Abstract
Organic matter (OM) and nutrient nitrogen (N) play vital roles in the fertility and production of soil in accordance with goals of efficient environmental protection. This study aimed to show the extent to which N delivery can contribute to improving nitrogen fertilizer requirements (NFR) through comparative analysis of OM and N. Systems determining the NFR in agricultural practices have thus far been challenged to estimate the annual rate of mineralization of the soil. OM and N turnover was investigated through an available evaluation consisting of 546 representatively distributed permanent test and observation plots (TP) of the German Federal State of Saxony farms. A solid database of at least 10-year field plot card records from 2001 to 2010 was selected for the analysis. A program (BEFU) widely used in agricultural practice, along with the simplified process model CCB, were applied. For the calculation of the amount of mineral N fertilizers used, the results of three different methods for determining the NFR were compared with each other. The determination of the farmers’ demand (=actual condition of the TP) with a mean value of 132 kg N ha−1 did not show a large difference between the calculated values with 137 kg N ha−1 by the BEFU program. Based on the available results for the most important crop species cultivated in Saxony, there were clear differences in the considerations of the N delivery from the soil. The BEFU program was able to calculate an average N delivery of 17 kg N ha−1 from tabulated data, whereas with the CCB process model, 66 kg N ha−1 of mineralization was determined with a distinct higher deviation by taking into account the 10-year field histories. Using the N delivery of the TP by the CCB model, a clear reduction of the mean N fertilization level, to about 80 kg N ha−1, was therefore achieved. These differences were particularly large for TP with organic fertilization (livestock), at a relatively low N fertilization level, and for certain crop species. With a high standard deviation, the average savings potential of mineral N fertilizers was 52–57 kg N ha−1. After including the corrected values for the N mineral fertilization, a decrease in the N balances by an average of 20–25 kg N ha−1 was ultimately achieved. In particular, the heavily oversupplied plots with D and E classification decreased by approximately 50%. The results of our study demonstrate clear improvements; therefore, increased efforts should be made in the future to optimize the determination of NFR using applicable methods that consider N mineralization in agricultural practice and consultation.
Highlights
Central European agriculture is facing major challenges
Taking into account the 10-year study cycle of the field records, nitrogen fertilizer requirements (NFR) were calculated for six cultivated crops, which come from a total of n = 2424 harvest years and correspond to a share of almost 70% of the total cultivation cycles and 390 test and observation plots (TP)
For the sites and harvest years, the BEFU fertilizer requirement calculated for the individual crops deviates only slightly from the average of the N-mineral fertilizer used by the farmers
Summary
Central European agriculture is facing major challenges. Agriculture should supply a continuously growing population with high quality food and increasingly provide renewable resources for energetic and industrial use. In view of the ongoing non-agricultural land consumption and limited resources, these requirements can often only be met by increasing land intensity and productivity. There are increasing calls to minimize the negative effects of agricultural production on the environment [1,2,3]. The long-term securing of the fertility and productivity of soil must be in accordance with the goals of efficient environmental protection, in particular, that of sustainable groundwater. For this reason, soil organic matter (OM) and the nutrient cycle of agricultural holdings are the focus of this work
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