates on plant-N content of spring wheat (Triticum aestivum L.) in the Swartland wheat-producing area of the Republic of South Africa

Published in: South African Journal of Plant and Soil
Volume 21, issue 4, 2004 , pages: 255–260
DOI: 10.1080/02571862.2004.10635059
Author(s): S.H. MaaliDepartment of Agronomy, Republic of South Africa, G.A. AgenbagDepartment of Agronomy, Republic of South Africa


Studies on nitrogen content in spring wheat were conducted during the 2000 and 2001 growing seasons as part of a long-term tillage and crop rotation trial. Four tillage methods were used, namely conventional tillage (CT), tine tillage (TT), minimum tillage (MT) and no-tillage (NT). Crop rotation systems used were continuous wheat (WW) and wheat/lupine/wheat/canola (WLWC). Three rates of nitrogen fertiliser (60, 100 and 140 kg. N ha-1) were applied as sub-plots. Wheat plants were sampled at tillering stage (S1), stem elongation (S2), flag leaf (S3) (2000 growing season only) and anthesis (S4). In general nitrogen content (% of plant component) decreased as the plant reached maturity. Nitrogen content expressed as g plant-1 and kg ha-1 was affected by tillage method in both growing seasons, but the response depended on the amount of precipitation during the growing season. During the low rainfall year, highest N contents were found in the NT treatment. In contrast to this, CT resulted in the highest N content during high rainfall years. Significant differences in total nitrogen content in the plant (g plant-1) due to crop rotation were observed only at the tillering and flag leaf stages. At both stages, plants from the wheat/lupine/wheat/canola system resulted in significantly higher values than those from the monoculture (wheat/wheat) plots. A non-linear increase in the N content of the wheat crop with an increase in the N-application rate from 60 to 140 kg N ha-1 indicated a decrease in N-use efficiency at higher application rates during both years.

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