Nitrogen Management in No-Tillage Grain Sorghum Production: I. Rate and Time of Application
- Raj Khosla *a,
- Mark M. Alleyb and
- Paul H. Davisb
Grain sorghum [Sorghum bicolor (L.) Moench] is grown in rotation with wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] in the mid-Atlantic. Sufficient data on N fertilization of sorghum are not available for this region. Our objective was to evaluate the influence of multi-rate N fertilization on dryland sorghum. Treatments consisted of factorial combinations of four starter-band N rates (11, 34, 56, and 78 kg N ha−1) and four sidedress N rates (0, 45, 90, and 134 kg N ha−1). A broadcast treatment of 67 kg N ha−1 at planting was also included. Starter-band was applied 5 cm to the side and below the seed. Sidedress was applied 35 days after emergence at the eight-leaf growth stage. Grain yield ranged from 1.7 to 11.9 Mg ha−1 over eight site-years and was responsive and nonresponsive to N applications on four sites each. Nonresponsiveness was either due to high levels (>85 kg N ha−1) of residual soil mineral N, or severe water stress conditions. Our results indicate that production of sorghum on soils testing high in mineral N (50 kg N ha−1 in the surface 0.3 m) at planting should not receive any starter-band N in conjunction with sidedress N application of 130 kg N ha−1 for optimum economic return to N fertilization. For soils testing low in mineral N, 40 kg N ha−1 starter-band in conjunction with 130 kg N ha−1 sidedress N should optimize the sorghum yields in most situations.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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