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Yield Predictive Worth of Pre-Flowering and Post-Flowering Indicators of Nitrogen Economy in High Yielding Winter Wheat
Indicators of nitrogen economy in winter wheat during vegetative development are a reliable tool for yield prognosis. This hypothesis was verified in a field experiment, carried out in the 2013/2014, 2014/2015, and 2015/2016 seasons. The field experiment, in a two-factor split-plot design, included the following systems of wheat protection (CFP): (i) N + micronutrients, (ii) N + fungicides, (iii) N + micronutrients + fungicides; and N rates: 0, 40, 80, 120, 160, 200, 240 kg N ha−1. The content and accumulation of N in wheat at the beginning of stem elongation and at heading were used for grain density and yield prediction. In the grain-filling phase, the stem N acted as a buffer, stabilizing yield at a high level. The condition for such action was the stem N equilibrium with the ear N at flowering. The N depletion from the leaves during the grain-filling period significantly depended on the grain density. The post-flowering uptake of N by wheat was affected by the grain density, which was affected by the N reserves in the stem. Yield forecast based on pre-flowering indices of nitrogen economy in cereals affects both agronomic decisions aimed at correcting the nutritional status of plants, and farm economics.
Nitrogen Cycle in Farming Systems
The challenge for people currently living on Earth is to develop a food production strategy to cover the food gap and at the same time maintain or even improve the soil use production potential [...]
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.
Does Elemental Sulfur Act as an Effective Measure to Control the Seasonal Growth Dynamics of Potato Tubers (Solanum tuberosum L.)?
The in-season dynamics of potato tuber biomass (TTB) growth requires effective nitrogen (N) control. This hypothesis was tested in 2006 and 2007. The two-factorial experiment with two rates of N (60, 120 kg ha−1) and sulfur (S; 0, 50 kg ha−1) was carried out in the split-plot design. The third factor was the sampling of plants at 10-day intervals. The collected plant material was divided into leaves, stems, stolons + roots, and tubers. The seasonal trend of TTB was linear, while the biomass of leaves, stems, and stolons + roots was consistent with polynomial regression models. TTB was controlled by (i) the date of potato growth after emergence, when the TTB exceeded the leaf biomass (DAEcrit); (ii) the stem growth rate; and iii) the share of stems in the total potato biomass. TTB growth was reduced when DAEcrit preceded the DAEop for leaf biomass, determining its maximum. This phenomenon appeared in 2007 on plots fertilized only with N. The absolute growth rate of the stem biomass, exceeding ¼ of that of the tuber biomass in the descending phase, resulted in an increased and prolonged share of stems in the total potato biomass, which ultimately led to a decrease in tuber yield. The use of sulfur to balance the N, applied effectively, controlled the growth rate of potato organs competing with tubers.
Determination of Mehlich 3 Extractable Elements with Visible and Near Infrared Spectroscopy in a Mountainous Agricultural Land, the Caucasus Mountains
Soil spectroscopy is a promising alternative to evaluate and monitor soil and water quality, particularly in mountainous agricultural lands characterized by intense degradation and limited soil tests reports; a few studies have evaluated the feasibility of VIS-NIR spectroscopy to predict Mehlich 3 (M3) extractable nutrients. This study aimed to (i) examine the potential of VIS-NIR spectroscopy in combination with partial least squares regression to predict M3-extractable elements (Ca, K, Mg, P, Fe, Cd, Cu, Mn, Pb, and Zn) and basic soil properties (clay, silt, sand, CaCO3, pH, and soil organic carbon-SOC), (ii) find optimal pre-processing techniques, and (iii) determine primary prediction mechanisms for spectrally featureless soil properties. Topsoil samples were collected from a representative area (114 samples from 525 ha) located in the mountainous region of NW Azerbaijan. A series of pre-processing steps and transformations were applied to the spectral data, and the models were calibrated and evaluated based on the coefficient of determination (R2), root mean square error (RMSE), and the residual prediction deviation (RPD). The leave-one-out cross-validated predictions showed that the first derivative spectra produce higher prediction accuracies (R2 = 0.51–0.91; RPD = 1.20–2.29) for most soil properties. The evaluation of the model performance with optimal pre-processing techniques revealed that both calibration and validation models produce considerable differences in RPD values associated with sample size and the random partition of the calibration or validation subsets. The prediction models were excellent or very good (RPD > 2.0) for CaCO3, SOC, sand, silt, Ca, and Pb, good or fair (1.4 < RPD < 2.0) for clay, K, Cd, pH, Fe, Mn, and Cu, and poor (1.0 < RPD < 1.4) for Mg, P, and Zn. Principal component and correlation, stepwise regression analysis, and variable importance in projection procedures allowed to elucidate the underlying prediction mechanisms. Unlike the previous studies, the spectral estimations of pH, Ca, Mg, P, Fe, Pb, and Cd concentrations were linked to their correlation with CaCO3 rather than soil organic matter, whereas Mg and P concentrations were also connected to Fe-oxides. Soil particle sizes contributed to predicting K concentration but confounded the prediction of P and Zn concentration. The weaker correlations of Mn, Cu or Zn with CaCO3, particle sizes, SOC, Fe, and spectral data yielded to their lower prediction accuracy. The major prediction mechanisms for M3-extractable elements relied on their relations with CaCO3, pH, clay content and mineralogy, and exchangeable cations in the context of their association with land use. The results can be used in mountain lands to evaluate and control the effect of management on soil quality indices and land degradation neutrality. Further studies are needed to develop most advantageous sampling schemes and modeling.
