Agronomic Assessment of Nitrogen Use Efficiency in Spring Wheat and Interrelations with Leaf Greenness Under Field Conditions

Four spring wheat genotypes (Triticum aestivum L.) were grown without (N0 = 0 kg N ha^?1) and under ample (N1 = 250 kg ha^?1) nitrogen (N) fertilizer in field experiments in two seasons. The aim was to assess genotypic variation in N use efficiency (NUE) components and N-related indices during grain filling thus to identify superior wheat genotypes. Leaf chlorophyll (SPAD) readings at crucial growth stages were employed to help differentiate genotypes. Interrelations between yield and N-related indices with SPAD, where also assessed to explain possible pathways of improving NUE early in the growing season. Results showed that genotypic effects on NUE were mostly evident in 2000, a year with drier preanthesis and wetter postanthesis than the normal periods. ‘Toronit’ almost always had the highest biomass yield (BY) and grain yield (GY). Except in 1999 under N0, ‘L94491? showed the highest % grain N concentration (GNC). Genotypes affected SPAD at almost all stages and N fertilization delayed leaf senescence for all genotypes and growth seasons. Correlations between SPAD at different growth stages and GY, N biomass yield at maturity (NBYM) and GNC were significant (P≤ 0.001), positive and strong/very strong (>r = 0.7). N translocation efficiency (NTE) was inversely related to PANU (~r = ? 0.77, P≤ 0.001), suggesting that N after anthesis is being preferentially transported to the ears to meet the N demand of the growing grains. It is concluded that there is still a large potential for increased NUE by improved N recirculation, use of fast and inexpensive crop N monitoring tools and high yielding, N uptake efficient genotypes.

Abbreviations: NUE, Nitrogen use efficiency; SPAD, Minolta SPAD-502 chlorophyll meter, NHI, nitrogen harvest index; HI, Harvest index; NTE, N translocation efficiency from vegetative plant parts to grain; DMTE, dry matter translocation efficiency; CPAY, contribution of pre-anthesis assimilates to yield; PANU, Post-anthesis N uptake, d.a.s., days after sowing, N0, zero (0) kg ha^?1 applied N fertilizer, N1, 250 kg ha^?1 applied N fertilizer.     

Grain yield,growth response,and water use efficiency of direct wet-seeded rice as affected by nitrogen rates under alternate wetting and drying irrigation system

ABSTRACT

The present investigation aimed to determine the effectiveness of different nitrogen (N) rates on grain yield, growth, and water use efficiencies of direct wet-seeded rice and to create a relationship of N rates with growth parameters and dry matter production at different stages. The experiments compared six rates of nitrogen (0, 40,80,120,160, and 200 kg ha^–1N) replicated thrice in randomized complete block design in two conjunctive years of 2009–2010 and 2010–2011 at Bangladesh Rice Research Institute farm, Gazipur.The highest grain yield of 7.85 and 7.22 t ha^?1 was observed in N₂₀₀ treatment in 2009–2010 and 2010–2011, respectively. The relationship (R²) of total dry matter with leaf area index , leaf area duration, and crop growth rate indicated strong association during booting stage to achieved maximum dry matter during harvest. Water use efficiency varied 87–91% in different N levels.     

Zinc and amino acids on wheat-soybean intercropping under no-till management

Abstract

Foliar fertilization with micronutrients and amino acids (AAs) has been used to increase the grain yield and quality of different crops. The aim of the present study was to evaluate the effects of Zn and AAs foliar application on physiological parameters, nutritional status, yield components and grain yield of wheat-soybean intercropping under a no-till management. We used a randomized block experimental design consisting of eight treatments and four replicates. The treatments were five Zn rates (0, 1, 2, 4 and 8?kg ha^?1) and 2?L ha^?1 of AAs and three additional treatments: a control (without the Zn or AA application), 2?kg ha^?1 Zn and 2?kg ha^?1 Zn + 1?L AA. The treatments were applied by spraying during the final elongation stage and at the beginning of pre-earing for the wheat and in growth stage V6 for the soybean for two crop years in a Typic Oxisol (860?g kg^?1 clay). Zinc foliar fertilization increased the wheat grain Zn concentrations. The Zn rates and AA foliar fertilization in soil with did not affect the physiological parameters, nutrient status or yield components. The AA application at the different concentrations tested changed the soybean grain yield and the leaf N concentration. The results suggest that Zn and amino acids application increases the grains Zn concentration in the wheat, being an important strategy to agronomic biofortification.     

