The effect of nitrogen top-dressing at first node on wheat yield and quality
1999
Lowe, D.
The majority of wheat varieties grown in Zimbabwe are soft, white spring wheats, which do not consistently achieve a grain protein content of 12.5percent, preferred by -the millers. Zimbabwe now has a grading system where premiums are being paid for grain protein. One way of improving grain protein in wheat is through the timing of nitrogen top-dressing. On receiving reports from CIMMYT on the benefits of applying most of the nitrogen at first node, a series of ten trials was conducted in 1997. All trials included two times of nitrogen top-dressing (21 days after planting and first node), and five rates of nitrogen (80 -240 kg/ha). Series A consisted of four trials at three sites (ART farm, Macheke and Mid Save) and followed soybeans, tobacco and cotton, respectively. At ART farm there were two trials under zero and under conventional tillage. Series B consisted of six trials at three sites (Mutepatepa, Sebakwe and Shamva) on adjacent lands following maize and soybeans. These trials included two tillage treatments (zero and conventional tillage). Timing of nitrogen top-dressing did not affect yield in any of the trials, but the first node application improved grain protein in three of the trials. The biggest improvement in grain protein was after cotton (Mid Save). The other improvements in grain protein were after maize (Shamva) and after soybean (ART, conventional till). Nitrogen trials in 1995 and 1996 concentrated on applying 30-35 kg/ha N at anthesis, with no positive results. Results from the first node application in 1997 were encouraging and further work is being conducted in 1998. Results also showed a benefit in yield and protein by growing wheat after soybean as opposed to maize and more trials are in progress in 1998.
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