Impact of long‐term mineral and organic fertilizer application on the water stability, wettability and porosity of aggregates obtained from two loamy soils

Abstract

Summary The impact of fertilizer application on soil aggregate stability is of increasing interest to soil scientists. Aggregate water stability depends primarily on soil organic matter. We studied silty loam and loamy sand aggregates from three long‐term fertilizer treatments (control, pig manure and NPK) which significantly altered the quantity of organic matter. A new approach to examining aggregate stability was used: soil aggregates were immersed in methanol‐water solutions with methanol at 0, 20, 40 and 60% concentration (C), and non‐disrupted aggregates were separated after 30 minutes. The aggregate resistance R(C) against each solution was taken as the percentage of stable aggregates. Overall resistance of the aggregates was taken as the Rtot parameter given by the product of four R(C) values. The R(C) values of all aggregates were positively correlated with C. The R(60) values were independent of the applied fertilizer. The R(0) value for silty loam aggregates ranged from 28% (pig manure) to 7% (NPK), while that for loamy sand equalled 7–9% in all cases. The R(20) values were most effective at differentiating the soils and the fertilizer treatments. However, the Rtot value was a better indicator of aggregate stability. Greater differences in stabilities of aggregates were noted in loamy sand. Mineral fertilizer application seemed to decrease aggregate resistance in both soils. Total organic carbon and nitrogen content in all non‐disrupted aggregates were negatively correlated with methanol concentration (C) of the solution applied for aggregate separation. The largest decrease was for the pig manure treatment, and the smallest was for the control. Porosity and pore size distributions of the aggregates were derived from micro‐tomography and approximated to lognormal pore size distributions. Larger porosities and pores were found in water‐stable aggregates than in methanol‐stable aggregates. It seems that the dominant mechanisms for aggregate instability during fast wetting were not related only to the pore air compression, but to weakening of attractive forces between aggregate particles by water.

How dose of biochar and biochar with nitrogen can improve the parameters of soil organic matter and soil structure?

“…Organic fertilizers increase the stock of SOM, through which they positively influence the soil physicochemical properties, such as the formation of favourable structure (Czachor et al 2015). In our study biochar also affected the crusting index (Table 2).…”

The interaction of soil aggregate stability with other soil properties as influenced by manure and nitrogen fertilization

“…The high annual variability of WSA stability found in this study was most likely caused by the differences in wetting-drying cycles, root development during the growth period and freeze-thaw cycles between the winters. With wetting, air that was entrapped inside the pores of aggregates was rapidly released, which resulted in the collapse of weaker macro-aggregates (Czachor et al, 2015). Additionally, because drying does not occur evenly across the structure, cracks may have developed (Tang et al, 2016), shearing the aggregates apart.…”

“…Manure has the added benefit of further increasing WSA stability by enriching soil with additional organic matter and plant nutrients, stabilizing soil acidity and increasing microorganism community diversity. Some research even suggests that nitrogen fertilizers may decrease WSA stability (Czachor et al, 2015). With different fertilizers the soil is enriched by cations Ca 2+ , Mg 2+ and K + from which extensive K + can lead to reduction of soil structure, dispersion of clay particles; especially if K + concentration is higher relative to Ca 2+ and Mg 2+ concentrations (Rengasamy, Marchuk, 2011).…”

Soil Organic-Matter in Water-Stable Aggregates Under Different Soil-Management Practices

“…The complexity of the chemical and physical effects of fertilisers has resulted in variable effects of fertilisation on the aggregates. There have been reported negative impacts of the use mineral fertilisers on aggregate resistance (Czachor et al 2015). However, the fertiliser ap- where: G -control; T -tillage; T+FYM -tillage+farmyard manure; G+NPK3 -doses of NPK fertilisers in 3 -rd intensity for vineyards; G+NPK1 -doses of NPK fertilisers in 1 st intensity for vineyards; WSA ma -water-stable macro-aggregates; WSA mi -water-stable micro-aggergates.…”