Abstract
The application of animal manure to soil can increase phosphorus availability to plants and enhance transfer of the nutrient solution drained from the soil surface or leached into the soil profile. The aim of this study was to evaluate the effect of successive applications of organic and mineral nutrient sources on the available content, surface runoff and leaching of P forms in a Typic Hapludalf in no-tillage systems. Experiment 1 was set up in 2004 in the experimental area of UFSM, in Santa Maria (RS, Brazil). The treatments consisted of: control (without nutrient application) and application of pig slurry (PS), pig deep-litter (PL), cattle slurry (CS), and mineral fertilizers (NPK). The rates were determined to meet the N crop requirements of no-tillage black oat and maize, grown in the 2010/2011 growing season. The soil solution was collected after each event (rain + runoff or leaching) and the soluble, particulate and total P contents were measured. In November 2008, soil was collected in 2 cm intervals to a depth of 20 cm, in 5 cm intervals to a depth of 40 cm, and in 10 cm intervals to a depth of 70 cm. The soil was dried and ground, and P determined after extraction by anion exchange resin (AER). In experiment 2, samples collected from the Typic Hapludalf near experiment 1 were incubated for 20, 35, 58, 73 and 123 days after applying the following treatments: soil, soil + PS, soil + PL, soil + CS and soil + NPK. Thereafter, the soil was sampled and P was analyzed by AER. The applications of nutrient sources over the years led to an increase in available P and its migration in the soil profile. This led to P transfer via surface runoff and leaching, with the largest transfer being observed in PS and PL treatments, in which most P was applied. The soil available P and P transfer via surface runoff were correlated with the amounts applied, regardless of the P source. However, P transfer by leaching was not correlated with the applied nutrient amount, but rather with the solution amount leached in the soil profile.
Highlights
More than 54 % of the swine production in Brazil is concentrated in the South of the country
The greatest increases were observed in the treatment with pig deep-litter (PL) application at a depth of 25 cm, while in the treatments pig slurry (PS), cattle slurry (CS) and NPK, the increases were significant to a depth of 14, 18 and 4 cm, respectively (Table 2)
One of the factors explaining this differentiated behavior is the total P contents (total P) quantity applied in each treatment from the beginning of the experiment (i.e., 393, 748, 288, and 223 kg ha-1 P with the application of PS, PL, CS and NPK, respectively), since the available P contents in the 0-10 cm layer were significantly correlated with the applied P quantities (Table 4)
Summary
More than 54 % of the swine production in Brazil is concentrated in the South of the country. The dairy industry of this region is responsible for around 32 % of the domestic milk production (Embrapa, 2012) These two activities generate large volumes of liquid or solid manure due to the high number of animals. The rate of manure application to the soil is established based on its percentage of dry matter, on the nutrient concentration and on the efficiency index. This index refers to the total quantity of nutrients contained in the manure which may be transformed from the organic to the mineral form during the period of crop development (CQFS-RS/SC, 2004). Among the methods used for evaluating P availability in the soil is the anion exchange resin (AER) method (Bolland et al, 1996; Berwanger et al, 2008; Guardini et al, 2012b), used for determining P availability to plants (CQFS-RS/SC, 2004) and as an indicator of the contamination potential in soils with sequential application of animal manure (Guardini et al, 2012b)
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