Semester of Graduation

spring 2023

Degree

Master in Agricultural Management (MAM)

Department

School of Plant, Environmental, and Soil Sciences

Document Type

Thesis

Abstract

Sulfur (S) is a structural component of amino acids such as cysteine and methionine and is involved in important functions within the plant like photosynthesis, carbon and nitrogen metabolism, protein synthesis of oils, and detoxification mechanisms. Sulfur deficiency in crops has intensified around the world. Some of the reasons are improvement in controlling SO2 emissions from industries, growing usage of high analysis S-free fertilizers and augmented cropping intensity. Sulfur fertilization has become an important factor in crop production systems and fertilization guidelines for S need to be up-to-date to improve use efficiency and compensate for rising prices of fertilizers. This study was conducted in 2019 and 2020 at two locations at the LSU AgCenter Central Research Station in Baton Rouge, LA to: (1) evaluate the potential of elemental- and sulfate-based S sources, and (2) establish the optimal S application rate to maximize production in a soybean-corn rotation system in Louisiana. A 3 (sources: calcium sulfate (CaSO4), ammonium thiosulfate (ATS) ((NH4)2S2O3), and 50% calcium sulfate + 50% elemental S) x 4 (rates: 0, 23, 45, and 90 kg ha-1) factorial treatment structure was arranged in a randomized complete block design with four replications. Grain yield, soil S at midseason and harvest, leaf and grain S, and S removal rate were measured. Source had a significant effect on soybean yield in 2019 with thiosulfate obtaining the highest yield. Sulfur source had a significant effect on soybean seed S removal rate with thiosulfate obtaining the highest average S removal. Rates had no effect on yield of corn and soybean for both years but increased corn grain S content and removal rate. An estimate of optimal S rate using Cate-Nelson method showed that yield tended to decline with application rate below 23 kg S ha-1 and maximize at an application rate not exceeding 45 kg S ha-1. The estimated critical soil S was 40 and 52 mg kg-1 based on fitted linear plateau model using leaf S and grain/seed S removal rate as response variables to soil S. The lack of yield response despite the improvement in soil S content, subsequently, corn and soybean S uptake possibly was an indication of either luxury consumption of S and/or weather interference during the critical crop growth stages that masked the effects of S source and rate.

Date

1-23-2023

Committee Chair

Tubana, Brenda

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