Influence of wheat crop on carbon and nitrogen mineralization dynamics after the application of livestock manures

The growing global demand for livestock products has increased the scale of livestock farming. The management and disposal of large quantities of manures has become a serious environmental challenge. At the same time, there is a need for providing nutrients to plants in a sustainable way, in particular nitrogen (N). In this sense, a better understanding of N availability from livestock manures when applied to the soil will help to improve their use as fertilizers. It was hypothesized that the mineralization dynamics of the manures might be different depending on their composition and the presence of wheat. This work is performed to evaluate the effect of cattle manure (CM), hen manure (HM), and dairy slurry (DS), at two N rates when wheat (Triticum aestivum L.) was grown or not (bare soil) on i) protease, amidase, and urease activities and ii) dissolved organic carbon (DOC) and mineral N dynamics in soil solutions. A pot experiment was carried out in a greenhouse, and CM, HM, and DS were applied at 170 and 340 kg N ha(-l)- rates in the presence or absence of plants. Soil cores and solution samples were taken throughout the wheat growing period. Protease and amidase activities were higher for CM and DS applied at the highest N rate, respectively. Urease activity increased when wheat was grown with the lower N rate in the three manures. The DS caused higher concentrations of DOC and ammonium the day after its application than when HM and CM were used. During the first month, the nitrate concentration increased and was highest with HM, followed by DS and CM. However, the nitrate concentrations decreased in the treatments with plants after tillering. Wheat N uptake at harvest was highest with HM, followed by DS and CM. Mineralization dynamics were different in the three manures, which implies that the application times must be different.