Saturday, 15 July 2006
152-8

Influence of Tillage, Crop Rotation and Phosphorus Fertility on Grain Sorghum Yields.

John E. Matocha1, M. Richardson2, and Steve Livingston1. (1) Texas A&M Agricultural Research and Extension Center, 10345 Agnes, Corpus Christi, TX 78406-1412, (2) Texas Agricultural Experiment Station - Corpus Christi, 10345 Agnes, Corpus Christi, TX 78406

Abstract

Rapidly rising production input costs for grain sorghum [sorghum bicolor (L.) Moench] challenge the producer to utilize or adapt alternate production methods to improve profitability. Reduction in energy and labor input costs through reduced tillage and potentially yield enhancing crop rotations with improved nutrient use may be the alternative methods for producer consideration. Objectives of this research include investigations of fossil fuel saving tillage practices, possible yield enhancing crop rotations and varying levels of fertilizer phosphorus (P) and micronutrients, iron (Fe) and zinc (Zn), on grain sorghum production. The experimental site was a Clareville clay loam (hyperthermic, Pachic Argiustoll) located west of Robstown, TX (southern Texas). Conventional tillage (CT, 7-8 tillage trips; 6-10" tillage depth) was compared with minimum tillage (MT, 3-4 trips; 3" maximum depth) under both continuous sorghum cropping and a sorghum: cotton (Gossypium hirsutum L.) yearly rotation. The major blocks, cropping systems, and sub-blocks, tillage systems were evaluated at three P fertilization rates in split-plots. Micronutrients, Fe and Zn, were included at the high P rate in the minimum tilled (MT) treatment. Initial year results for sorghum following cotton compared to sorghum following sorghum showed a significant 30 percent grain yield increase when averaged across all tillage and fertilizer variables. With severe moisture stress in years 2 and 3, the rotation benefit decreased substantially due to drought stress. Phosphorus, Zn and Fe fertilizer responses were measured in the third year. Early season plant growth differences in favor of MT failed to translated into final grain yield differences due to moisture stress prior to physiological maturity. Grain yields in Year 4 were considerably improved over yields for the previous two years. While overall average yields were not significantly affected by treatment, yield breakout within tillage system shows up to 22% yield gain directly attributed to rotation with cotton. Yield response to P approached 28% under MT with sorghum following cotton with a lesser response in continuous sorghum. Economic evaluation of the positive benefits of reduced tillage, crop rotations and P indicate considerable impact by these variables. Summary of differences in input costs for power unit, equipment and labor allocation for sorghum production using the MT system in contrast to CT showed savings of approximately $90.00 per hectare. The 4-year average yield increase due to rotation was an impressive 21 percent. Assuming this yield increase translates into at least 588 kg\grain\ha or some $37-$40 per hectare additional net income, the additive benefits of using the MT system and crop rotation practices exceed $124.00 per hectare.


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