Abstract
Successive applications of pig slurry to soils under no-tillage can increase the nutrient levels in the uppermost soil layers and part of the nutrients may be transferred to deeper layers. The objective was to evaluate the distribution of nutrients in the profile of a soil after 19 pig slurry applications under no-tillage for 93 months. The experiment was conducted from May 2000 to January 2008 in an experimental area of the Federal University of Santa Maria, southern Brazil, on a Typic Hapludalf. The treatments consisted of pig slurry applications (0, 20, 40 and 80 m³ ha-1) and at the end of the experiment, soil samples were collected (layers 0-2, 2-4, 4-6, 6-8, 8-10, 10-12, 12-14, 14-16, 16-18, 18-20, 20-25, 25-30, 30-35, 35-40, 40-50 and 50-60 cm). The levels of mineral N, available P and K and total N, P and K were evaluated. The 19 pig slurry applications in 93 months promoted migration of total N and P down to 30 cm and available P and K to the deepest layer analyzed. At the end of the experiment, no increase was observed in mineral N content in the deeper layers, but increased levels of available P and K, showing a transfer of N, P and K to layers below the sampled. This evidences undesirable environmental and economic consequences of the use of pig slurry and reinforces the need for a more rational use, i.e., applications of lower manure doses, combined with mineral fertilizers.
Highlights
Swine production in Brazil, as in the traditional swine-producing countries of the world, is an important income source of small farms, especially in the south of the country
Nitrification rates may vary from 0.98 to 1.53 kg ha-1 day-1 in manured soils, as observed by Aita et al (2006) in an assessment carried out four days after pig slurry applications of 40 and 80 m3 ha-1, respectively, and all ammoniacal N present in manure can be nitrified within 10 days after manure application (Chantigny et al, 2001)
Accumulation of N-NO3- in soil occurs in the first days after pig slurry application (Chantigny et al, 2004; Assmann et al, 2007; Adeli et al, 2008) and decreases over time due to its transfer by runoff (Smith et al, 2001a; Ceretta et al, 2010) and, mainly, percolation (Daudén et al, 2004; Basso et al, 2005; Bergström & Kirchmann, 2006), as it forms an outersphere complex with low binding energy with surface functional groups of reactive soil particles
Summary
Swine production in Brazil, as in the traditional swine-producing countries of the world, is an important income source of small farms, especially in the south of the country. Nitrification rates may vary from 0.98 to 1.53 kg ha-1 day-1 in manured soils, as observed by Aita et al (2006) in an assessment carried out four days after pig slurry applications of 40 and 80 m3 ha-1, respectively, and all ammoniacal N present in manure can be nitrified within 10 days after manure application (Chantigny et al, 2001). This rapid transformation of ammoniacal N to N-NO3significantly increases the concentration of N-NO3in soil (Loria & Sawyer, 2005). Accumulation of N-NO3- in soil occurs in the first days after pig slurry application (Chantigny et al, 2004; Assmann et al, 2007; Adeli et al, 2008) and decreases over time due to its transfer by runoff (Smith et al, 2001a; Ceretta et al, 2010) and, mainly, percolation (Daudén et al, 2004; Basso et al, 2005; Bergström & Kirchmann, 2006), as it forms an outersphere complex with low binding energy with surface functional groups of reactive soil particles
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