Rice Fertilizer Research Articles

Potassium deficiency enhances imbalances in rice water relations under water deficit by decreasing leaf hydraulic conductance.

Potassium (K+) is an essential macronutrient for appropriate plant development and physiology. However, little is known about the mechanisms involved in the regulation of leaf water relations by K under water deficit. A pot experiment with two K supplies of 0.45 and 0 g K2O per pot (3 kg soil per pot) and two watering conditions (well-watered and water-deficit) was conducted to explore the effects of K deficiency on canopy transpiration characteristics, leaf water status, photosynthesis, and hydraulic traits in two rice genotypes with contrasting resistance to drought. The results showed that K deficiency reduced canopy transpiration rate by decreasing stomatal conductance, which led to higher canopy temperatures, resulting in limited water deficit tolerance in rice. In addition, K deficiency led to further substantial reductions in leaf relative water content and water potential under water deficit, which increased the imbalance in leaf water relations under water deficit. Notably, K deficiency limited leaf gas exchange by reducing leaf hydraulic conductance, but decreased the intrinsic water use efficiency under water deficit, especially for the drought-resistant cultivar. Further analysis of the underlying process of leaf hydraulic resistance revealed that the key limiting factor of leaf hydraulic conductance under K deficiency was the outside-xylem hydraulic conductance rather than the xylem hydraulic conductance. Overall, our results provide a comprehensive perspective for assessing leaf water relations under K deficiency, water deficit, and their combined stresses, which will be useful for optimal rice fertilization strategies.

Phosphate fertilization in sequeiro rice cropping

Rice farming has great importance in Brazil and around the world as the grain is a vital source of carbohydrates, proteins, vitamins and minerals. With an increasing productive demand, there is need to search for sustainable and more efficient means of production. A promising alternative is fertilization with organomineral fertilizers, however, its application and efficiency is little explored by the literature. The objective of the study was to evaluate the effect of varying doses of phosphorus (P) from organomineral fertilizer on the productivity and nutritional status of rice plants. The design was completely randomized with 3 replications. The rice plants were treated with doses of 0, 75, 150 and 225 kg/ha of P2O5 from organic-mineral fertilizer and doses of 75 and 150 kg/ha of P2O5 from high solubility mineral fertilizer. The macro and micronutrient contents of fresh grain mass, total dry grain mass, dry grain mass and mass of 100 grains of rice were evaluated. The organomineral phosphate fertilizer showed similar behaviour to the high-solubility mineral fertilizer.

Optimizing Nutrient Recommendations for Bottle Gourd Crop by Formulation of Targeted Yield Equations in an Inceptisol of Odisha, India

A field experiment was conducted to formulate targeted yield equations for bottle gourd under a rice-vegetable cropping system in an Inceptisol of Odisha. The experiment started with the creation of three soil fertility gradient stripes by applying no fertilizer, recommended dose and double the recommended dose of fertilizer in rice (cv. Lalat) during the kharif season. Each fertility gradient strip was divided into 24 sub-plots and superimposed with 21 different combinations of nutrients containing N, P, and K; FYM in two plots at 5t and 10t ha-1 and one plot was kept as absolute control following which, bottle gourd was grown during the rabi season. The highest yield (116.3q ha-1) of bottle gourd was achieved in S-III with an application of 70, 100, and 100 kg N, P2O5, and K2O per hectare, respectively. The nutrient requirement (NR) for producing one quintal of bottle gourd yield was 0.30, 0.20, and 0.30 kg N, P2O5 and K2O, respectively. The effect of graded doses of fertilizers on nutrient requirement, yield and nutrient uptake of bottle gourd were studied and subsequently, fertilizer prescription equations were derived for targeted yield of bottle gourd. A ready reckoner chart has also been prepared for facilitating farmers to achieve the desired yield target of bottle gourd by applying the required quantity of plant nutrients in the existing soil fertility level. The equations provide a basis for site-specific nutrient management based on desired yield targets under varying soil fertility conditions.

