Aggregation Index and Carbon and Nitrogen Contents in Aggregates of Pasture Soils under Successive Applications of Pig Slurry in Southern Brazil

Abstract

Pig slurry (PS) applications affect soil aggregation and carbon and nitrogen contents in aggregates. The objective of this study was to evaluate changes caused by successive applications of PS and mineral fertilizer on soil aggregation and carbon (C) and nitrogen (N) contents in aggregates of a clayey Typic Hapludox cultivated with Cynodon dactylon cv. Tifton-85 in southern Brazil. The treatments consisted of six annual applications of PS (100, 200, 300, and 400 kg N ha−1) and urea (200 kg N ha−1), and a control with no fertilizer application. Soil samples were collected in March 2019 and evaluated for aggregate stability, through the geometric mean diameter of aggregates (GMD), and GMD sensitivity index (SIGMD), and mass of macro-, meso-, and microaggregates. Total organic carbon and nitrogen contents were determined in macroaggregates and microaggregates. Applications of PS to pasture soils increase dry matter production of Tifton-85 and can increase soil aggregation by increasing the mass of macroaggregates. The highest PS rates decreased aggregate stability, resulting in lower macroaggregate mass, GMD, and SIGMD, and higher microaggregate mass. PS applications to pasture soils can increase C and N contents in macro and microaggregates, and improve soil aggregation when using the rates of 100 or 200 kg N ha−1, mainly in subsurface layers.

Soil Aggregation and Associated Organic Carbon and Total Nitrogen in a Sandy Loam Soil under Long-Term Tillage Effects

“…The higher percentage of macro-aggregates found under no-till regimes has been attributed to a reduction in macro-aggregate turnover under this type of regime [45]. Macro-aggregate mass in the soil's surface layer is probably increased by the layer's high biomass content and root activity [49]. Zotarelli et al [50] found that cereal root systems positively influenced macro-aggregate formation, and a similar effect was observed in our experiment.…”

Changes in Dry Matter and Carbon, Nitrogen, and Sulfur Stocks after Applications of Increasing Doses of Pig Slurry to Soils with Tifton-85 for Six Years in Southern Brazil

“…The results found for S stocks were due to the accumulation of S from the PS applications over the years. Santos et al [44] found increases in sulfur contents in plants grown in an Oxisol fertilized with PS, which was reflected in the biomass production of Tifton-85 pastures. This was also found in the present study; the addition of S probably partly contributed to the higher mean DMP of Tifton-85 in treatments using PS.…”

“…Maize and oat crop rotations under the long-term application of PS were evaluated by Sacomori et al [42], who found an increase in soil organic carbon in the soil 5-10 cm layer for PS rates of up to 100 m 3 ha −1 , and by Mafra et al [43], who found increasing soil organic carbon contents and stocks as the PS rates and soil layers were increased. Santos et al [44] evaluated nutrient contents of an Oxisol fertilized with PS in the Cerrado biome, Brazil, and found no differences in N stocks; they attributed it to the PS rates applied, high organic matter contents, and leaching, since the N stocks were higher in the deeper layers; in addition, they found increases in sulfur contents in the plant biomass and attributed it to the high soil N, organic matter, and clay contents, which facilitate sulphate absorption; it reflected on the biomass production and nutrient content of the Tifton-85 pastures.…”

Crop Diversification Effects on Soil Aggregation and Aggregate-Associated Carbon and Nitrogen in Short-Term Rainfed Olive Groves under Semiarid Mediterranean Conditions

“…Soil Mean Weight Diameter (MWD) Equation ( 1), Geometric Mean Diameter (GMD) Equation ( 2) and GMD sensitivity index (SI GMD ) Equation ( 3) were calculated to analyse soil aggregate stability index [56,57]. The MWD, GMD and SI GMD were determined as follows:…”