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Potassium and Magnesium Balance the Effect of Nitrogen on the Yield and Quality of Sugar Beet
The yield-enhancing effect of nitrogen (N) in sugar beets depends on the appropriate balance of other nutrients, including potassium (K) and magnesium (Mg). To determine the effects of these nutrients on beet yield (BY), quality parameters, white sugar yield (WSY), and nitrogen use efficiency (NUE) indices, a three-year field study was conducted in western Poland. Eight different fertilization treatments with potassium salt (PS), Korn-Kali (KK), and magnesium sulfate (Mg) were tested, K0, K1 (PS), K2 (PS), K2 (PS) + Mg, K1 (KK), K2 (KK), K2 (KK) + Mg, K2 (KK) + Mg + FF, where 0, 1, and 2 are the K rates, respectively, for 0, 83, and 163 kg K ha−1, and FF denotes foliar fertilization with magnesium sulfate. Potassium fertilization, both in the form of PS and KK, along with additional application of magnesium sulfate, positively affected BY and WSY. However, the response to fertilization depended strongly on seasonal factors, such as weather and soil conditions. Compared to the treatment without potassium (K0), the average BY increased by 6.5–9.1%, and the WSY by 4.6–9.0%. Mineral fertilization had little effect on taproot quality parameters, including sucrose content. The exception was the concentration of α-amino-N, which significantly decreased with the application of K fertilizers. However, changes in α-amino-N content were not significantly related to WSY levels because this characteristic primarily depended on BY each year, and applying K and Mg to the soil improves NUE indices.
Soil Phosphorus and Potassium Fractions in Response to the Long-Term Application of Pig Slurry and NPK Mineral Fertilizers
The content of bioavailable forms of phosphorus (P) and potassium (K) in soil is essential for the proper functioning of agroecosystems. This study aimed to determine the effects of pig slurry (PS) and NPK mineral fertilizers on soil phosphorus (P) and potassium (K) fractions, the relationship between these fractions and basic soil agrochemical properties, and crop yield. The research material was collected from a long-term experiment established in 1955 in Prague-Ruzyně, Czechia. The effect of two constant factors was analyzed: manure application (control, PS) and different doses of NPK fertilizers (N0P0K0, N1P1K1, N3P2K2, and N4P2K2). A significant effect of fertilization on basic soil properties was demonstrated, including total soil carbon and nitrogen. PS and NPK fertilization also significantly affected the content of water-soluble and moderate labile fractions of P and K. These fractions were positively correlated with plant-available P and K (Mehlich 3). The best fertilization option, which resulted in the greatest increase in yield, was the use of PS and mineral fertilizers at the N3P2K2 level. Increasing the nitrogen dose to the level of N4 resulted in a decrease in the content of bioavailable forms of P and K in topsoil despite the application of PS.
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.
How Weather and Fertilization Affected Grain Yield and Stability of Winter Wheat in a Long-Term Trial in the South Moravian Region, Czech Republic
We evaluated the impact of weather and fertilization treatments (Control, PK, NPK1, NPK2, and NPK3) on winter wheat grain yields in a long-term trial in Ivanovice, Czech Republic, established in 1956. A total of 15 seasons were evaluated. The mean, maximal, and minimal temperatures in Ivanovice have been significantly increasing since 1961, with annual increases of 0.04 °C, 0.03 °C, and 0.05 °C, respectively. Precipitation has been decreasing annually by −0.54 mm (trend is insignificant). Four significant correlations between weather and grain yield were recorded. There were positive correlations between mean (r = 0.7) and minimal (r = 0.5) temperatures in November and negative correlations between mean temperatures in May (r = −0.6) and June (r = −0.6). The combination of naturally fertile chernozem soil and a beneficial preceding crop (alfalfa) enables sustainable cultivation of wheat, even without mineral fertilizers. The application of mineral nitrogen (N) significantly increases wheat grain yield and yield stability. Without mineral N or with high doses of mineral N, yield stability decreases. According to two response models (quadratic and quadratic-plateau), a reasonable dose of fertilizer is 107 kg ha−1 N for modern wheat varieties, corresponding to a yield of 8.1 t ha−1.