A reasoning method for rice fertilization strategy based on spatiotemporal knowledge graph

AbstractThe lack of multidimensional knowledge means that current reasoning methods for rice fertilization cannot make decisions accurate when faced with complex spatiotemporal conditions in general. Therefore, we propose a reasoning method for rice fertilization strategy based on spatiotemporal knowledge graph. First, we systematically organize multisource expert knowledge about rice fertilization, and construct an ontology for rice fertilization consisting of five core elements: rice variety, planting environment, nutrition diagnosis, fertilization schemes, and time and place. Spatiotemporal differences in rice fertilization knowledge are expressed by assessing spatiotemporal concepts, relations, and state instances. Second, we propose a reasoning method for rice fertilization strategy based on the constructed knowledge graph. This method leverages a certainty factor model for nutrition diagnosis and integrates case‐based and rule‐based reasoning to determine fertilization schemes for different stages. Finally, taking Pucheng County, China, as an example, knowledge from crowd‐sensing data is obtained to construct a knowledge graph using the proposed method. The results demonstrate the method can support the expression and complex reasoning of rice fertilization decisions under different spatiotemporal conditions.

OsALKBH9-mediated m6A demethylation regulates tapetal PCD and pollen exine accumulation in rice.

The N6-methyladenosine (m6A) mRNA modification is crucial for plant development and stress responses. In rice, the male sterility resulting from the deficiency of OsFIP37, a core component of m6A methyltransferase complex, emphasizes the significant role of m6A in male fertility. m6A is reversible and can be removed by m6A demethylases. However, whether mRNA m6A demethylase regulates male fertility in rice has remained unknown. Here, we identify the mRNA m6A demethylase OsALKBH9 and demonstrate its involvement in male fertility regulation. Knockout of OsALKBH9 causes male sterility, dependent on its m6A demethylation activity. Cytological analysis reveals defective tapetal programmed cell death (PCD) and excessive accumulation of microspores exine in Osalkbh9-1. Transcriptome analysis of anthers shows up-regulation of genes involved in tapetum development, sporopollenin synthesis, and transport pathways in Osalkbh9-1. Additionally, we demonstrate that OsALKBH9 demethylates the m6A modification in TDR and GAMYB transcripts, which affects the stability of these mRNAs and ultimately leads to excessive accumulation of pollen exine. Our findings highlight the precise control of mRNA m6A modification and reveal the pivotal roles played by OsALKBH9-mediated m6A demethylation in tapetal PCD and pollen exine accumulation in rice.

Field and simulation studies on yield, water and nitrogen dynamics and use efficiency in rice-wheat crops in sequence

ContextThe dominant rice-wheat cropping system in the Indo-Gangetic plain faces challenges of water depletion and nitrogen pollution of groundwater as well as declining productivity caused by over irrigation and nitrogen fertilization by the farmers. To appreciate the apt use of irrigation water and nitrogen fertilizer in rice and wheat crops it is essential to explore the water and nitrogen balances as well as dynamics in these crops, involving complex interaction between weather, soil, irrigation water and nitrogen fertilizer management. ObjectiveThe objective of the study is to quantify yield, field water balance components, water use efficiency, water productivity, water footprint, and water and nitrogen dynamics of rice and wheat crops in relation to season, varieties, irrigation regimes and nitrogen levels. MethodsField experimentations were conducted in double split plot design along with calibrated and validated HYDRUS 1D model use for two years comprising of treatments in rice i.e. two varieties (PR122-V1 and PR126-V2), two irrigation regimes (2-days drainage period-I1 and soil water suction 16 kPa-I2) and two nitrogen levels (120-N1 and 90-N2 kg N ha−1); and in wheat, two varieties (Unnat PBW343-V1 and Unnat PBW550-V2), two irrigation (1.2 IW/CPE-I1 and 0.9 IW/CPE-I2) regimes and two nitrogen levels (120-N1 and 90-N2 kg N ha−1). ResultsThe highest grain yield recorded was 7.6 t ha−1 in treatment combination of V1I2N1 in rice and 5.4 t ha−1 in V1I1N1 in wheat owing to better plant growth and yield attributes (biomass production, number of effective tillers, panicle length, and 1000 grain weight). Total water footprints were lower in the treatment combination of V1I1N1 in rice and V1I2N1 in wheat. The water budget revealed a higher percent contribution of the total water input to drainage (62 %) in rice ensuing restoration of water in the soil profile; and to evapotranspiration (ET) (100 %) in wheat ensuing water depletion. Modeling water and nitrogen dynamics showed higher root water uptake in I2 treatment in rice and with I1 treatment in wheat; and leaching losses of NO3-N under rice than wheat; and under I2 treatment than I1 as well as in N1 than N2. ConclusionsThe V1I2N1 treatment in rice and V1I1N1 treatment in wheat demonstrated superior grain yield, soil water storage, and root water uptake. Conversely, V1I1N1 treatment in rice and V1I2N1 treatment in wheat showed higher water use efficiency and lower water footprint. SignificanceIt helps to evaluate the effectiveness of irrigation and nitrogen management strategies in maximizing crop productivity while minimizing environmental impacts.