The Effects of Weather and Fertilization on Grain Yield and Stability of Winter Wheat Growing on Orthic Luvisol—Analysis of Long-Term Field Experiment
Based on a long-term experiment in Prague, established in 1954, we analyzed the effect of weather and seven fertilization treatments (mineral and manure treatments) on winter wheat grain yield (GY) and stability. In total, 23 seasons were analyzed, where a wheat crop followed a summer crop of potatoes. A regression analysis showed that, since the experiment started, there has been a significant increase in the annual daily maximum, average, and minimum temperature of 0.5 °C, and an increase in annual rainfall of 0.3 mm. Grain yield was positively associated with April precipitation, mean daily temperature in October, and daily maximum temperature in February. Yields were most stable between years with two fertilizer treatments that supplied a mean of 47 kg N ha−1yr−1, 54 kg P ha−1yr−1, and 108 kg K ha−1yr−1. The rate of N at which grain yield was optimized was determined according to the linear-plateau (LP) and quadratic response models as 44 kg N ha−1yr−1 for the long-strawed varieties and 87 kg N ha−1yr−1for short-strawed varieties. A gradual increase in yields was observed in all treatments, including the unfertilized control, which was attributed to improved varieties rather than to a changing climate.
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.
Productivity of Nitrogen Accumulated in Alfalfa–Grass Sward Cultivated on Soil Depleted in Basic Nutrients: A Case Study
The productivity of fodder legumes, based on internal sources of N, may be limited due to an insufficient supply of nutrients responsible for the efficient use of N accumulated by the crop during the growing season. Production risk occurs on soils that are naturally poor or depleted in nutrients that are decisive for the fixation and utilization of N2 by alfalfa. This hypothesis was validated on the basis of a field experiment with an alfalfa–grass mixture carried out over three main seasons (2012−2014) on soil low in available potassium (K), calcium (Ca), and sulfur (S). The experiment involved two factors that contained two levels of applied gypsum (GYP: 0, 500 kg ha−1) fertilized with P and K (POT: absolute control—AC, P60K0, P60K30, P60K60, and P60K120). In each main season of the alfalfa–grass mixture, the sward was mowed three times (three cuts). The total sward yield (TY) reached its maximum in the second main season (15.6 t DW ha−1), then it significantly decreased. The sward yield of the third cut was the main driver of the TY. The content of P in the first cut, and especially P and S in the third cut of the sward, affected the N:P and P:S ratios, which, in turn, determined the productivity of the alfalfa–grass mixture. The total amount of accumulated N (TN) in the sward significantly responded to gypsum and PK fertilizers. In the first and third main seasons, the highest TN was found on the plot fertilized with both gypsum and 120 kg K2O ha−1. In the second main season, the TY was determined by PK dose, being variable in successive years. The highest total N accumulation (TN) was recorded in the second main season. It reached 504 kg N ha−1 on the plots with GYP−0 and 436 kg N ha−1 for GYP−500. However, the corresponding TY was 16.7 and 17.3 t DW ha−1. This apparent discrepancy was due to the much higher productivity of N, which was 33.2 and 39.6 kg fodder DW ha−1 TN, respectively. These two characteristics clearly indicate that the productivity of the accumulated N by the alfalfa–grass sward was significantly restricted by the shortage of P and S. The studies clearly emphasized that the sward of the alfalfa–grass mixture grown on soil depleted in available K, Ca, and S responds significantly to the combined application of gypsum and potassium, but provides effective control of the P supply, even on soil rich in available P.
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.
