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Purpose In Argentina, pig slurry (PS) is spread in surface with N losses in ammonia form. Different methods to decrease these emissions are available, but there is poor information about their impacts on the soil-plant system. The objective of this study was to compare the effects of different PS application methods on the soil quality in a maize-soybean cropping sequence. Methods PS application methods were evaluated: acidified (AS), incorporated (IS), surface (SS), mineral fertilization (MF) and control (C). The experimental design was arranged in a randomized block with three replicates. Chemical parameters and microbiological parameters were determined. Also, grain yields and N uptake were measured. Results IS caused increases in anaerobic nitrogen and basal respiration of soil on soybean. Treatments with PS and/or FM showed lower values in pH than C in both crops, and higher electrical conductivity only in maize. SS treatment showed higher Pe on soybean, indicating a maintenance of the P levels with respect to those in MF and C. The concentration of NO3- increased with MF in both crops. In maize, MF presented similar concentrations to AS and SS. IS increased grain yields of maize by 16 %, whereas SS and AS increased yields of soybean by 112% and 79%, respectively, compared to C. Conclusions The different PS application methods had similar effects on most of the indicators of soil quality. In maize, IS and AS were more efficient in retaining N within the soil-plant system, whereas, in soybean, the SS led to higher yields.

Purpose In Argentina, pig slurry (PS) is spread in surface with N losses in ammonia form. Different methods to decrease these emissions are available, but there is poor information about their impacts on the soil-plant system. The objective of this study was to compare the effects of different PS application methods on the soil quality in a maize-soybean cropping sequence. Methods PS application methods were evaluated: acidified (AS), incorporated (IS), surface (SS), mineral fertilization (MF) and control (C). The experimental design was arranged in a randomized block with three replicates. Chemical parameters and microbiological parameters were determined. Also, grain yields and N uptake were measured. Results IS caused increases in anaerobic nitrogen and basal respiration of soil on soybean. Treatments with PS and/or MF showed lower values in pH than C in both crops, and higher electrical conductivity only in maize. SS treatment showed higher Pe on soybean, indicating a maintenance of the P levels with respect to those in MF and C. The concentration of NO3 - increased with MF in both crops. In maize, MF presented similar concentrations to AS and SS. IS increased grain yields of maize by 16 %, whereas SS and AS increased yields of soybean by 112% and 79%, respectively, compared to C. Conclusion The different PS application methods had similar effects on most of the indicators of soil quality. In maize, IS and AS were more efficient in retaining N within the soil-plant system, whereas, in soybean, the SS led to higher yields. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory investigations were performed to estimate the potential mobility of arsenic (As) from a highly contaminated gold-mining soil under bio-oxidative aerobic conditions as a potential remediation process. The selected soil was sampled from a gold-mining site in the South of France. It contained 27700mgkg−1 total As, with only 0.01% present under water-soluble forms. The nature of the immobilization mechanisms was identified by using complementary physical and chemical techniques. As was found to be strongly associated to iron (oxy)hydroxide solid phase by adsorption and/or co-precipitation. Determination of iron (Fe) and As mobility as a function of pH showed that the release of As was related with the dissolution of Fe (oxy)hydroxide at very low pH values. Bioleaching experiments were conducted with the objective to enhance the mobilization of As from the source material via biological oxidation of elemental sulfur (S°) into sulfuric acid by autotrophic exogenous or indigenous bacteria naturally located in the soil (i.e. Acidithiobacillus species). Tests conducted at 30°C in shaker flasks supplemented with S° resulted in very acidic (pH<1) and oxidative conditions (oxidation/reduction potential (ORP) around +800mV vs. NHE) and induced the extraction of up to 35% of As over 84 days of incubation. Under the experimental conditions of the study (batch experiments), As mobilization was strongly correlated to the dissolution of Fe solid phases. As mobilization was probably limited by the saturation of the liquid phase. Chimiolithotrophic exogenous population appeared to have a minor effect on As bioleaching. Endogenous populations were shown to rapidly develop their capacity to oxidize S° and mobilize As from the mining soil in the form of arsenate when elemental S° was supplemented. The use of microbial population adapted to high As concentrations reduced significantly the lag period to reach optimal pH/ORP conditions, and increased As extraction rate to a maximum of 41% within 70 days of incubation. However, As reprecipitation was subsequently observed, suggesting that the solution should be periodically replaced in order to optimize the process. [Copyright &y& Elsevier]