Contribution of Biofertilizers and Fertilizer Nitrogen to Nutrient Uptake and Yield of Egyptian Winter Wheat

ABSTRACT

Nutrient uptake and grain and straw yield of Egyptian winter wheat (Triticum aestivum L. Merr.) were evaluated for two site-years after the seed inoculation with two biofertilizer products, Phosphorien, containing the phosphorus (P)-solubilizing bacteria Bacillus megatherium, and Nitrobien, containing a combination of nitrogen (N)-fixing bacteria Azotobacter chroococcum and Azospirillum liposerum. Ammonium nitrate and polymer-coated urea fertilizers were applied to plots alone and together with the biofertilizers at rates of either 83 kg N ha^?1 or 186 kg N ha^?1 for comparison. The highest grain yield (5.76–6.74 Mg ha^?1) and straw yield (11.49–13.32 Mg ha^?1) occurred at the highest fertilizer rates with N fertilizer. There was a slight additional increase in grain and straw yields when a biofertilizer was applied along with N fertilizer. A slightly higher grain and straw yield was measured with the polymer-coated urea treatment than with the ammonium nitrate treatment. The biofertilizer materials were not as effective as N fertilizers in producing grain (4.02–4.09 Mg ha^?1) or straw (7.71–8.11 Mg ha^?1) for either year, although the Nitrobien + Phosphorien combination increased these parameters over the N-fertilizer control. The effect of the Nitrobien biofertilizer in increasing grain yields was equivalent to a urea application rate of about 13 kg N ha^?1. Biofertilizer inoculations increased iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) concentrations in wheat tissue (at boot stage), but these higher levels did not influence grain or straw yield.     

Dry matter and nitrogen accumulation and remobilization in wheat as affected by genotype and irrigation

To investigate the genotypic differences of dry matter (DM) and nitrogen (N) accumulation and remobilization as well as the photosynthetic characteristics of flag leaf during grain filling under water-limited conditions, nine winter wheat cultivars were planted under two irrigation treatments including W0 (no irrigation applied during spring) and W2 (1500 m³ ha^?1 applied 50% at stem elongation and 50% at anthesis). Results showed that cultivar and irrigation significantly affected the accumulation and remobilization of DM and N as well as the photosynthetic characteristics of flag leaf. No irrigation in spring on average decreased the photosynthetic rate of flag leaf, accelerated leaf senescence, and consequently decreased the accumulation of DM and N, but increased the ear distribution ratio and the remobilization and contribution of DM and N in leaf and stem to grain. Maintaining high photosynthetic activity and promoting DM and N distribution in ear and the remobilization of DM and N in leaf and stem may lead to higher grain filling rate and lower yield loss under water-limited conditions in North China Plain.     

Mid-Season Prediction of Wheat-Grain Yield Potential Using Plant,Soil, and Sensor Measurements

ABSTRACT

The components that define cereal-grain yield potential have not been well defined. The objective of this study was to collect many differing biological measurements from a long-term winter wheat (Triticum aestivum L.) study in an attempt to better define yield potential. Four treatments were sampled that annually received 0, 45, 90, and 135 kg N ha^?1 at fixed rates of phosphorus (P) (30 kg ha^?1) and potassium (K) (37 kg ha^?1). Mid-season measurements of leaf color, chlorophyll, normalized difference vegetative index (NDVI), plant height, canopy temperature, tiller density, plant density, soil moisture, soil NH₄-N, NO₃-N, organic carbon (C), total nitrogen (N), pH, and N mineralization potential were collected. In addition, soil texture and bulk density were determined to characterize each plot. Correlations and multiple linear-regression analyses were used to determine those variables that can predict final winter wheat grain yield. Both the correlation and regression analyses suggested mid-season NDVI, chlorophyll content, plant height, and total N uptake to be good predictors of final winter wheat grain yield.     