Mutual Effect of Gypsum and Potassium on Nutrient Productivity in the Alfalfa–Grass Sward-A Case Study
It was assumed that the production of alfalfa in soils naturally poor in available nutrients, such as potassium (K) and calcium (Ca), depends on the use of fertilizers. This hypothesis was validated in an experiment with an alfalfa–grass mixture carried out in 2012, 2013 and 2014 on soil formed from loamy sand that had a low content of available Ca and K. The two-factor experiment consisted of two levels of applied gypsum as a source of Ca (0, 500 kg ha−1) and five levels of PK fertilizers (absolute control, P60K0, P60K30, P60K60 and P60K120). The total yield of the sward was determined by the main seasons of alfalfa–grass sward use. Gypsum application increased the yield by 1.0 t ha−1. The highest yield of 14.9 t ha−1 was obtained on the plot fertilized with P60K120. Based on the nutrient content in the sward, it was shown that the main yield predictor was the content of K in the first cut of sward use. The reliable yield predictors, based on the total accumulation of nutrients in the sward, turned out to be K, Mg and Fe. The nutritional quality of the alfalfa–grass fodder, based on the K/Ca + Mg ratio, depended mainly on the season of the sward use, which was substantially deteriorated by the K fertilizer. Gypsum did not control this process. The productivity of the nutrients taken up by the sward depended on the accumulated K. Its yield-forming effect was significantly limited by manganese deficiency. The use of gypsum positively affected the uptake of micronutrients, consequently increasing their unit productivity, especially of manganese. Optimization of the production of alfalfa–grass mixtures in soils poor in basic nutrients requires micronutrients to be taken into account. Their uptake by plants can be limited by high doses of basic fertilizers.
Prediction of Grain Yield and Gluten Content in Winter Bread Wheat Based on Nutrient Content in Plant Parts during the Critical Cereal Window
Reliable prediction of winter bread wheat grain yield (GY) and its qualitative parameters (crude protein (CP) and wet gluten (GL) content, wet gluten yield (GLY)) requires evaluation of the plant nutritional status in the Critical Cereal Window (CCW). The reliability of the forecast depends on the dedicated plant characteristics and the correct selection of the diagnostic plant parts. This hypothesis was verified in a one-factor field experiment carried out in the 2013/2014, 2014/2015, and 2015/2016 growing seasons. The field experiment included applying 0, 40, 80, 120, 160, 200, and 240 kg N ha−1. The N, P, K, Ca, Mg, Fe, Mn, Zn, and Cu content in wheat was determined in two growth stages: (i) beginning of booting (BBCH 40) and (ii) full flowering (BBCH 65). The evaluated plant components included the leaves and stem for BBCH 40 and the flag leaf, leaves, stem, and ear of BBCH 65. Grain yields were very high, significantly responding to the increased rates of fertilizer nitrogen (Nf), with a maximum yield of 11.3 t ha−1 achieved in 2014 (N rate of 209 kg N ha−1), 13.7 t ha−1 in 2015, and 8.6 t ha−1 in 2016 (N rate of 240 kg N ha−1). The CP and GL content also increased linearly in accordance with the Nf rates. At the beginning of the booting stage, the GY forecast based on the content of nutrients in the leaves or the stem was 94%. Meanwhile, a slightly higher yield prediction was obtained for leaves during the full flowering stage (95%). The key nutrients comprised K, Ca, and Mn, accounting for 93% of the GY variability. The accuracy of the GL prognosis at BBCH 40, regardless of the plant part, exceeded 99%. Three nutrients, namely, P, Mg, and Zn, explained 98% of the GL variability, and the GLY forecast was high (97%). Both wheat traits depended on Zn, which buffered the action of N and Mg. At the full flowering stage, the highest, yet slightly weaker, predictions of GL and GLY were obtained for leaves (95% and 92%, respectively). At this stage of winter wheat growth, the significant role of Zn and K and the buffering effect of Cu on the action of both nutrients was apparent. The obtained results unequivocally confirm that the game for winter wheat grain yield occurs within the Critical Cereal Window. In addition, the end result depends on the plant’s N supply during this period and the nutritional status of other nutrients. Application of 40–80 kg N ha−1 fertilizer critically impacted the GY and technological quality. Moreover, micronutrients, including Zn and Cu, influence the GY, GL, and GLY considerably. At the beginning of the booting phase (BBCH 40), winter wheat leaves serve as a highly reliable plant component indicator for evaluating nutrient content and quantitative (GY, GLY) and qualitative (GL) characteristics of grain. Moreover, analysis conducted during BBCH 40 allows the farmer to correct the nutritional status of the wheat, taking into account N and other nutrients as necessary.
Effective Control of the Nitrogen Gap—Higher Yields and Reduced Environmental Risk
The world’s growing demand for food cannot be met without the consumption of fertilizer nitrogen (Nf) [...]
Magnesium Fertilization Increases Nitrogen Use Efficiency in Winter Wheat (Triticum aestivum L.)