A timely death of the tapetum underlies MORE FLORET1 (MOF1) regulation of male fertility in rice.

A timely death of the tapetum underlies MORE FLORET1 (MOF1) regulation of male fertility in rice.

Rice transcription factor OsWRKY37 positively regulates flowering time and grain fertility under copper deficiency.

Efficient uptake, translocation, and distribution of Cu to rice (Oryza sativa) spikelets is crucial for flowering and yield production. However, the regulatory factors involved in this process remain unidentified. In this study, we isolated a WRKY transcription factor gene induced by Cu deficiency, OsWRKY37, and characterized its regulatory role in Cu uptake and transport in rice. OsWRKY37 was highly expressed in rice roots, nodes, leaf vascular bundles, and anthers. Overexpression of OsWRKY37 promoted the uptake and root-to-shoot translocation of Cu in rice under -Cu condition but not under +Cu condition. While mutation of OsWRKY37 significantly decreased Cu concentrations in the stamen, the root-to-shoot translocation and distribution ratio in brown rice affected pollen development, delayed flowering time, decreased fertility, and reduced grain yield under -Cu condition. yeast one-hybrid, transient co-expression and EMSAs, together with in situ RT-PCR and RT-qPCR analysis, showed that OsWRKY37 could directly bind to the upstream promoter region of OsCOPT6 (copper transporter) and OsYSL16 (yellow stripe-like protein) and positively activate their expression levels. Analyses of oscopt6 mutants further validated its important role in Cu uptake in rice. Our study demonstrated that OsWRKY37 acts as a positive regulator involved in the uptake, root-to-shoot translocation, and distribution of Cu through activating the expression of OsCOPT6 and OsYSL16, which is important for pollen development, flowering, fertility, and grain yield in rice under Cu deficient conditions. Our results provide a genetic strategy for improving rice yield under Cu deficient condition.

Rice yield in Costa Rican Central Pacific did not improve with a urease inhibitor

Urea is widely used as nitrogen (N) source for rice fertilization in Costa Rica, despite its low efficiency linked to ammonia losses. To assess urea management alternatives, two field experiments were conducted in the Central Pacific region of Costa Rica to study the effect of N-(n-butyl) thiophosphoric triamide (NBPT) on rice yield and N use efficiency (NUE). In Experiment 1 (Exp1) three tillage treatments (commercial-CT-, reduced-RT-, and reduced tillage with previous subsoiler-RTS-) were evaluated with three N managements: control (without N), urea at 124 kg N ha-1 with and without NBPT. In Experiment 2 (Exp2), a 100 kg N ha-1 rate (with and without NPBT) was evaluated along with a control (without N). NUE was estimated using 15N urea isotopic labeling technique for both trials. In Exp1, a significant difference of 4.8% in NUE for grain was observed among urea with and without NBPT, but no tillage effect was observed. No statistically significant differences were observed in yield among the fertilization treatments (Exp1: 3.56 ± 0.98 t ha-1 for urea and 3.85 ± 0.85 t ha-1 for urea with NBPT; Exp2: 3.38 ± 0.39 t ha-1 for urea and 3.40 ± 0.58 t ha-1 for urea with NBPT) or due to different tillage practices (CT: 3.33 ± 0.79 t ha-1, RT: 3.56 ± 0.74 t ha-1, and RTS: 4.23 ± 0.98 t ha-1). Although the NBPT is a viable option to reduce ammonia losses, its adoption in tropical conditions might be restricted by the small impact on yield.

