Abstract
ABSTRACT Considering the importance of nutrients in the soil for the plants development and the soil quality conservation and the quantification relevance of them for proper soil management, the aims of this research were: (i) to quantify the clay loss, adsorbed and soluble P from interrill erosion influenced by the presence of sugarcane residues on the ground surface; (ii) to determine the minimum percentage of residues to be maintained on the soil surface to not enrich the eroded sediment by clay and soluble P (Psed) and adsorbed (Pads). The experimental area is located in Guariba - SP, with soil classified as Red Dystrophic Oxisol. The experiment was designed based on results of previous experiments with residue analysis of variance for 40 plots. These experiments were conducted by our research group, which provided field representation and the establishment of a minimum number of degrees of freedom necessary to ensure normal distribution of results and variance homoscedasticity. The experimental design was completely randomized in a factorial design, 5 treatments with straw sugarcane and 3 repetitions, totaling 15 plots. In the treatments, the straw was manually distributed across the surface of the soil in amounts of 0; 0.16; 0.35; 0.52 to 0.7 Kg by plot, giving 0% coverage (SC0), 25% (SC25), 50% (SC50), 75% (SC75) and 100% (SC100), respectively. The experimental plots were subjected to simulated rain with average intensity of 60 mm h−1 for 65 minutes. To avoid enrichment ratio (ER) of the sediment eroded by Psed, Pads and clay, a minimum soil surface coverage (SC) of 42% is necessary.
Highlights
Erosion is a natural physical process that consists of the breakdown, transportation and deposition of soil particles, which begins with the impact of raindrops on the soil surface, when associated with agricultural activities can be intensified due to the use of inappropriate agricultural practices and the reduction of vegetation cover (SILVA & CONCEIÇÃO, 2011)
The increase of the soil surface coverage caused a significant exponential decrease in interrill erosion rate and in the sediment concentration (Figure 1).With 100% of coverage, there was 0.25 g of soil sediment being transported per liter of flood, while in the bare soil were dragged 9.03 g L-1
When 50% of straws were kept on the soil surface, the Di was reduced by 91.4% when compared to the value obtained for bare soil
Summary
Erosion is a natural physical process that consists of the breakdown, transportation and deposition of soil particles, which begins with the impact of raindrops on the soil surface, when associated with agricultural activities can be intensified due to the use of inappropriate agricultural practices and the reduction of vegetation cover (SILVA & CONCEIÇÃO, 2011). The transported particles from the soil superficial erosion promote pollution and siltation of rivers (PINHEIRO et al, 2013) They decrease soil fertility and cause the accumulation of waste and chemical pesticides, damaging aquatic flora and fauna (RAMOS et al, 2012) resulting in a lower O2 concentration in the water, characterizing a phenomenon called eutrophication (FAZLI et al, 2011; PINHEIRO et al, 2013). With this phenomenon there is the proliferation of aquatic weeds and algae that can produce harmful toxic substances to health, changing the water quality (BARRETO et al, 2013)
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