Applied N and Moisture Level Effects on Yield, Depth of Root Activity, and Nutrient Uptake by Soybeans1
- Bashir Al-Ithawi,
- E. J. Deibert and
- R. A. Olson2
The soybean [Glycine max (L.) Merrill] has commonly been recognized as a rather non-responsive crop to fertilizer treatments compared with cereals, reasons for which are quite obscure. For studying the moisture and nutritional aspects that might be involved in this anomaly, a field experiment was conducted on Sharpsburg silty clay loam, a Typic Argiudoll, at three moisture levels, with three depths of 32P tagged P placement (22.5, 45, 90 cm) during 1974 and 1976. Objectives were to evaluate effects of fertilizer N, residual soil N, and moisture level on yield, zones of root activity, water use efficiency, and the total uptake of N, P, K, Ca, Mg, Fe, Cu, and Zn by the crop.
Seed yield of soybean was increased 675 and 1148 kg/ha by high soil moisture levels compared with low levels in 1974 and 1976, respectively. Total dry matter, percent plant P derived from fertilizer and uptake of all nutrients were also increased with increased soil moisture level. Although placement depth of 32P-tagged P had no effect on total dry matter accumulation and seed yield of soybean there was essentially equivalent utilization of the tagged fertilizer whether placed at 22.5, 45, or 90 cm depth evidencing the deep nutrient extraction capabilities of the soybean plant. Nitrogen fertilizer significantly increased seed yield of soybean at all moisture levels in 1974 but only at low moisture in 1976 with amounts of residual soil NO3-N at planting explaining the difference between the 2 years. Applied N also increased removal of all other soil nutrients measured except Fe. Consumptive water use was greater the higher the rate of N applied and the higher the moisture regime.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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