Better Together: Water Treatment Residual and Poor‐Quality Compost Improves Sandy Soil Fertility

Abstract

Water treatment residual (WTR) is an underused clean water industry byproduct, generally disposed to landfill. This study assesses the benefits and risks of ferric-WTR as a soil amendment or co-amendment for plant growth in a nutrient-poor sandy soil. A 12-wk pot trial tested the efficacy of WTR and a locally available, low-quality, municipal compost as single (1, 5, and 12.5% dry mass) and co-amended treatments (1:1 WTR/compost ratio, at 2, 10, and 25%) on wheat (Triticum aestivum L.) growth in a sandy soil. The low total N content of the compost and low WTR P and K contents resulted in significantly lower (up to 50% lower, p < 0.05) plant biomass in single amendments compared with the control, whereas the highest co-amendment produced significantly higher plant biomass (33% higher, p < 0.05) than the control. This positive co-amendment effect on plant growth is attributed to balanced nutrient provision, with P and K from the compost and N from the WTR. Foliar micronutrient and Al levels showed no toxic accumulation, and co-amended foliar Mn levels increased from near deficient (20 mg kg −1 ) to sufficient (50 mg kg −1 ). Total WTR metals were well below maximum land application concentrations (USDA). Trace element bioavailability remained the same (Ni, Cu, and Hg) or significantly decreased (B, Al, Cr, Mn, Fe, Zn, As, and Cd; p < 0.05) during the pot trial. These results suggest, within this context, that a WTR-compost co-amendment is a promising soil improvement technology for increasing crop yields in sandy soils.

Waste to resource: use of water treatment residual for increased maize productivity and micronutrient content

“…However, compared to the control, the co-amendment of 10% Al-WTR, 10% C and P fertilizer resulted in higher maize growth and total biomass accumulation. This is in agreement with the work of Clarke et al (2019), which also found higher wheat biomass yield due to combined use of compost and WTR as a soil amendment compared with unamended soil. Similarly, Hsu and Hseu (2011) reported that co-application of compost and Al-WTR resulted in higher dry matter accumulation of Bahia grass (Paspalum notatum), although in their case, the resultant yield was not significantly different to sole Al-WTR treatments.…”

“…Alternatively, P fertilizer subsidies can be made available to farmers willing to incorporate Al-WTR in their farms. The higher N uptake due to the co-amendment in comparison with Al-WTR treatments reinforces the mutual benefits in nutrient supply when Al-WTR and compost are used together (Clarke et al, 2019). The surge in N uptake observed in the co-amendment due to the addition of fertilizer P was likely a result of an increase in P availability and thus improved root development which enabled the plants to take up more N from the soil.…”

“…Hsu and Hseu (2011) reported an increase in shoot biomass production of Bahia grass (Paspalum notatum) without changes in soil P availability due to co-application of WTR and pine bark compost. Recent work in Southern Africa has also proven that when WTR is used in combination with organic compost with a 1:1 co-application ratio, wheat (Triticum aestivum) productivity increased by 33% (Clarke et al, 2019). The resultant wheat growth was attributed to balanced nutrition, with P and potassium (K) from the compost and nitrogen (N) from WTR.…”

Innovative amendments derived from industrial and municipal wastes enhance plant growth and soil functions in potentially toxic elements-polluted environments

“…While the observed plant growth promotion effect could not be entirely attributed to one or another amendment, this latter study indicates that MSWC and WTR can be successfully used to increase crop yield in PTE-contaminated or degraded (i.e. nutrient poor) soils as also supported by other authors (Clarke et al, 2019;Hsu and Hseu, 2011;Zhao et al, 2016Zhao et al, , 2018.…”

Development of a method for the detection of zinc in Brassica oleracea using solid phase extraction and size-exclusion chromatography inductively coupled plasma mass spectrometry (SEC-ICP-MS)

“…Tris/HCl is a common buffer used to extract metal-bound species from different genotypes of wheat [18 , 24] , probably for its lysis properties which can explain its high extraction ability. Ammonium nitrate is used as a fertilizer in agriculture to provide a source of nitrogen which stimulates the plant growth, and it was chosen because it was considered a suitable solvent to extract water-soluble plant available trace elements from soil [21 , 22] and toxic elements from contaminated grassland soils to assess metal mobility in soil [19] . It was expected ammonium nitrate to extract Zn-bound species better than Tris/HCl, because the ammonia [23] formed by its dissociation leads to the formation of soluble metal ammine complexes, mainly occurring in the soil, which are available for plants [19] .…”