Response of wheat cultivars to different soil nitrogen and moisture regimes: III. Leaf water content,conductance, and photosynthesis 1

Two greenhouse studies were conducted with contrasting patterns of soil water availability and nitrogen (N) supply to extend our knowledge of the combined effect of these environmental factors on cultivar response of wheat (Triticum aestivum L.). Several parameters of water relations and photosynthesis were measured. Results showed that at the beginning of stem elongation and before imposing water stress, the low N treatment decreased leaf conductance and carbon dioxide (CO₂) exchange rate (CER). This effect was more significant in the case of the cultivar Nesma than the other cultivars. Leaf conductance was a much better indicator of CER than chlorophyll content. Overall, water stress decreased leaf conductance. Under mild stress, Nesma and Merchouch 8 behaved similarly, but Nesma was more sensitive to water stress. Increased N decreased CER under water stress but tended to have no effect on chlorophyll concentration. Under well watered conditions, N application helped the plants maintain greater leaf conductance, CER, and chlorophyll concentration than low N supply. Cultivar and N effects on relative water content (RWC) were not significant. Under severe water stress, Nesma tended to keep its stomata more open under N stress, while stomata of Merchouch 8 were not sensitive to N level variation. High N decreased leaf RWC of Nesma and Merchouch 8 but had no effect on Saada. From this study we concluded that under non‐water stressed conditions, added N increased leaf water conductance, CER, and chlorophyll. Under water stress, the cultivars responded differently to N application. High N decreased leaf conductance and relative water content. These results indicated that careful cultivar selection can complement good N management of wheat in areas prone to soil moisture stress.     

Response of wheat cultivars to different soil nitrogen and moisture regimes: II. Nitrogen up‐take,partitioning and influx 1

Nitrogen (N) is one of the major mineral nutrients required for growth and development of plants. Soil water availability, N concentration at the root surface and the ability of plants to absorb N are the most important factors that affect N uptake and partitioning. The objective of this study was to use greenhouse and growth chamber environments to investigate how two contrasting water regimes (stress and nonstress) and different soil N concentrations affect the uptake and distribution of N among different plant parts of three cultivars of wheat (Triticum aestivum L.) at different stages of development Results showed that at the beginning of stem elongation and under non N limiting conditions, there was a high and positive correlation between shoot dry matter production and shoot N content. Under N deficient soils that received different N rates, shoot N content was more related to shoot N concentration than to dry matter. Root growth and N content of the ‘Saada’ cultivar were negatively affected by high soil N concentration. Under mild water stress or nonstressed conditions, N uptake by the shoot increased with increased soil N in all cultivars. Overall, severe water stress masked the effect of N supply, and decreased N uptake in the case of ‘Merchouch 8’ and ‘Saada’. Root N content was not affected by water stress but increased when N was supplied. At anthesis and after rewatering plants from boot stage to anthesis, the plants fully recovered, and those that were water stressed, increased their N absorption to a rate much higher than those that were stressed. Nitrogen influx (NI) decreased with water stress, but increased more with increased soil N under well watered conditions than under stress. “Merchouch 8’ had higher NI than ‘Saada’. From this study we can conclude that the effect of N supply on N content was masked by severe water stress, and ‘Nesma’ was less sensitive to this stress. At anthesis, plants that were previously water stressed increased their rate of N uptake during the recovery. Root N was not affected by water stress but increased when soil N was increased.     

Seedling vigor and nitrogen use efficiency of Moroccan wheat as influenced by level of soil nitrogen

Abstract

One of the characteristics that can help wheat (Triticum aestivum L.) plants escape late season drought in the semiarid areas of Morocco is early stand establishment and adequate vigor. Little is known about the effect of nitrogen (N) on early seedling vigor in wheat. The objective of this study was to determine how N supply affects early root and shoot growth, N partitioning between the two parts and N use efficiency of seedlings. To reach this objective, three spring wheat cultivars were grown in pots in a growth chamber under N conditions which were low, adequate and high. Data showed that optimum N rates increased shoot and root growth but high N concentrations reduced their dry matter accumulation and inhibited root elongation. The cultivars tested behaved differently. ‘Nesma’, an older cultivar, produced 60% more dry matter and accumulated 93% more N in the shoot and root than the newer cultivars ‘Merchouch 8’ and ‘Saada’. Because of its high N uptake, ‘Nesma’ probably reduced soil N concentration at the root zone and avoided the negative effect of high N concentration on root growth. Although, ‘Nesma’ performed better and produced more dry matter, it used N less efficiently than the other two cultivars.