Nitrogen Application in Irrigated Rice Grown in Mediterranean Conditions: Effects on Grain Yield,Dry Matter Production,Nitrogen Uptake,and Nitrogen Use Efficiency

ABSTRACT

Field experiments were conducted in the major rice growing area of Chile to evaluate the effects of nitrogen (N) fertilization and site on grain yield and some yield components, dry matter production, N uptake, and N use efficiency in rice cultivar ‘Diamante’. Two sites (indicated as sites 1 and 2) and six N rates (0, 50, 100, 150, 200, and 300 kg N ha^?1) were compared. Nitrogen fertilization increased yield, panicle density, spikelet sterility, dry matter production, and N uptake at maturity. 90% of maximum yield was obtained with 200 kg N ha^?1 in site 1 (12,810 kg ha^?1) and with 100 kg N ha^?1 in site 2 (8,000 kg ha^?1). These differences were explained by lower panicle density, and the resulting lower dry matter production and N uptake in site 2. Nitrogen use efficiency for biomass and grain production, and grain yield per unit of grain N decreased with N fertilization. While, agronomic N use efficiency and N harvest index were not affected. All N use efficiency indices were significantly higher in site 1, except grain yield per unit of grain N. The observed variation in N use efficiency indices between sites would reflect site-specific differences in temperature and solar radiation, which in turn, determined yield potentials of each site. On the basis of these results, cultivar ‘Diamante’ would correspond to a high-N use efficiency genotype for grain yield.     

Phosphorus,potassium, chloride,and fungicide effects on wheat yield and leaf rust severity

Abstract

Plant nutrition and disease suppression are among the most important management tools for producers of hard red winter wheat (Triticum aestivum L.) in the central and southern Great Plains. This study was conducted to examine the effects of phosphorus (P) (0, 15, and 30 kg ha^?1) and potassium (K) (0, 37, and 74 kg ha^?1) fertilization, foliar fungicide application, and cultivar disease tolerance on wheat yield, yield components, and severity of leaf rust (Puccinia triticina Eriks.). Compared with no P, fertilizing with P increased yield by as much as 60% (>1.3 Mg ha^?1 increase). Yield of cultivars susceptible to leaf rust was nearly 0.6 Mg ha^?1 less without K than with K fertilization. Fungicide application resulted in mean yields of 4.8 Mg ha^?1 for both resistant and susceptible cultivars, however, yield of susceptible cultivars was suppressed more than yield of resistant ones without fungicide. Although P fertilization had a moderately suppressive effect on leaf rust, the increased yield was primarily due to production of about 50% more heads m^?2 apparently from more prolific tillering. Similarly, K fertilization appeared to reduce leaf rust severity and improve yield by increasing kernel weight, but this response may have been related partially to chloride (Cl) in the KCl fertilizer. Correlations suggested that improving dry matter production and N, P, and K uptakes at the boot stage by P and K fertilization can reduce leaf rust severity later in the growing season and increase wheat grain yield. These results indicate that especially P fertilization, but also K fertilization and fungicide application, are important management tools for reducing disease and increasing winter wheat yield.     

Dry Matter and Yield of Lowland Rice Genotypes as Influence by Nitrogen Fertilization

ABSTRACT

Rice is a staple food for more than 50% of the world's population and nitrogen (N) is one of the most yield limiting nutrients in lowland rice ecosystems. A field experiment was conducted for two consecutive years to evaluate dry matter production and grain yield of 12 lowland rice genotypes (BRS Jaçanã, CNAi 8860, BRS Fronteira, CNAi 8879, CNAi 8880, CNAi 8886, CNAi 8885, CNAi 8569, BRSGO Guará, BRS Alvorada, BRS Jaburu, and BRS Biguá) at five N rates (0, 50, 100, 150, and 200 kg ha^{? 1}). Genotypes showed significant variation in grain yield and shoot dry weight. Genotype BRSGO Guará was highest yielding, whereas genotype BRS Jaburu was lowest yielding and the remaining genotypes were intermediate in grain yielding potential. Grain yield and shoot dry weight were having significant quadratic increase with increasing N rates in the range of 0 to 200 kg ha^{? 1}. However, 90% of the maximum yield is often considered as an economical rate, which was 120 kg for shoot dry weight and 136 kg N ha^{? 1} for grain yield. Shoot dry matter was having significant positive quadratic association with grain yield across 12 genotypes.     