The vesicle trafficking gene, OsRab7, is critical for pollen development and male fertility in cytoplasmic male-sterility rice

Rice cytoplasmic male sterility (CMS) provides an exceptional model for studying genetic interaction within plant nuclei given its inheritable trait of non-functional male gametophyte. Gaining a comprehensive understanding of the genes and pathways associated with the CMS mechanism is imperative for improving the vigor of hybrid rice agronomically, such as its productivity. Here, we observed a significant decrease in the expression of a gene named OsRab7 in the anther of the CMS line (SJA) compared to the maintainer line (SJB). OsRab7 is responsible for vesicle trafficking and loss function of OsRab7 significantly reduced pollen fertility and setting rate relative to the wild type. Meanwhile, over-expression of OsRab7 enhanced pollen fertility in the SJA line while a decrease in its expression in the SJB line led to the reduced pollen fertility. Premature tapetum and abnormal development of microspores were observed in the rab7 mutant. The expression of critical genes involved in tapetum development (OsMYB103, OsPTC1, OsEAT1 and OsAP25) and pollen development (OsMSP1, OsDTM1 and OsC4) decreased significantly in the anther of rab7 mutant. Reduced activities of the pDR5::GUS marker in the young panicle and anther of the rab7 mutant were also observed. Furthermore, the mRNA levels of genes involved in auxin biosynthesis (YUCCAs), auxin transport (PINs), auxin response factors (ARFs), and members of the IAA family (IAAs) were all downregulated in the rab7 mutant, indicating its impact on auxin signaling and distribution. In summary, these findings underscore the importance of OsRab7 in rice pollen development and its potential link to cytoplasmic male sterility.

Spikelets Fertility and Quality of Local Upland Rice (Oryza sativa L.) Seeds Due to High Temperature at Various Stages

Spikelets Fertility and Quality of Local Upland Rice (<i>Oryza sativa</i> L.) Seeds Due to High Temperature at Various Stages

Yield gap analysis and the relative importance of factors explaining yield variability in paddy fields

Closing the yield gap of strategic crops can facilitate achieving sustainable solutions to alleviate hunger, ensure food security, and enhance nutrition. This study aimed to quantify factors affecting rice yield gap in northern Iran using experimental and survey data on yields and management practices. The CERES-Rice model, calibrated with data (2011, 2016, 2019) from two regions, was used to estimate potential yield (Yp) of different rice cultivars. Yield gaps were calculated as the difference between economic yield potential and the average yield attained by farmers. The calibration process showed that cultivar coefficients varied across rice varieties. The simulated yields (2012–2021) showed that the mean potential yields were 13362 kg ha−1 and 8818 kg ha−1 for the late and early-maturing cultivars, respectively. High temperature was the most important yield defining factor across the rice growing areas. The yield gap was 3751 kg ha−1 and 2830 kg ha−1 in the late- and early-maturing cultivars, respectively. Nitrogen fertilizer rate, number of fertilizer applications, phosphorus fertilizer rate, transplanting date, potassium fertilizer rate, and seedling age were the top factors influencing the yield gap. Among the management factors, rice fertilizer management explained about 65% of the yield variability. Together, transplanting date and seedling age explained 15.3% of the variability in rice production, while pest, disease, and weed damage accounted for 9.6%. Breaking down the yield gap into affecting factors allows growers to improve the production system by providing the best crop management according to their facilities and capabilities. This approach is essential for optimizing agricultural productivity and achieving sustainable food production goals.

Integrated assessment of yield, nitrogen use efficiency and ecosystem economic benefits of use of controlled-release and common urea in ratoon rice production

Controlled-release urea (CRU) is commonly used to improve the crop yield and nitrogen use efficiency (NUE). However, few studies have investigated the effects of CRU in the ratoon rice system. Ratoon rice is the practice of obtaining a second harvest from tillers originating from the stubble of the previously harvested main crop. In this study, a 2-year field experiment using a randomized complete block design was conducted to determine the effects of CRU on the yield, NUE, and economic benefits of ratoon rice, including the main crop, to provide a theoretical basis for fertilization of ratoon rice. The experiment included four treatments: (i) no N fertilizer (CK); (ii) traditional practice with 5 applications of urea applied at different crop growth stages by surface broadcasting (FFP); (iii) one-time basal application of CRU (BF1); and (iv) one-time basal application of CRU combined with common urea (BF2). The BF1 and BF2 treatments significantly increased the main crop yield by 17.47 and 15.99% in 2019, and by 17.91 and 16.44% in 2020, respectively, compared with FFP treatment. The BF2 treatment achieved similar yield of the ratoon crop to the FFP treatment, whereas the BF1 treatment significantly increased the yield of the ratoon crop by 14.81% in 2019 and 12.21% in 2020 compared with the FFP treatment. The BF1 and BF2 treatments significantly improved the 2-year apparent N recovery efficiency, agronomic NUE, and partial factor productivity of applied N by 11.47–16.66, 27.31–44.49, and 9.23–15.60%, respectively, compared with FFP treatment. The BF1 and BF2 treatments reduced the chalky rice rate and chalkiness of main and ratoon crops relative to the FFP treatment. Furthermore, emergy analysis showed that the production efficiency of the BF treatments was higher than that of the FFP treatment. The BF treatments reduced labor input due to reduced fertilization times and improved the economic benefits of ratoon rice. Compared with the FFP treatment, the BF1 and BF2 treatments increased the net income by 14.21–16.87 and 23.76–25.96%, respectively. Overall, the one-time blending use of CRU and common urea should be encouraged to achieve high yield, high nitrogen use efficiency, and good quality of ratoon rice, which has low labor input and low apparent N loss.