From this study, we can conclude that use of optimum N rates at time of seeing will result in quicker establishment and higher vigor of wheat seedlings. However, excessive N supply may retard seedling growth. The cultivars that produce more seedling dry matter with greater N accumulation are not necessarily the ones that use N more efficiently.     

Carbon dioxide assimilation efficiency of maize leaves under nitrogen stress at different stages of plant development

Abstract

Sub‐optimal nitrogen (N) affects the N‐rich carbon dioxide (CO₂) assimilation enzymes which can limit maize (Zea mays) production. The status of the carboxylation system is closely correlated to the Assimilation Efficiency Index (AEI) which is the initial slope of the CO₂ assimilation rate versus intercellular leaf CO₂ concentrations. Experiments were undertaken to ascertain the effect of soil N nutrition on the AEI, determine genotypic variability for AEI under N‐deficiency, determine how leaf and plant development affect treatment differences, and examine correlations between the AEI and plant development. Studies were conducted in the field and greenhouse on five maize genotypes on leaves of different ages at three stages of plant development. Field studies were conducted on a fine, silty mixed, mesic cumulic Hapludoll (1.2 g N kg^‐1), and high and low N treatments were imposed in the greenhouse. Quantum yield of emerging and mature leaves was determined. Results indicated that emerging and fully mature leaves had the greatest AEI values compared to other expanding leaves. Low N availability reduced the AEI of younger leaves but increased the AEI on the oldest leaf. The AEI increased until tasseling and then declined. Correlations were established between the AEI and leaf N concentrations and with CO₂ assimilation. Grain yield was correlated to the AEI during grain fill. Quantum yield of the mature leaf was greater with low N than with high N availability indicating that the energy capture or transfer mechanism was less affected by N levels than was the CO₂ trapping mechanism. There were pronounced gsnotypic differences in the AEI at tassel emergence but not in leaf N concentrations intimating differences in the distribution of N to enzymes and other compounds important for CO₂ assimilation. Internal N distribution was also dependent upon available N. The study demonstrated that the ability of a plant to maintain high carboxylation activity under N stress may be a valuable selection criteria for obtaining tolerance of corn to low soil N.     

Nitrogen and fungicide effects on winter wheat produced in the Louisiana Gulf Coast region

Management decisions affecting wheat (Triticum aestivum L.) yield include nitrogen (N) fertility rate, cultivar selection, and fungicide application. Since these cultural practices may interact with each other and the environment, often times affecting grain yield, test weight, and disease development, they need to be better defined for wheat production in for the Gulf Coast region. Field experiments were conducted to evaluate the effect of N rate, fungicide, and cultivar on grain yield, test weight, and disease development. Three N rates (67, 101, and 134 kg#lbha^‐1), two fungicide treatments (no‐fungicide control and fungicide), and four high‐yielding wheat cultivars with different levels of resistance to leaf rust (Puccinia recondite Rob. ex f. sp. tritici) were evaluated in 12 Louisiana field environments. Environment and interaction between environment and N rate, fungicide, and cultivar were significant for grain yield, leaf rust ratings, and test weight. Grain yield response to N rate was linear in five environments and quadratic in five environments. Although there was little evidence of a N x fungicide interaction for grain yield, increasing N rates increased leaf rust severity. Grain yields were increased by fungicide application in only four of twelve environments with a significant cultivar x fungicide interaction for grain yield. Grain yield increase from foliar fungicides was related to leaf rust severity and resistance of cultivars to leaf rust. Test weight was increased due to N in three environments and decreased in two environments. Test weight increased with fungicide application and varied among cultivars. The findings indicate that 101 kg N ha is probably adequate for maximum yield in most years. Although the higher N rates may increase yield in some years, disease pressure and the need for fungicides may also be increased.     

Response of wheat cultivars to different soil nitrogen and moisture regimes: I. Dry matter partitioning and root growth 1

The balance between root and shoot growth is one of the mechanisms used by plants to adapt to a particular environment. This balance is affected by nutrient supply and water availability. The objective of this study was to understand how nitrogen (N) affects root and shoot growth of three cultivars of wheat (Triticum aestivum L.) grown under two regimes of soil moisture ('non water stressed’ and ‘stressed’ during stem elongation') in the greenhouse and growth chamber. Data showed that before stem elongation, shoot growth was less sensitive to high soil N levels than root growth. In fact, root growth was inhibited by excessive soil N concentration. The cultivar ‘Nesma’ produced more dry matter, absorbed N more rapidly and avoided the negative effect of high soil N concentrations on root growth. ‘Merchouch 8’ produced less dry matter and tolerated more water stress, and appeared to require less water. Severe water stress masked the effect of N on root and shoot growth, and the negative effect of water stress on growth was more important under high N. Plants which were water stressed during stem elongation could not fully recover when they were rewatered from boot stage to anthesis. Nitrogen application improved shoot but not root growth under this soil moisture situation. This study suggested that shoot and root growth were affected differently by N availability and that high soil N levels enhanced the negative effect of water stress on growth.     