The content and quality of protein in winter wheat grains depending on sulphur fertilization

Abstract

On soils lacking in water-soluble sulphur, the sulphur fertilization of winter wheat, in general, increases the yields. There are not sufficient investigations about the influence of sulphur on the quality of yield. The objective of this work was to investigate the content and quality of protein in wheat grain depending on sulphur fertilization. The present study relies on field trials conducted on two different soils during 2004–2009. Sulphur was applied with NS-fertilizer Axan or Axan Super at the rate of S 10 or 13.6 kg ha^?1 accompanied by a nitrogen background of N 100 kg ha^?1. The rates of N- and NS-fertilizers were divided and applied at the beginning and at the end of tillering. At harvest, the grain samples from trial variants in four replications were taken, and the contents of crude protein, wet gluten, amino acids (lysine, threonine, cysteine, methionine) and gluten index in wheat grain were determined. Besides, the contents of amino acids were recalculated on their concentrations in protein. The protein and wet gluten contents in grain varied significantly depending on weather conditions of the trial years. On break-stony soil, sulphur increased the yield by 1.16 t ha^?1 on average, i.e. by 21.7%. With increasing yields the protein and wet gluten concentrations in grain decreased. Under the influence of sulphur, the gluten index increased significantly – from 58 to 74, i.e. by 27.6%. In 2004 and 2005, sulphur increased the cysteine and methionine content in wheat grain. Although sulphur application in many cases decreased the protein and wet gluten contents in wheat grain, it improved the biological quality of protein because the concentrations of above-mentioned amino acids recalculated on their concentrations in protein increased significantly. The sulphur application in pseudopodzolic soil had a weaker effect on the grain quality than in break-stony soil.     

Yields of wheat and soil carbon and nitrogen contents following long-term incorporation of barley straw and ryegrass catch crops

Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long‐term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha^?1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha^?1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch‐cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha^?1 after treatment with 8 and 12 t straw ha^?1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha^?1 after 8 and 12 t straw ha^?1. No grain yield increases were found after 4 t straw ha^?1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha^?1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long‐term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.     

Development of Critical Values for the Leaf Color Chart,SPAD and Fieldscout CM 1000 for Fixed Time Adjustable Nitrogen Management in Aromatic Hybrid Rice (Oryza sativa L.)

The nitrogen (N) requirement of hybrid rice is generally greater than in conventional rice varieties. Recommendations for N monitoring at regular intervals of 7–10 days through leaf greenness are available, but farmers are accustomed to apply fertilizer N at selected growth stages only. An inexpensive leaf color chart (LCC) and nondestructive chlorophyll meters were evaluated for site-specific N management strategy in world’s first aromatic rice hybrid PRH-10 at the Indian Agricultural Research Institute, New Delhi. Two field experiments were conducted on PRH-10 with four levels of N (0, 70, 140, and 210 kg ha^?1) during June–October of 2010 and 2011 to determine the LCC, soil–plant analysis development (SPAD), and Fieldscout CM 1000 (CM 1000) values for achieving economic optimum grain yield at three critical growth stages (tillering, panicle initiation, and flowering). Quadratic regression between N levels and grain yield were used to determine economic optimum grain yield (6427 kg ha^?1 in 2010 and 6399 kg ha^?1 in 2011) corresponding to optimum economical dose of 151 kg N ha^?1 (2010) and 144 kg N ha^?1 (2011). Nitrogen concentration in fully expanded youngest leaf correlated significantly (P < 0.01) and positively with LCC score, SPAD value, CM 1000 value, and total chlorophyll concentration at tillering, panicle initiation, and flowering for both years. The critical LCC score, SPAD, CM 1000 values, chlorophyll concentration, and leaf N concentration obtained were at tillering 4.4, 42.3, 285, and 2.16 mg g^?1 fresh weight and 3.29%; at panicle initiation 4.4, 43.0, 276, and 2.16 mg g^?1 fresh weight and 3.02%; and at flowering 4.5, 41.7, 270, and 2.05 mg g^?1 fresh weight and 2.83%, respectively. Corrective N application should be done when observed leaf N indicator values at a particular growth stage reach or go below the critical values.     

