Chemical, Biological, and Biochemical Parameters of the Soil P Cycle After Long-Term Pig Slurry Application in No-Tillage System

Abstract

ABSTRACT:In Southern Brazil, agricultural soils are often treated over long periods with annual pig slurry (PS) applications, and their influence on soil nutrient dynamics should be monitored. This study aimed to evaluate the P forms accumulated in the soil and some biological and biochemical parameters of the P cycle after 19 successive PS applications over eight years, in a no-tillage (NT) system. Pig slurry was applied at rates of 0, 20, 40, and 80 m 3 ha -1 per crop. Several P forms (available P, microbial P, phosphatase enzyme, total organic and inorganic P) in the 0.00-0.05 and 0.05-0.10 m soil layers were analyzed. Increases up to 5,523 % in available P, 308 % in microbial P, 104 % in phosphatase enzyme activity, 91 % in organic P, 251 % in inorganic P, and 19 % in Total-P were observed in the 0.00-0.05 m soil layer in response to the highest PS rate compared to the treatment with no PS. Results also indicated that P added via PS was preferentially accumulated in the inorganic fractions (83-98 %). The increase in organic P was limited by the increase in soil organic carbon. The increase in soil microbial biomass-P was more influenced by available P, while the increase in phosphatase enzyme activity was more related to the increase in organic P and C. Therefore, PS applied to the soil affected the chemical, biological, and biochemical components of the soil P cycle.Results indicate that even half of the PS rate normally used by farmers (20 m 3 ha -1) poses a high risk of pollution of water bodies by runoff from these soils.

Phosphorus fractions in soil fertilised with organic waste

“…In turn, Kashem et al (2004) suggest that application of cattle manure could decrease the soil content of soluble phosphorus, concurrently with an increase in the less stable forms of P. This dependence is attributed to the activity of soil microorganisms converting labile phosphorus compounds into organic compounds, which in turn is triggered by a higher amount of harvest residue left by manure fertilised crops, as well as the broad C/P ratio in this fertiliser. According to Tiecher et al (2017), a rise in the P-organic content is restrained by the amount of Corganic in soil. Generally, an increase in P-total is accompanied by greater accumulation of labile fractions of this element, and their quantities depend on the N:P ratio and on the content of P in the fertiliser.…”

Characteristics of Phosphorus Loss from Organic Farming and Forestry Land under Simulated Rainfall in the Mountainous Areas of Western Anhui

“…Owing to the unique topography and local farming habits in the western Anhui Mountain, the fertilization method of Cuilan tea is a hole application, so the soil phosphorus content is high. Continuous fertilizer application will migrate organic phosphorus to the deeper ground [33]. Soluble mineral substances in the soil will increase the leaching of phosphorus by leachate.…”

Establishing environmental soil phosphorus thresholds to decrease the risk of losses to water in soils from Rio Grande do Sul, Brazil

“…Soil with lower availability of P presented reduction fractions of it as soluble in water, due to the high affinity of the nutrient to adsorption sites (Gatiboni et al, 2015;Campos et al, 2018). However, the constant addition of P leads to a gradual reduction of the potential for soil retention and, consequently, to the increase in forms of higher lability (Alleoni et al, 2014;Roy et al, 2017;Tiecher et al, 2017;Campos et al, 2018). The increase of P lability is due to the saturation of adsorption sites and to the increase in the negative electrical potential of soil (Oliveira et al, 2014;Barrow, 2015).…”