Soybean Response to Potassium Fertility under Four Tillage Systems
1988
Vasilas, B. L. | Esgar, R. W. | Walker, W. M. | Beck, R. H. | Mainz, M. J.
Because tillage affects root growth and activity, it affects the ability of plants to utilize soil and fertilizer nutrients. It has not been determined if K fertility recommendations developed for clean tillage systems are appropriate for reduced tillage systems. Therefore, an experiment was conducted on a Muscatine silt loam (fine-silty, mixed, mesic Typic Haplaquoll) and a Sable silty clay loam (fine-silty, mixed mesic Aquic Argiudoll) to determine the response of soybean [Glycine max (L.) Merr.] cultivars Williams 82 and Century to three levels of soil K fertility under four tillage systems over 2 yr. The tillage systems were moldboard plow (fall plowed plus spring disk), chisel plow (fall chisel plowed plus spring disk), spring disk, and no-till. Soil K treatments were 336 kg exchangeable K ha−¹, 336 kg exchangeable K ha−¹ plus 73 kg banded K ha−¹, and 560 kg exchangeable K ha−¹. A corn (Zea mays)-soybean rotation was used. Grain yields were similar for the moldboard plow, chisel plow, and disk systems. Grain yields were consistently lower for the no-till system. This response was greatest for the cultivar Century in a year when herbicide carryover and Phytophthora (Phytophthora megasperma) damage under no-till reduced final plant populations by 44% compared to that with the moldboard plow system. Increasing the exchangeable soil K level from 336 to 560 kg ha−¹ increased grain yields of Century during a dry growing season. Tillage did not affect the magnitude of response, and banded K had no effect on grain yield. We concluded that the tillage system should not influence K fertility recommendations for soils such as these. Contribution of the Dep. of Agronomy and the Agric. Exp. Stn., Univ. of Illinois
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