The dependence of soil organic matter and crop productivity in maize monoculture

Monoculture is cropping system that is still using on the broadest areas for maize production in Serbia and in the world. This technology has many disadvantages, due to the negative impact on environment, with increased inputs of agro-chemicals and lower yields achieved. However, some measures (like application of farmyard manure and bio-fertilizers that decompose crop residues) could improve maize productivity and restore soil fertility, even in negative agro-ecological conditions. Soil organic matter plays an important role in maintenance of soil fertility, contributing to carbon cycling in the soil. The hybrid ZPSC 684 Ultra (in order to conduct perennial grass weed control with the application of cycloxydim) was grown in long-term monoculture during period 2012-2016. The soil type at the experimental field is slightly calcareous chernozem with 53% sand, 30% silt, 17% clay and soil structure is silty clay loam with pH 6.9 and moderate drainage. The trial included application of farmyard manure in the amount of 60 t ha-1 (M) in 2011, 2014 and trial without manure application (MØ). The application of bio-fertilizer Bioplug (for crop residues decomposition) is the second factor with three levels: application in amount of 2.5 l ha-1 (BF1), 5 l ha-1 (BF2) and without it (BFØ). Mineral fertilizer application included NPK in autumn (N:P:K= 15:15:15, 1709 kg ha-1) and Urea (320 kg ha-1) in spring (MF), and control - without mineral fertilizers. Soil organic matter (from 0-30 cm layer) was determined at the beginning of vegetation every year and maize grain yield was measured after harvesting. Soil organic matter varied across seasons and experimental variants from 1.08% (combination MØBF2-control) up to 5.58% (in combination MØ-BFØ-control), both in 2016. Averagely, higher soil organic matter was determined in trial with manure, as well as BFØ and control. Grain yield also expressed significant variations under the influence of year, mineral fertilizer and interactions year x bio-fertilizer, year x mineral fertilizer, bio-fertilizer x mineral fertilizer and interaction of all three treatments, but mainly in treatment without manure application. In treatment with manure, only year and its interaction with bio-fertilizer and mineral fertilizer showed significant impact on grain yield variability. The highest values of grain yield were achieved in 2014, as a season with the lowest average monthly temperature and the highest precipitation amount, as well as BF2 and MF treatments, particularly in the part of trial with manure application. The significant and negative correlations between soil organic matter and maize grain yield exist in MØ and M treatments, with notice that the highest yield values were achieved when soil organic matter is in range 2.5-4.5% (MØ treatment) and 2.5-5% (M treatment). This means that improved mineralisation, as in BF2 treatment, in combination with mineral fertilizers and particularly manure application reflects positive on maize yielding potential, even in meteorologically unfavourable seasons, like 2012. Manure partially diminishes the influence of other factors, such as application of mineral and bio-fertilizer. It could be concluded that soil organic matter and its mineralisation plays an important role in expression of maize yielding potential. Low organic matter, or its high values reveals negatively on maize yielding.