Sulfur Use Efficiency in Soybean Cultivars Adapted to Tropical and Subtropical Conditions

Sulfur (S) is an essential nutrient in crop plants and one of the components of amino acids (AAs) and proteins. Studies about sulfur efficiency on soybean cultivars [Glycine max (L) Merril] adapted to the tropical and subtropical conditions are still incipient. In Brazil, one experiment under greenhouse conditions evaluated the S-efficiency from eight soybean cultivars. The plants cultivated in a Typic Quartzipsamment received two S rates (0 and 80 mg kg^?1). The grain yield (GY), shoot dry weight (SDW), and the relative yield (RY) had influence from the S rates. The cultivars BRS 295RR and BRS 360RR were the most efficient in using the S application. The number of pods per plant (NPP), photosynthetic rate (A), nitrate reductase (N-NO₂^?), and chlorophyll significantly increased with de 80 mg kg^?1 of S. By contrast, the internal concentration of carbon dioxide (CO₂) (Ci) was reduced. Similarly, there were increases in the concentration of nitrogen (N), phosphorus (P), magnesium (Mg), and N:S ratio in the leaves and grain, but the K increased only in the leaves. Comparing the cultivars, only the N concentration in the leaves and the Mg in the grain had non-significant differences.     

Nitrogen and phosphorus requirements of different wheat plant types under dryland and irrigated conditions 1

The wheat (Triticum aestivum L.) plant type in major producing areas of the U.S. is changing rapidly from tall cultivars to high‐yielding semidwarf cultivars. Objectives of experiments were to determine if nitrogen and phosphorus nutritional requirements differ between traditional tall cultivars and modern semidwarf cultivars under dryland and irrigated conditions. ‘Larned’, a tall cultivar; ‘Newton’, a semidwarf cultivar; and ‘Plainsman V, a high‐protein semidwarf cultivar, were grown with all combinations of three nitrogen fertilizer levels (0, 84, and 168 kg N/ha) and two phosphorus fertilizer levels (0 and 90 kg P₂O₅/ha) at Colby, Kansas for two years. Three levels of irrigation—dryland, limited irrigation, and full irrigation—were applied. Grain yields were highest with 84 kg N/ha under dryland and with 168 kg N/ha under irrigation. Phosphorus increased grain yield under dryland conditions one year, but had no effect under irrigated conditions. Cultivar X nutrition interactions from differential yield responses to fertility levels occurred under the dryland and limited irrigation regimes one year. Grain protein content was increased by nitrogen fertilization under all regimes both years and was decreased only by phosphorus fertilization under dryland conditions one year. Cultivar X nitrogen interactions for grain protein occurred under all irrigation regimes. We concluded that nutrient requirements do not differ between tall and semi dwarf wheat culti‐vars under any irrigation regime. Raising the recommended level of nutrients, particularly nitrogen, should be considered for all cultivars, both tall and semidwarf.     

Managing Nitrogen and Sulfur Fertilization for Improved Bread Wheat Quality in Humid Environments

A large proportion of the wheat (Triticum aestivum L.) milled and utilized by bakeries in the eastern United States is hard red winter wheat (HRWW). Potential for producing this higher value commodity in the eastern United States is dependent on availability of adapted HRWW cultivars that are competitive with soft red winter wheat (SRWW) cultivars and implementation of management systems to enhance end-use quality. The effects of late-season nitrogen (N) (0–45 kg of N/ha) applied at two growth stages (GS 45 and 54) and sulfur (S) (0–34 kg of S/ha) applied at GS 30 on grain, flour, and milling and breadbaking quality were evaluated. Three diverse wheat cultivars (Soissons, Heyne, and Renwood 3260) were studied in two to five environments. Application of S and late-season N had little effect on grain yield. But N consistently increased grain and flour protein as well as bread loaf volume. The magnitude and significance of response to N and S varied by location and cultivar. While S alone did not have a significant effect on grain protein, S availability was critical in obtaining increased grain protein. Breadbaking quality of HRWW cultivars produced in the eastern United States can be improved through implementation of nutrient management approaches that include late-season application of 34–45 kg of N/ha and addition of S, particularly on sandy soils where S availability in the subsoil is low.     