Functional traits associated with nitrogen use efficiency in wheat

The association between functional traits and nitrogen use efficiency (NUE) was investigated to assist the breeding of nitrogen (N) use-efficient bread wheat (Triticum aestivum ssp. aestivum) varieties. This study combined results from a climate chamber experiment involving 41 spring wheat varieties and a field experiment involving six winter and six spring wheat varieties grown with and without the application of mineral N fertiliser. The climate chamber experiment was analysed by partial least squares (PLS) regression, with several predictors and NUE as response, to identify traits related to NUE. Specific hypotheses were then tested in the field experiment. The PLS indicated six traits of particular importance for overall NUE: leaf chlorophyll (SPAD value) of the top leaf at stem elongation, grains ear^?1, ears pot^?1, straw biomass pot^?1, days between emergence and anthesis, and days between emergence and completed senescence. In the field experiment, the SPAD value of flag leaves of winter wheat around anthesis was positively correlated with NUE and total grain N, at both N levels. Fast development was positively correlated with high NUE and N uptake efficiency in spring wheat. Early senescence of the flag leaf was positively correlated with grain N concentration and negatively correlated with grain-specific N efficiency in winter wheat at low N fertilisation levels. The results indicate that high SPAD value of the top leaf might be a candidate trait that could be used in wheat breeding for improved NUE, while genetic variation in senescence could possibly be used to tailor varieties for different end-use quality when grown at low N. More studies are needed to validate these findings in other environments and for other genotypes.     

Winter Wheat Yield,Quality, and Nitrogen Removal Following Compost- or Manure-Fertilized Sugarbeet

To efficiently use nitrogen (N) while protecting water quality, one must know how a second-year crop, without further N fertilization, responds in years following a manure application. In an Idaho field study of winter wheat (Triticum aestivum L.) following organically fertilized sugarbeet (Beta vulgaris L.), we determined the residual (second-year) effects of fall-applied solid dairy manure, either stockpiled or composted, on wheat yield, biomass N, protein, and grain N removal. Along with a no-N control and urea (202 kg N ha^?1), first-year treatments included compost (218 and 435 kg estimated available N ha^?1) and manure (140 and 280 kg available N ha^?1). All materials were incorporated into a Greenleaf silt loam (Xeric Calciargid) at Parma in fall 2002 and 2003 prior to planting first-year sugarbeet. Second-year wheat grain yield was similar among urea and organic N sources that applied optimal amounts of plant-available N to the preceding year’s sugarbeet, thus revealing no measurable second-year advantage for organic over conventional N sources. Both organic amendments applied at high rates to the preceding year’s sugarbeet produced greater wheat yields (compost in 2004 and manure in 2005) than urea applied at optimal N rates. On average, second-year wheat biomass took up 49% of the inorganic N remaining in organically fertilized soil after sugarbeet harvest. Applying compost or manure at greater than optimum rates for sugarbeet may increase second-year wheat yield but increase N losses as well.

Abbreviations CNS, carbon–nitrogen–sulfur     

Tissue Nitrogen as a Base for Recommendations of Additional Nitrogen to Spring Wheat in Southern Finland

Abstract

Nitrogen (N) deficiency has become more common in the traditional wheat cultivation areas of southern Finland as yield potentials have increased. Based on data for the period studied (1968-88) a grain protein concentration below 11.2% in spring wheat (Triticun aestivum L.) is an indicator of N deficiency. The mean of maximum grain yield obtained was 4655 kg ha^?1 when grain protein concentration exceeded 11.2%. The estimation of plant tissue N content could be an effective diagnostic tool for identifying N status in the early growth stages of spring wheat. To address the feasibility of this test, the present study was conducted in 1990-91 to determine the critical plant tissue N concentrations of three plant parts at the early double-ridge stage (Stage 2), at the stage when stigmatic branches of the carpel begin to form (Stage 7) and at pollination (Stage 10). Nitrogen was applied at rates of 0 and 110 kg N ha^?1 as granular ammonium nitrate and granular slow-release-nitrogen fertilizers to establish a wide range of plant tissue N levels, grain yields and grain protein concentrations. Critical plant N levels were calculated for the different plant parts using the Cate-Nelson procedure. From this study it can be concluded that the critical N level recommended for Stage 2 is 43 g of N kg^?1 dry matter of the whole plant. Critical N levels recommended for Stage 7 are 28 g of N kg^?1 dry matter of the whole plant, 30 g of N kg^?1 of the leaves and 13 mg total N in dry matter. Critical N levels recommended for Stage 10 are 12 g of N kg^?1 of the whole plant, 23 g of N kg^?1 of the leaves and 15 mg total N in dry matter.     

