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Fertilizers and Fertilization Strategies Mitigating Soil Factors Constraining Efficiency of Nitrogen in Plant Production
Fertilizer Use Efficiency (FUE) is a measure of the potential of an applied fertilizer to increase its impact on the uptake and utilization of nitrogen (N) present in the soil/plant system. The productivity of N depends on the supply of those nutrients in a well-defined stage of yield formation that are decisive for its uptake and utilization. Traditionally, plant nutritional status is evaluated by using chemical methods. However, nowadays, to correct fertilizer doses, the absorption and reflection of solar radiation is used. Fertilization efficiency can be increased not only by adjusting the fertilizer dose to the plant’s requirements, but also by removing all of the soil factors that constrain nutrient uptake and their transport from soil to root surface. Among them, soil compaction and pH are relatively easy to correct. The goal of new the formulas of N fertilizers is to increase the availability of N by synchronization of its release with the plant demand. The aim of non-nitrogenous fertilizers is to increase the availability of nutrients that control the effectiveness of N present in the soil/plant system. A wide range of actions is required to reduce the amount of N which can pollute ecosystems adjacent to fields.
Response of Wheat and Sugar Beet to Different Mineral–Organic Fertilization in a Long-Term Experiment
The effect of cyclic pig slurry (PS) application in long-term crop rotations with alfalfa is poorly recognized, particularly with regard to nitrogen use efficiency (NUE) in crops requiring relatively high nitrogen (N) inputs. A long-term field experiment was established in Prague-Ruzyně, Czechia, in 1955. The experiment evaluated the effects of eight fertilization combinations, involving PS application and various N, phosphorus (P) and potassium (K) rates (N0P0K0; N1P1K1; N3P2K2; and N4P2K2). The effect of fertilization was evaluated in a 9-year crop rotation, in which PS was applied only three times under root crops. Long-term different mineral fertilization treatments and the application of PS significantly affected the yield of the tested crops: winter wheat and sugar beet. The highest wheat yield (8.34 t ha−1) was observed in the PS+N3P2K2 treatment, while the highest beet yield (86.1 t ha−1) was recorded in the PS+N4P2K2 treatment. The differences compared with the absolute control (N0P0K0) were 62.3% and 40.5%, respectively. However, statistically significant differences between treatments with different NPK rates were recorded only in plots without PS. With increasing NPK fertilizer rates, the uptake of macronutrients by plants also increased. The only exception was calcium in sugar beet in PS plots. The total N accumulation in plants was proportionally related to the total N input to the soil–plant system (Nin). For winter wheat, this trend was beneficial, as it resulted in higher protein yield, whereas in beet, the sugar yield did not increase significantly when Nin exceeded 250 kg N ha−1. The obtained results indicate that, in the soil conditions of this experiment, N rates should be primarily balanced with appropriate rates of phosphorus.
Soil Fertility Clock—Crop Rotation as a Paradigm in Nitrogen Fertilizer Productivity Control
The Soil Fertility Clock (SFC) concept is based on the assumption that the critical content (range) of essential nutrients in the soil is adapted to the requirements of the most sensitive plant in the cropping sequence (CS). This provides a key way to effectively control the productivity of fertilizer nitrogen (Nf). The production goals of a farm are set for the maximum crop yield, which is defined by the environmental conditions of the production process. This target can be achieved, provided that the efficiency of Nf approaches 1.0. Nitrogen (in fact, nitrate) is the determining yield-forming factor, but only when it is balanced with the supply of other nutrients (nitrogen-supporting nutrients; N-SNs). The condition for achieving this level of Nf efficiency is the effectiveness of other production factors, including N-SNs, which should be set at ≤1.0. A key source of N-SNs for a plant is the soil zone occupied by the roots. N-SNs should be applied in order to restore their content in the topsoil to the level required by the most sensitive crop in a given CS. Other plants in the CS provide the timeframe for active controlling the distance of the N-SNs from their critical range.