Grain yield and nitrogen use efficiency of various modern rice cultivars grown at different nitrogen levels

Field trials were conducted to study the responses of grain yield and nitrogen (N) use efficiency at five input rates (N₀, N_82.5, N₁₆₅, N_247.5, and N₃₃₀ kg ha^?1) in a set of nine of the most representative rice cultivars. Grain yields of rice across the nine cultivars were increased significantly by N level. All the cultivars contained a significant linear plus plateau or quadratic relationship between N levels and grain yields.The minimum yields (means of 2 years) at N₀, N_82.5, N₁₆₅, N_247.5, and N₃₃₀ level all occurred in No. 2 cultivar. Compared with the grain yield of No. 2 at different N levels, those of the maximum cultivars increased by 37.1 (No. 8), 39.1 (No. 7), 48.4 (No.3), 43.3 (No. 4), and 43.9% (No. 3), respectively. In 2011, the highest average apparent nitrogen recovery efficiency (ANRE) in grain of the 4 N levels occurred in No. 3 cultivar (45.9%), followed by No. 4, No. 6, and No. 1, and the highest average agronomic efficiency (AE) in grain of the 4 N levels occurred in No. 9 cultivar [29.0 kg (kg N)^?1], followed by No. 3, No. 1, and No. 4. For the second-season planting, the highest average ANRE occurred in No. 4 cultivar (28.4%), followed by No. 3, No. 5, and No. 6, and the highest average AE occurred in No. 5 cultivar [18.1 kg (kg N)^?1], followed by No. 4, No. 3, and No. 7. Overall, No. 3 and No. 4 cultivars were the ideal ones that not only increased the grain yield but also improved the N use efficiency.     

Tillering,nutrient accumulation,and yield of winter wheat as influenced by nitrogen form 1

When grown with mixtures of nitrate‐nitrogen (NO₃‐N) and ammonium‐nitrogen (NH₄‐N) (mixed N) spring wheat (Triticum aestivum L.) plants develop higher order tillers and produce more grain than when grown with only NO₃. Because similar work is lacking for winter wheat, the objective of this study was to examine the effect of N form on tillering, nutrient acquisition, partitioning, and yield of winter wheat. Plants of three cultivars were grown to maturity hydroponically with nutrient solutions containing N as either all NO₃, all NH₄, or an equal mixture of both forms. At maturity, plants were harvested; separated into shoots, roots, and grain; and each part analyzed for dry matter and chemical composition. While the three cultivars varied in all parameters, mixed N plants always produced more tillers (by a range of 16 to 35%), accumulated more N (28 to 61%), phosphorus (P) (22 to 80%), and potassium (K) (11 to 89%) and produced more grain (33 to 60%) than those grown with either form alone. Although mixed N‐induced yield increases were mainly the result of an increase in grain bearing tillers, there was cultivar specific variation in individual yield components (i.e., tiller number, kernels per tiller, and kernel weight) which responded to N form. The presence of NH₄ (either alone or in the mixed N treatment), increased the concentration of reduced N in the shoots, roots, and grain of all cultivars. The effect of NH₄ in either treatment on the concentrations of P and K was variable and depended on the cultivar and plant part. In most cases, partitioning of dry matter, P, and K to the root decreased when NH₄ was present, while partitioning of N was relatively unaffected. Changes in partitioning between the shoot and grain were affected by N treatment, but varied according to cultivar. Based on these data, the changes in partitioning induced by NH₄ and the additional macronutrient accumulation with mixed N are at least partially responsible for mixed‐N‐induced increases in tillering and yield of winter wheat.     

Nitrogen deficiency induced a decrease in grain yield related to photosynthetic characteristics,carbon–nitrogen balance and nitrogen use efficiency in proso millet (Panicum miliaceum L.)