Liming and Nitrogen Effects on Maize Yield and Nitrogen Use Efficiency

ABSTRACT

The study was aimed to determine the appropriate nitrogen (N) rate to combine with liming for enhanced maize yield and nitrogen use efficiency (NUE). Two maize varieties [Ikom White (IKW) and Obatanpa-98 (Oba-98)], two lime rates (0 kg ha^?1 and 500 kg ha^?1) and three N rates (0, 90 and 180 kg ha^?1) were used. The treatments were laid as a split-split plot in a randomized complete block design with three replications. The growth attributes, photosynthetically active radiation (PAR), harvest index, dry matter, and grain yield increased (P ≤ 0.05) with increases in N rates, especially in plots amended with lime. Oba-98 was better yielding (2.12 versus (vs) 1.88 t ha^?1) and absorbed more (P ≤ 0.05) radiation (442.06 vs 409.54 μmol m^?2s^?1) than IKW. The efficiency indices and partial factor productivity were best optimized at the 90 kg ha^?1 N rate with Oba-98 having higher values than IKW. Therefore, liming (500 kg ha^?1) plus N at 180 kg ha^?1produced the best yield of the hybrid maize, Oba-98.     

Economic and environmental optimization of nitrogen fertilizer recommendations for cereals in Norway

Abstract

Results of 240 annual N fertilizer trials in 1991–2007 in spring and winter cereals are presented. On average, spring barley and oat yields increased little beyond 120 kg N ha^?1 in fertilizer. Somewhat higher figures were found for spring and winter wheat. Regression equations for yield and N uptakes in grain and straw were derived, related to N fertilizer input and the yield level in individual trials (indicator of yield expectancy). These equations accounted for 90% of the variation in yield and 80% of that in N uptake. Quadratic N responses were significant in all cases, as were interactions between N responses and yield level. They were verified with data from 27 separate trials performed in 2008–2010. The yield equations were used to calculate economically optimum N fertilizer levels with varying ratios of product price to fertilizer cost at contrasting levels of yield. The optimum N fertilizer level for barley and oats was found to increase by 8.3 kg N ha^?1 per Mg increase in expected yield. The equivalent figure in wheat was 16.3 kg N ha^?1. Optimum N fertilizer levels decreased by 4.1 and 6.7 kg N ha^?1, for barley/oats and wheat respectively, per unit increase in the cost/price ratio. The equations for N uptake were used to calculate simple N balances between fertilizer input and removal in crop products. Large N surpluses were indicated at low levels of yield expectancy, but the surplus declined markedly with increasing yield level, despite greater N fertilizer inputs at high yield. Calculations made for national average yield levels in recent years showed N surpluses of 50–60 kg N ha^?1 when only grain is removed and 25–40 kg N ha^?1 when straw is removed also. Limiting N input to obtain zero balance reduces yields considerably at average levels of yield expectancy.     

Optimizing the Nitrogen Management Strategy for Winter Wheat in the North China Plain Using Rapid Soil and Plant Nitrogen Measurements

Excessive nitrogen (N) fertilizer with improper split-application in small-scale farming is widespread for reducing N use efficiency and polluting the environment. The objective of this study was to develop a strategy for providing winter wheat with twice-topdressing N by quickly measuring the soil and plant N status. During the period 2009–2011, a field experiment was conducted for winter wheat cultivar Zhongmai-175 in the North China Plain. The mineral N (Nmin) pool at a soil depth of 0–90 cm and topdressing N twice, as total N supply, was gradually increased from 0 to 420 kg N ha^–1 to mimic the farmers´ practices. Measurements with the Soil Plant Analysis Development (SPAD) meter were taken on the uppermost fully expanded leaf, and the SPAD index was expressed relative to SPAD readings of sufficiently fertilized plants. Grain yield exhibited linear-plus-plateau responses to total N supply with a significant difference between years, the r² ranged from 0.73 to 0.94. With a basal N application of 30 kg ha^–1, the soil Nmin at 0–90 cm supplemented by twice-topdressing N (1:1 ratio) at Zadoks growth stage (ZGS) 22–23 in early spring and ZGS 47–52 was required at 150–165 kg N ha^–1 to achieve a maximum grain yield of 3.9–5.3 t ha^–1. The SPAD index exhibited a strong exponential response to N supply irrespective of plant growth stage and year (r² = 0.95–0.97); the value of 0.94 was critical in denoting N deficiency from sufficiency status. The N topdressing at ZGS 47–52 could be precisely modified/estimated by the equation y = 161.7–218x^5.16, where x is the SPAD index. Since SPAD readings varied significantly from year to year, our study suggests that it might be difficult to precisely manage field N for winter wheat.     

