Soil physical attributes in forms of sowing the annual winter pasture and intervals between grazing

Milton Da Veiga,Alvadi Antonio Balbinot Junior,Daniela Aparecida De Oliveira

doi:10.1590/s1806-66902014000500005

Abstract

The sowing of winter pastures in areas used for summer grain production and their management under direct cattle grazing can cause changes in soil physical attributes, whose intensity depends on the degree of soil mobilization, grazing interval, stocking rate and weather. To study these aspects it was conducted over four years an experiment in a randomized block with split plots design and four replications. In the main plots were applied two forms of sowing the annual winter pasture (direct seeding and seeding + harrowing) and, in the subplots, four intervals between grazing (7, 14 and 28 days and ungrazed). Undisturbed soil cores were sampled at the end of each grazing cycle, in the 0-0.05 m layer to determine the saturated hydraulic conductivity and aggregate stability and in the layers of 0-0.05, 0.05-0.10, 0.10-0.15 and 0.15-0.20 m depth to determine bulk density and classes of soil pores. The direct seeding of annual winter pasture increases hydraulic conductivity and reduces soil bulk density in relation to seeding + harrowing while dairy cows trampling increases soil density and reduces macroporosity in the most superficial soil layer. The variation in climatic conditions among grazing cycles affects the soil physical attributes more markedly than forms of sowing and intervals between grazing of the annual winter pasture.

Highlights

The crop-livestock integration system (CLIS) is used in most small and medium farms of Southern Brazil, characterized mainly by the cultivation of annual pasture in the winter and the production of grain or silage in the summer
The form of sowing of the annual winter pasture did not affect the saturated hydraulic conductivity (SHC) in the 0.00-0.05 m layer and the SHC decreased with the reduction of the interval between grazing (Table 1), indicating that the cattle trampling reduces the amount and continuity of pores responsible for the rapid flow of water and air through the soil, as pointed out by Miguel et al (2009)
The SHC varied significantly between the years studied, with higher value in 2010, when there was the least amount of rainfall in the period in which the pasture was subjected to grazing, especially in the last month of that period (Table 2)

Summary

Introduction

The crop-livestock integration system (CLIS) is used in most small and medium farms of Southern Brazil, characterized mainly by the cultivation of annual pasture in the winter and the production of grain (maize, soybean or bean) or silage (maize or sorghum) in the summer This system results in the intensification of land use for the production of annual crops and increased and diversified the income in properties, improving the ecological and economic system (BALBINOT JUNIOR et al, 2009a; BARTH NETO et al, 2014; SALTON et al, 2013). The most common form of annual winter pasture sowing in Southern Brazil is the broadcast seeding and incorporation of seeds through harrowing This practice results in tilling the topsoil, resulting in reduction of its resistance to compression and increasing the potential for compaction by animal trampling (FLORES et al, 2007; VEIGA et al, 2007). The pasture usually is subjected to intensive grazing, resulting in high trampling and compaction of the soil surface (BERTOL et al, 1998), which can be exacerbated when the grazing is carried out with favorable moisture to soil deformation (HÅKANSSON; VOORHEES, 1998)

Methods

Results

Conclusion