Potential of Lacto-Gypsum as an Amendment to Build Soil Quality

Giulia Bondi,Hilda Keane,Parikshit Sawdekar,Owen Fenton,David P Wall

doi:10.3389/frsus.2020.625727

Abstract

Strategies for the use of amendments on agricultural soils are needed to help build resilience against potential soil threats. Gypsum is commonly applied to improve soil quality and nutrient supply. However, the sustainability and environmental safety of some gypsum sources is uncertain. This study aims to i. characterize a new by-product, lacto-gypsum, derived from a dairy whey side stream over a 1 year pilot production cycle and ii. assess the temporal variability of the raw form of lacto-gypsum and the stability of its physico-chemical and compositional properties when stored under three potential storage regimes. Results showed that lacto-gypsum compares favorably with conventional equivalents in terms of nutrient and trace element concentrations and represents an environmentally safe material free of contaminants. Storage form did not affect its main physico-chemical characteristics over time and the raw lacto-gypsum remained stable up to 20 days when stored at 4°C. In contrast to conventional gypsum, the lacto-gypsum had very low pH. In general this new lacto-gypsum shows potential as a suitable product for use as a soil amendment or as an acidification agent for animal slurry to reduce ammonia gas emissions during storage. However, further evaluation of this by-product in real life scenarios is required.

Highlights

The application of amendments to agricultural soils can help to build soil resilience against potential soil threats such as soil compaction, erosion, soil fertility or organic matter (OM) loss (Amoah-Antwi et al, 2020)
From a chemical perspective gypsum is proven to be an excellent source of Ca and S both of which are beneficial for plant growth (Dick et al, 2006; Batool et al, 2015; Walia and Dick, 2016)
The lacto-gypsum shows low total C (1.5%) and total N (0.4%), concentrations similar to the ones reported for natural gypsum (Mupambwa et al, 2015) but, in general, higher than values typically found in flu-gas desulfurization (FGD) gypsum (Wang and Yang, 2018) (Tables 1, 2)

Summary

Introduction

The application of amendments to agricultural soils can help to build soil resilience against potential soil threats such as soil compaction, erosion, soil fertility or organic matter (OM) loss (Amoah-Antwi et al, 2020). The Ca present in gypsum binds OM to clay, thereby protecting it and preventing carbon (C) losses (Walia and Dick, 2018). Application of gypsum as amendment for the treatment of alkali and saline soils is a widely used practice (Oster and Frenkel, 1980; Shainberg et al, 1989; Dick et al, 2006). In terms of physical quality, the Ca in gypsum increases the aggregation potential of soil particles making the soil more resilient against compaction (Watts and Dick, 2014; Walia and Dick, 2019)

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