Interactive Effect of Phosphorus and Nitrogen on Leaf Anthocyanins,Tissue Nutrient Concentrations,and Dry‐Matter Yield of Floralta Limpograss during Short Day Length

Abstract

A field trial was conducted during the short‐day period of 2004–2005 at Ona, Fl., to study the factorial effect of nitrogen (67, 90, and 134 kg N ha^?1) and phosphorus (0, 5, 10, 20, and 40 kg P ha^?1) rates on forage dry‐matter yield, quality, nutrient uptake, and leaf pigment concentration of limpograss (Hemarthria altissima). The N and P fertilizers were applied 45 days before each of two harvests. There was no interaction between N and P rates on any of the measured variables. Cool‐season forage yield increased curvilinearly from 137 to 350 kg ha^?1 in winter and 237 to 1389 kg ha^?1 in early spring, whereas crude protein (CP) concentration increased from 145 to 158 g kg^?1, as P was increased from 0 to 40 kg ha^?1, but yield and CP were not affected by N rate. There was a decreasing linear relationship between leaf concentration of anthocyanins and P rate of application such that forage obtained with 0 kg P ha^?1 had 61% more leaf anthocyanins and purple pigmentation than with 40 kg P ha^?1. There was no effect of N on anthocyanins content. It was concluded that increased level of leaf anthocyanins was due to the cumulative stress from cool weather and lower plant‐tissue P levels, which resulted in reduced growth and yield of limpograss. In cool weather, P played a critical role in controlling leaf purple pigmentation and forage yield.     

Nitrogen Application in Winter Wheat Grown in Mediterranean Conditions: Effects on Nitrogen Uptake,Utilization Efficiency,and Soil Nitrogen Deficit

ABSTRACT

Nitrogen (N) is one of the most growth restricting nutrients in cereal grain and represents one of the highest input costs in agricultural systems; therefore, environmental and economic considerations require the effective use of N fertilizer in plant production. This study was conducted for three years to better understand wheat plant response to optimize N fertilizer and how to reduce the risk of ground water pollution.

Two of the most important durum wheat cultivars in Southern Italy and four N fertilization levels (0, 60, 120, and 180 kg N ha^{? 1}, indicated as N0, N60, N120, and N180, respectively) were compared in this experiment. During plant growth, fresh and dry matter, plant nutritional state (SPAD readings and stem nitrate content), and N uptake were determined. At harvest, plant N content, N uptake, grain yield, yield components and quality were determined, allowing the calculation of the pre- and postanthesis N uptake and the N utilization efficiency indices. Furthermore, at the beginning and at the end of each year, soil mineral N was measured to calculate mineral N deficit in the soil.

The results indicated that the treatment with 120 kg N ha^{? 1} of fertilizer ensures a good balance between yield and N utilization. In fact, N180 and N120 showed similar yield (3.01 and 3.07 t ha^{? 1}, respectively) and protein content (13.7 and 13.5 %). Meanwhile, throughout the three-year experiment, N180 presented the highest final mineral N content in the soil at the end of the cropping cycles, increasing the amount of N available for leaching. The N120 treatment showed the same values of N utilization indices as compared to N180, indicating that further doses of N fertilizer did not increase wheat N utilization. Plant N status shows that it is possible to modify the N fertilization to reach its optimum level during plant growth, in accordance with variable weather conditions, and consequently the plants requirements. The mean treatments of the preanthesis N uptake were about 67.5% of the total N uptake, and it was significantly and positively correlated with wheat yield. On the contrary, the postanthesis N uptake showed positive correlation with grain protein content, confirming the importance of late N supply in grains quality. The variation of weather conditions affected winter wheat yield, quality, N utilization and plant N status, but any difference throughout years was found between N180 and N120, confirming that higher N rate did not influence wheat growth, yield, and N uptake.