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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.
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.
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.
Inorganic Fungicides (Phosphites) Instead of Organic Fungicides in Winter Wheat—Consequences for Nitrogen Fertilizer Productivity
Substitution of organic with inorganic fungicides (phosphites, Phi) does not change the efficiency of fertilizer nitrogen (Nf) in winter wheat. This hypothesis was tested in the 2016/2017 and 2017/2018 growing seasons. A two-factorial experiment with three phosphite variants (Cu–Phi, Mg–Phi, and Cu/Mg) and six plant protection methods (fungicides + Phi ⟶ reduced fungicide frequency + phosphite ⟶ phosphite). Grain yield decreased with increasing frequency of phosphites instead of fungicides. The decrease in yields was 3.6 t ha−1 in the favorable 2016/2017 and 1.1 t ha−1 in the dry 2017/2018. The primary reason for yield decrease in a given growing season was increased wheat infestation by pathogens. The direct cause was disturbances in the nitrogen status of wheat after flowering on treatments with a predominance of phosphites. The thousand grain weight (TGW) responded negatively to reduced fungicide application frequency. The critical stage in the assessment of pathogen pressure on wheat was the medium milk phase (BBCH 75). At this stage, indices of SPAD and leaf greenness together with indices of wheat infestation with pathogens allowed for a reliable prediction of both TGW and grain yield. It can be concluded that phosphites do not substitute organic fungicides in limiting pathogen pressure in winter wheat. Moreover, increased pressure of pathogens significantly reduces Nf productivity.
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.
Balanced Fertilization of Winter Wheat with Potassium and Magnesium—An Effective Way to Manage Fertilizer Nitrogen Sustainably
In agricultural practice, in addition to determining the nitrogen (Nf) dose, it is necessary to effectively control its effect on currently grown crops. Meeting these conditions requires not only the use of phosphorus (P) and potassium (K), but also nutrients such as magnesium (Mg) and sulfur (S). This hypothesis was verified in a single-factor field experiment with winter wheat (WW) carried out in the 2015/2016, 2016/2017, and 2017/2018 growing seasons. The experiment consisted of seven variants: absolute control (AC), NP, NPK-MOP (K as Muriate of Potash), NPK-MOP+Ki (Kieserite), NPK-KK (K as Korn–Kali), NPK-KK+Ki, and NPK-KK+Ki+ES (Epsom Salt). The use of K as MOP increased grain yield (GY) by 6.3% compared to NP. In the NPK-KK variant, GY was 13% (+0.84 t ha−1) higher compared to NP. Moreover, GYs in this fertilization variant (FV) were stable over the years (coefficient of variation, CV = 9.4%). In NPK-KK+Ki+ES, the yield increase was the highest and mounted to 17.2% compared to NP, but the variability over the years was also the highest (CV ≈ 20%). The amount of N in grain N (GN) increased progressively from 4% for NPK-MOP to 15% for NPK-KK and 25% for NPK-KK+Ki+ES in comparison to NP. The nitrogen harvest index was highly stable, achieving 72.6 ± 3.1%. All analyzed NUE indices showed a significant response to FVs. The PFP-Nf (partial factor productivity of Nf) indices increased on NPK-MOP by 5.8%, NPK-KK by 12.9%, and NPK-KK+Ki+ES by 17.9% compared to NP. The corresponding Nf recovery of Nf in wheat grain was 47.2%, 55.9%, and 64.4%, but its total recovery by wheat (grain + straw) was 67%, 74.5%, and 87.2%, respectively. In terms of the theoretical and practical value of the tested indexes, two indices, namely, NUP (nitrogen unit productivity) and NUA (nitrogen unit accumulation), proved to be the most useful. From the farmer’s production strategy, FV with K applied in the form of Korn–Kali proved to be the most stable option due to high and stable yield, regardless of weather conditions. The increase in the number of nutritional factors optimizing the action of nitrogen in winter wheat caused the phenomenon known as the “scissors effect”. This phenomenon manifested itself in a progressive increase in nitrogen unit productivity (NUP) combined with a regressive trend in unit nitrogen accumulation (NUA) in the grain versus the balance of soil available Mg (Mgb). The studies clearly showed that obtaining grain that met the milling requirements was recorded only for NUA above 22 kg N t−1 grain. This was possible only with the most intensive Mg treatment (NPK-KK+Ki and NPK-KK+Ki+ES). The study clearly showed that three of the six FVs fully met the three basic conditions for sustainable crop production: (i) stabilization and even an increase in grain yield; (ii) a decrease in the mass of inorganic N in the soil at harvest, potentially susceptible to leaching; and (iii) stabilization of the soil fertility of P, K, and Mg.
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) [...]
Phosphorus HotSpots in Crop Plants Production on the Farm - Mitigating Critical Factors
Phosphorus resources, both in phosphate rocks and in the soil, are limited. However, effective food production is not possible without the use of P fertilizers. Recognizing and eliminating or at least ameliorating factors (hot spots) that interfere with the uptake and use of phosphorus (P) by crop plants is of key importance for effective use of both P and nitrogen (N) on the farm. Plants have developed many adaptation mechanisms to their environment, i.e., soil low in available phosphorus. The most important ones include the secretion of organic compounds into the rhizosphere and the association of plant roots with microorganisms. A classic example is mycorrhiza. These mechanisms can be used by the farmer to sequentially select plants in the crop rotation. The uptake of inorganic P (Pi) by plants from the soil is reduced by environmental (temperature and water) and soil factors (low content of available phosphorus, soil acidity, soil compaction). These factors are responsible for the growth and size of the root system. Mitigating these negative effects improves the efficiency of phosphorus uptake from the soil. The second group of critical factors, limiting both root growth and availability of phosphorus, can be effectively controlled using simple measures (for example, lime). Knowing this, the farmer must first control the level of soil fertility in the plant’s effective rooting zone and not only in the topsoil. Secondly, the farmer must multiply the productivity of applied mineral fertilizers used through targeted recycling: crop rotation, crop residues, and manure.
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.
Deficiencies of Secondary Nutrients in Crop Plants-A Real Challenge to Improve Nitrogen Management
Secondary nutrient (e.g., calcium, magnesium, sulfur) deficiencies in crop plants disturb the nitrogen balance in the plants, thus reducing the overall yield. This hypothesis was analyzed based on the physiological functions of these nutrients, in relation to the uptake and utilization of N, in crop plants. Nitrogen uptake by plants requires a well-developed root system, the size of which depends on the supply of calcium. This process is largely controlled by the content of toxic aluminum in the soil, which can be mitigated through the application of lime and/or gypsum. In humid climates, the excessive uptake of calcium by plants occurs during water shortages; this process significantly interferes with N uptake. Magnesium, which affects plant growth throughout the growing season, can effectively control excessive calcium uptake. Magnesium deficiency can be ameliorated with soil- or foliar-applied fertilizers. These stages define the timing of plant sampling and determination of the N:S ratio, as an indicator of plant nutritional status. The application of Mg, S, or MgS facilitates higher productivity of fertilizer N by narrowing the N:Mg and N:S ratios in plants. The use of secondary nutrients can allow farmers to obtain high yields while reducing both production costs and environmental risks.
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 [...]