Growth and nutrient concentration of grain sorghum as affected by rates of injected amendments in an acid subsoil

Abstract

A greenhouse study was conducted to determine the effects of different rates of calcium nitrate, calcium phosphate, ammonium phosphate, and dolomitic limestone on grain sorghum [Sorghum bicolor (L.) Moench] shoot growth, tissue concentration, and total contents in a compacted layer of acid subsoil (pH 4.3) subject to a slit‐till treatment. Cylinders were prepared by layering A and B horizons of a Marvyn loamy sand soil (fine‐loamy, siliceous, thermic, Typic Hapludult) to form 56 cm of subsoil and 10 cm of topsoil in polyvinylchloride (PVC) tubing (20 x 66 cm). A 6‐cm‐thick artificially prepared hardpan with a bulk density of 1.76 Mg m^‐3 was created at the top of the subsoil layer. The amendments, 500 μg/g limestone and 15 μg/g for the other amendments, were injected into a 10 x 10 x 0.4‐cm slit. To obtain different concentrations of injected amendments, the amount injected was increased two‐ and threefold. Sorghum shoots were harvested 35 days after emergence and plants allowed to tiller. Shoot dry weight was increased by calcium nitrate and ammonium phosphate amendments, but the dolomitic lime slurry reduced shoot dry weight below the check. Rate of injection did not have any influence on dry weight. Shoot P and Mg concentration was increased by rate of injection while amendments increased K, Mg, and Ca concentration. The total content of shoot followed a similar trend as concentration, but K content was increased at the 2x rate with calcium nitrate.

Key words:

• Soil pH
• exchangeable ions
• slit tillage
• root growth
• tillage pan
• hardpan

Notes

Cooperative research of USDA‐ARS, Soil‐PIant Interaction research unit and Department of Agronomy and Soil, Auburn University.

Soil Scientist, U.S. Department of Agriculture Agricultural Research Service, Soil‐Plant Interaction Research Unit, and Assistant Professor, Department of Agronomy and Soils, Auburn University, AL 36849.