Temperature and light reverse the fertility of rice P/TGMS line ostms19 via reactive oxygen species homeostasis.

P/TGMS (Photo/thermo-sensitive genic male sterile) lines are crucial resources for two-line hybrid rice breeding. Previous studies revealed that slow development is a general mechanism for sterility-fertility conversion of P/TGMS in Arabidopsis. However, the difference in P/TGMS genes between rice and Arabidopsis suggests the presence of a distinct P/TGMS mechanism in rice. In this study, we isolated a novel P/TGMS line, ostms19, which shows sterility under high-temperature conditions and fertility under low-temperature conditions. OsTMS19 encodes a novel pentatricopeptide repeat (PPR) protein essential for pollen formation, in which a point mutation GTA(Val) to GCA(Ala) leads to ostms19 P/TGMS phenotype. It is highly expressed in the tapetum and localized to mitochondria. Under high temperature or long-day photoperiod conditions, excessive ROS accumulation in ostms19 anthers during pollen mitosis disrupts gene expression and intine formation, causing male sterility. Conversely, under low temperature or short-day photoperiod conditions, ROS can be effectively scavenged in anthers, resulting in fertility restoration. This indicates that ROS homeostasis is critical for fertility conversion. This relationship between ROS homeostasis and fertility conversion has also been observed in other tested rice P/TGMS lines. Therefore, we propose that ROS homeostasis is a general mechanism for the sterility-fertility conversion of rice P/TGMS lines.

Increased panicle nitrogen application improves rice yield by alleviating high-temperature damage during panicle initiation to anther development.

The grain yield is closely associated with spikelet fertility in rice (Oryza sativa L.) under high temperatures, and nitrogen (N) plays a crucial role in yield formation. To investigate the effect of panicle N application on yield formation under high temperatures at the panicle initiation stage, two rice varieties [Liangyoupeijiu (LYPJ, heat susceptible) and Shanyou63 (SY63, heat tolerant)] were grown and exposed to high daytime temperature (HT) and control temperature (Control) during the panicle initiation stage. Low (LPN) and high (HPN) panicle N applications were conducted. HT markedly decreased the yields by 87% at LPN and 48% at HPN in LYPJ and 31% at LPN and 36% at HPN in SY63. The decrease in grain yield under HT was primarily attributed to the decline in spikelet fertility, HPN increased spikelet fertility. HT resulted in the abnormal development of anthers, which included disordered, enlarged, and broken anther wall layers, degraded and irregularly shaped microspores, delayed tapetum degradation, less vacuolated microspores per locule, abnormal and aborted pollen grains; however, HPN improved the development of anthers under HT, particularly in LYPJ. A high rate of evapotranspiration resulted in an approximately 1°C decrease in panicle temperatures at HPN compared with that at LPN in both varieties under HT. Overall, these results demonstrate that the increased panicle N application favors normal anther development in LYPJ by decreasing the panicle temperature, which results in high pollen viability and spikelet fertility, and consequently less yield loss under HT.