Soil and Plant Nitrogen Management Indices Related to Within-Field Spatial Variability
Field zones at risk of low nitrogen use efficiency (NUE) can be identified by analyzing in-field spatial variability. This hypothesis was validated by analyzing soil mineral nitrogen (Nmin) and several plant and soil N management indices. The research was conducted in Karmin (central Poland) during two growing seasons, with winter oilseed rape (2018/2019) and winter wheat (2019/2020). The study showed that the crop yield was positively related to Nmin. However, this N trait did not explain all the observed differences in the spatial variation of crop yield and plant N accumulation. In addition, the soil N management indices were more spatially variable during the growing season than the plant N management indices. Particularly high variability was found for the indices characterizing the N surplus in the soil-plant system. The calculated N surplus (Nb = N fertilizer input − N seed output) ranged from −62.8 to 80.0 kg N ha−1 (coefficient of variation, CV = 181.2%) in the rape field and from −123.5 to 8.2 kg N ha−1 (CV = 60.2%) in the wheat field. The spatial distribution maps also confirm the high variability of the parameters characterizing the post-harvest N surplus, as well as the total N input (soil + fertilizer) to the field with rape. The results obtained indicate that a field N balance carried out in different field zones allows a more accurate identification of potential N losses from the soil-plant system.
Improving Fertilizer Use Efficiency-Methods and Strategies for the Future
This editorial introduces our Special Issue entitled “Improving Fertilizer Use Efficiency—Methods and Strategies for the Future”. The fertilizer use efficiency (FUE) is a measure of the potential of an applied fertilizer to increase the productivity and utilization of the nutrients present in the soil/plant system. FUE indices are mainly used to assess the effectiveness of nitrogen (N), phosphorus (P), and potassium (K) fertilization. This is due to the low efficiency of use of NPK fertilizers, their environmental side effects and also, in relation to P, limited natural resources. The FUE is the result of a series of interactions between the plant genotype and the environment, including both abiotic and biotic factors. A full recognition of these factors is the basis for proper fertilization in farming practice, aimed at maximizing the FUE. This Special Issue focuses on some key topics in crop fertilization. Due to specific goals, they can be grouped as follows: removing factors that limit the nutrient uptake of plants; improving and/or maintaining an adequate soil fertility; the precise determination of fertilizer doses and application dates; foliar application; the use of innovative fertilizers; and the adoption of efficient genotypes. The most important nutrient in crop production is N. Hence, most scientific research focuses on improving the nitrogen use efficiency (NUE). Obtaining high NUE values is possible, but only if the plants are well supplied with nitrogen-supporting nutrients. In this Special Issue, particular attention is paid to improving the plant supply with P and K.
Effect of long-term application of pig slurry and NPK fertilizers on trace metal content in the soil
AbstractOne of the goals of sustainable agricultural production is to avoid soil contamination by elements defined as trace metals (TMs). The aim of this study was to assess the long-term impact of the use of pig slurry (PS) and NPK mineral fertilizers on the soil content of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn). In a 9-year crop rotation, PS was used three times only before root crops. The same four levels of NPK doses (N0P0K0, N1P1K1, N3P2K2, N4P2K2) were applied to both plots with and without PS. Soil samples were collected in early spring from topsoil (0–0.3 m) and subsoil (0.3–0.6 m). Three forms of TMs were determined in the soil: pseudo-total (Aqua regia); bioavailable (Mehlich 3 method) and readily bioavailable (mobile) forms (1 M NH4NO3). The tested factors did not have a significant impact on the Cd, Cu and Pb content, regardless of the form analyzed and the soil depth. PS application significantly increased the content of bioavailable forms of Zn regardless of the year, and the content of pseudo-total Zn only in the sugar beet year, i.e. after manure application. Increasing NPK doses increased the content of mobile Zn in the topsoil, especially in PS plots. A tendency to accumulate mobile forms of Cd and Pb was also observed on NPK-fertilized plots. Thus, long-term application of high NPK doses may increase the risk of contamination of the food chain with these metals. The content of mobile Cd and Zn was positively related to the content of total nitrogen in the soil and negatively related to pH.