Applications of Gypsum and Ammonium Sulfate Change Soil Chemical Properties of a Salt-Affected Agricultural Soil

Guilherme Bossi Buck,Lincoln Zotarelli,Edson Marcio Mattiello,Gustavo Franco De Castro

doi:10.5539/jas.v12n7p1

Abstract

Irrigation water with high electrical conductivity (EC) compromises the sustainability of agricultural soils. Calcium sulfate (CS) or gypsum is commonly used on removal of soluble ions such as sodium (Na), however, large applications of CS can affect soil pH, EC, and nutrient availability to plants. The objective of this study was to investigate the effects of CS and ammonium sulfate (AS) rates on the soil pH, EC, and exchangeable cations in a salt-affected agricultural soil. Samples from the 0-20 cm soil depth layer were collected from an agricultural soil reported to have low potato yield due to high EC irrigation water. Soil was incubated with rates ranging from 0 to 4000 kg ha-1 of CS and 0 to 600 kg ha-1 of nitrogen (N) using AS. The treated soil was incubated for 60 d at 25 &ordm;C and moisture was maintained at 60% of soil field capacity. After incubation, the soil was analyzed for pH, EC, Na, manganese (Mn), and zinc (Zn). Increasing rates of CS resulted in a small decrease in soil pH and a significant linear increase in soil EC, while the application of AS linearly reduced the soil pH and quadratically increased soil EC. The application rate of 200 kg ha-1 of N as AS resulted in a decrease of soil pH from 5.9 to 5.2, while the EC increased from 1.3 to 3.0 dS m-1. Extractable Na increased linearly with the application of AS due to its effect on the soil pH. The soil extractable Mn and Zn were not affected by the application of CS. Applications of AS resulted in a linear increase in soil extractable Mn and Zn concentrations, respectively. Results from this incubation study suggest that the use of large rates of CS for consecutive years may further impair soil conditions for cropping in areas with high EC in the irrigation water.

Highlights

Groundwater is an important natural resource for domestic, agricultural, industrial, and public use in Florida as well as other parts of the world
The plant tissue analysis (Table 1) confirmed that the three areas with various yields did not present any deficiencies related to N, P, K, Ca and Mg according to the critical levels reported by Hochmuth et al (2018), which indicates that the low potato yield was likely due to high soil electrical conductivity (EC) and Na+ in the 0-20 cm soil depth layer
The values of nutrients and Na+ from the initial sampling were higher compared to the soil sampling performed after the potato harvest (Table 2), which was used for the incubation study

Summary

Introduction

Groundwater is an important natural resource for domestic, agricultural, industrial, and public use in Florida as well as other parts of the world. Saltwater intrusion occurs naturally to some degree in most coastal aquifers, owing to the hydraulic connection between groundwater and sea water. Activities like intensive groundwater pumping for public, industrial, and agricultural consumption can exacerbate saltwater intrusion (Barlow, 2003; Xiao et al, 2019). In northern St. Johns County, in Florida, the water type from the Upper Floridian Aquifer has high concentrations of calcium (Ca2+), magnesium (Mg2+) and sulfate (SO42 ̄) and the presence of sodium chloride (NaCl) represents a mixing of saltwater with fresh aquifer water (Spechler, 1994)

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