Effect of varied levels of Salvinia molesta vermicompost on soil fertility and crop productivity of rice under coastal conditions of Udupi, Karnataka

Effect of varied levels of Salvinia molesta vermicompost on soil fertility and crop productivity of rice under coastal conditions of Udupi, Karnataka

Evaluating the Potential of Fermented Leguminous Plant Leaves as a Fertilizer for Rice (Oryza Sativa) Production

Synthetic fertilizers improved rice yield, but they were expensive and reduced soil health. Fermented leguminous plant leaves (FLPL) were natural fertilizers that had a lot of nutrients that plants needed to grow and develop because they were locally available and economical to farmers. This study investigated the effects of fermented leguminous plant leaves as fertilizer for rice. The four treatments were arranged in a Randomized Complete Block Design and replicated three times. Plant height, tillers, grain weight, and economic returns were collected and analyzed using Analysis of Variance (ANOVA). The results showed that the control group that received synthetic fertilizers had significantly (P0.05) taller rice plants compared to the treatment groups. However, among the fermented leguminous leaves, rice plants that received Madre de cacao showed the highest plant height due to its high phosphorus content. The study also found no significant differences (P0.05) in the number of tillers between the treatments, indicating that fermented leguminous leaves can provide the necessary nutrients for crop growth. It was concluded that fermented leguminous leaves can be used as fertilizer to promote eco-friendly rice farming practices. Madre de cacao leaves were recommended as organic fertilizer for rice for at least three months to enhance plant height and overall plant growth. The potential of FLPL, especially from madre de cacao, as an economical alternative to synthetic fertilizers is a breakthrough in rice production. The results demonstrated the potential benefits of using Madre de Cacao leaves as fertilizer to promote eco-friendly rice farming.

Lexicographic Ordering and Loss Aversion among Low-Income Farmers

As Richard Day explained, expected utility theory suffers from procedural irrationality. This and other problems are illustrated here in the context of decision-making among low-income farmers. Farmers in developing countries are commonly thought to underinvest in modern techniques because their low incomes make them especially risk averse. In addition to the procedural leap of faith, highly restrictive assumptions are needed to apply expected utility theory to the problem. Nor does expected utility theory, as usually prescribed, fit the narrative of loss aversion. The reader is introduced to a procedurally rational substitute called lexicographic safety first. The model is illustrated for the case of rice fertilization in the Philippines, and policy implications are drawn. To illustrate the potential appeal of lexicographic ordering for other applications involving thresholds, a lexicographic model of rational addiction is also provided.

Effects of different fertilization patterns on the dietary composition of Procambarus clarkii in a rice-crayfish coculture system

As an omnivorous species, crayfish (Procambarus clarkii) have varying feeding habits in different environments. However, little is known about the diet of crayfish under different fertilization patterns in rice-crayfish cocultures. In this study, we investigated the effect of fertilization on the growth performance, dietary composition and isotopic niche of crayfish in a rice-crayfish coculture system. Four experimental treatments were established: no fertilizer (CK), slow-release fertilizer (HS), crayfish rice fertilizer (XD) and compound fertilizer (FH). The results showed that HS and FH could significantly promote crayfish growth, and the growth of crayfish treated with HS was the best. Fertilization patterns had significant effects on the dietary composition of crayfish. The food source of unfertilized crayfish was relatively balanced. However, in the HS, XD and FH treatments, particulate organic matter increased with contribution rates of 34.04%, 56.89% and 42.86%, respectively. In addition, the artificial feed intake of crayfish in the FH group was the lowest. The isotopic niche revealed that crayfish in the HS group significantly increased in the direction of the δ15N axis. Based on routine economic indicators, slow-release fertilizer was suitable for the rice-crayfish coculture system. These findings could provide scientific guidance for the selection of fertilization modes in rice-crayfish coculture systems and the exploration of healthy crayfish culture models.

Modeling of The Nitrogen Requirement of Winter Wheat for Protein Content Using Optical Sensor in Central Anatolia Region of Türkiye

Chlorophyll meters manage both the amount and duration of nitrogen fertilizer application based on the principle that the chlorophyll or nitrogen content of plants should be maintained throughout their development. For smallholders in developing countries, the use of a hand-held meter to manage nitrogen fertilizer in rice and wheat is the most popular method. The adoption of nitrogen management strategies based on close sensing using chlorophyll meters and optical sensors will largely depend on the inclusion of specific economic analysis in future research. The importance of using sensors and chlorophyll meters for nitrogen fertilizer management depends on how successful current practices have been. In this study, five different nitrogen rates (0, 80, 120, 160, 200 kg N ha-1) were applied to two different wheat varieties, and the effect of these different nitrogen rates on wheat protein content was investigated in a randomized block design. A quadratic polynomial model described the relationship between protein content and nitrogen rates.