Wheat fertilized with Mg, regardless of the method of application, increases nitrogen fertilizer (Nf) efficiency. This hypothesis was tested in 2013, 2014, and 2015. A two-factorial experiment with three doses of Mg (i.e., 0, 25, and 50 kg ha−1) and two stages of Mg foliar fertilization (without; BBCH 30; 49/50; 30 + 49/50) was carried out. Foliar vs. in-soil Mg fertilization resulted in a comparable grain yield increase (0.5–0.6 t ha−1). The interaction of both fertilization systems increased the yield by 0.85–0.9 t ha−1. The booting/heading phase was optimal for foliar fertilization. Mg accumulation by wheat fertilized with Mg increased by 17% compared to the NPK plot. The recovery of foliar Mg was multiple in relation to its dose. The recovery of the in-soil Mg applied ranged from 10 to 40%. The increase in yield resulted from the effective use of N taken up by wheat. In 2014 and 2015, this amount was 21–25 kg N ha−1. The increase in yield resulted from the extended transfer of N from vegetative wheat parts to grain. Mg applied to wheat, irrespective of the method, increased the efficiency of the N taken up by the crop. Mg fertilization resulted in higher Nf productivity, as indicated by the increased nitrogen apparent efficiency indices.
The Influence of Calcium Sulfate and Different Doses of Potassium on the Soil Enzyme Activity and the Yield of the Sward with a Mixture of Alfalfa and Grasses
Between 2012 and 2015, a field experiment was conducted at the Brody Experimental Farm, Poznan University of Life Sciences, Poland. The following two experimental factors were used in duplicate: calcium sulfate (CaSO4) fertilization—two levels (0 and 500 kg ha−1); and potassium (K) fertilization—four levels (0, 30, 60, and 120 kg ha−1). The soil pH (in H2O) and enzyme activity (dehydrogenase, acid phosphatase, alkaline phosphatase) were determined. The potassium fertilizer had a significant influence only on the dehydrogenase activity, which increased with the dose of potassium. The research showed that the fertilization of the sward mixture of alfalfa and grasses with potassium doses of 60 and 120 kg ha−1 in the K 60 and K 120 combinations resulted in higher yields of fresh matter than in the combination without the potassium fertilizer (K 0). In the last year of the research, the additional CaSO4 fertilization resulted in the highest increase in the yield of the mixture of alfalfa and grasses, as compared with the variant without this fertilizer. The application of this fertilizer in the first years of the research also increased the yield of fresh matter.
A Realistic Approach to Calculating the Nitrogen Use Efficiency Index in Cereals with Winter Wheat (Triticum aestivum L.) as an Example
Nitrogen use efficiency (NUE) is a reliable index of nitrogen (N) management, given that it expresses the real relationships that exist between crop yield, its components, and the content of available N (Nmin) in the soil in the critical stages of yield formation. This article proposes a method for calculating NUE which is based on N input (Nin) into the soil/crop system in the critical phases of yield formation in winter wheat. For the validation of this hypothesis, a field experiment with WW in three subsequent growing seasons (2012/2013, 2013/2014, 2014/2015) was used. Treatments were arranged in a factorial distribution of two factors: (1) three rates of soil-applied magnesium (Mgs, 0, 25, 50 kg Mg ha−1); (2) foliar application of Mg to winter wheat (no application—control; double-stage Mg application in BBCH 30 and in 49/50). The dose of N fertilizer (Nf) was 190 kg ha−1. Two groups of N pools (soil Nmin and N mass in the wheat biomass) were determined in BBCH 30, 58, and 89. These core datasets were used to calculate total N input (Nin) to the soil/crop system during the two main periods of WW growth: (1) before (vegetative mega-phase, V) and (2) after wheat flowering (reproductive mega-phase, R, or grain filling period, GFP). The number of grains per ear (GE) and the number of grains per unit area (grain density: GD) depended significantly on Nin at the onset of flowering. A Nin58 of 517 kg N ha−1 resulted in a GD of 28.3 × 1000 grains m−2, producing 9.47 t grain ha−1. The NUE indices calculated in the V phase were the best predictors of GE and GY. The apparently low NUE index in this phase clearly indicates (i) the high potential of winter wheat for grain set per ear, (ii) consequently resulting in a strong depletion of N soil resources during the GFP. Therefore, the reduced NUE before winter wheat flowering is essential for the achievement of a high GD. The NUE feedback phenomenon as found in this study is a crucial condition for the effective depletion of the inorganic N pool during the grain filling period of winter wheat. It can be concluded that the NUE indices obtained in the V mega-phase actually describe the N economy in winter wheat production very well.
