EFFECT OF LIME RATES ON NUTRIENT AVAILABILTY, MOBILITY, AND UPTAKE DURING THE SOYBEAN-GROWING SEASON

Abstract

Soil acidity, associated with elemental deficiencies and toxicities, is a limiting factor in southern agriculture. It is related to the predominance of highly weathered and leached clayey and coarse-textured soils. Liming is an essential practice, and research has been done to elucidate the relationships among liming, soil acidity, and plant growth. However, there is a need to continue to quantify the impact of liming on reducing toxic levels of Al and Mn, on increasing nutrient availability and mobility, and on nutrient uptake during the growing season by determinate soybean varieties. The main objective of this study was to determine the effect of lime levels and time on nutrient availability, mobility, and uptake during the entire soybean growing season, under field conditions. Liming with the recommended rate of 3000 kg/ha was sufficient for optimum soybean yields and seed composition. It also increased soil pH from 5.1 to 5.9 within 4 wk, decreased the exchangeable Al from 29 to 3 ppm within 6 wk, reduced the extractable Mn from 23 to 15 ppm within 6 wk, and increased the extractable P from 3 to 51 ppm within 4 wk. Shoot Al concentrations decreased after week 4 with the onset of exponential growth, despite increasing accumulation rates. Total shoot Al increased after week 4 with plant growth and in spite of decreasing Al concentrations. The daily Al accumulation rate in the shoots increased from week 4 to week 12 in association with fast plant growth and available B horizon Al, despite decreasing Al in the A horizon. The Al accumulation rate decreased to-ward the end of the growing season in association with slow plant growth and loss of roots and root activity. Similar results were observed for Mn and P.