ABSTRACT

Field experiments involving proso millet (Panicum miliaceum L.) cultivar under four nitrogen (N) levels (N0, N60, N105 and N150) were conducted in 2015 and 2016 to explore the decrease in grain yield under N deficiency related to the changes in leaf photosynthetic characteristics, carbon (C)–N balance and N use efficiency. Results showed that N deficiency decreased the net photosynthesis rate, stomatal conductance, transpiration rate and chlorophyll content and increased the intercellular CO₂ concentration of proso millet flag leaves from flowering to maturity. N deficiency negatively regulated the C–N balance and increased the C/N ratio by reducing the total N, soluble protein and soluble sugar contents, resulting in high starch content. N uptake and utilisation were significantly reduced because of less available N. Significantly positive correlations were observed between the grain yield and photosynthetic characteristics or N use efficiency, whereas a negative correlation was found between the grain yield and the C/N ratio. The yields generated by N0, N60 and N105 were lower than that of N150 in both years. The N fertiliser regression formulae developed in the study would provide useful information about the N fertiliser rate of proso millet.     

Assessment of nitrogen uptake and utilization in drought tolerant and Striga resistant tropical maize varieties

Maize (Zea mays L.) is an important food crop in the Guinea savannas of Nigeria. Despite its high production potential, drought, Striga hermonthica parasitsim, and poor soil fertility particularly nitrogen deficiency limit maize production in the savannas. Breeders at IITA have developed drought- and Striga-tolerant cultivars for testing, dissemination, and deployment in the region. Information on the response of these cultivars to N fertilization is, however, not available. This study evaluated grain yield, total N uptake (TNU), N uptake (NUPE), N utilization (NUTE), and N use efficiency (NUE) of selected maize cultivars along with a widely grown improved maize cultivar at two locations in the Guinea savannas of northern Nigeria. Maize grain yield increased with N application. The average grain yield of the maize cultivars was 76% higher at 30, 156% higher at 60, and 203% higher at 120 kg N ha^?1 than at 0 kg N ha^?1. This suggests that N is a limiting nutrient in the Nigerian savannas. Five drought-tolerant cultivars produced consistently higher yields when N was added at all levels. These cultivars had either high NUPE or NUTE confirming earlier reports that high N uptake or NUTE improves maize grain yield. The study also confirms earlier reports that maize cultivars that are selected for tolerance to drought are also efficient in uptake and use of N fertilizer. This means that these cultivars can be grown with application of less N fertilizer thereby reducing investment on fertilizers and reduction in environmental pollution.     

昼夜连续照射LED红蓝光对不同品种生菜生长和品质的影响

为探究生菜对全生长期连续光照的响应及品种差异性,在密闭式植物工厂内,以LED红蓝光为光源研究了水培条件下常规光照（12h/12h,NL）与连续光照（24h/0h,CL）对5种生菜生长和品质的影响。结果表明：与常规光照（NL）处理相比,连续光照（CL）处理显著提高了除“大卫”外其它4种生菜的地上部鲜重,其中“绿罗”生菜增加幅度最高。生长初期连续光照（CL）处理下5种生菜叶片叶绿素含量显著高于常规光照（NL）处理,但在生长后期,5种生菜两个处理下的叶绿素含量均无显著差异。与常规光照处理相比,连续光照处理显著提高了5种生菜可溶性糖、总酚和类黄酮含量,以及其中2种紫叶生菜的花青素含量。除“绿罗”外,其它4个品种连续光照处理下的抗坏血酸总量均略有或显著升高,其中主要提高了还原型抗坏血酸的含量,对脱氢抗坏血酸含量的影响不显著。总之,全生长期连续光照能显著提高生菜的产量,促进可溶性糖和抗氧化物质合成;5个品种生菜对连续光照的适应性存在差异,其中“绿罗”的适应性最强;全生长期连续光照运用于植物工厂生菜生产对提高产量和品质的潜力较大。     

小黑麦基因型与环境互作效应及产量稳定性分析

选用26个小黑麦品种(系),在西北高寒农牧交错区的不同试点和供水条件下,利用GGE双标图法研究了小黑麦基因型与环境互作效应以及稳产性.结果表明:在自然干旱条件下,小黑麦平均籽粒产量为1805.5 ks/hm2,较普通小麦对照增产54.6%;在灌水条件下,小黑麦平均产量为7196.1 kg/hm2,较对照增产67.2%....     

Assimilate and nitrogen remobilization of six-rowed and two-rowed winter barley under drought stress at different nitrogen fertilization

Field experiments were conducted to investigate the effects of irrigation regimes and N levels on assimilate remobilization of two barley cultivars (Yousef_six-rowed and Nimrouz_two-rowed) in 2011 and 2012. There were three levels of water regimes (full irrigation (I₁₀₀), 75% and 50% of I₁₀₀: I₇₅ and I₅₀, respectively) in 2011. Rain-fed treatment (I₀) was included in 2012. Three N levels (0, 60, and 120 kg ha^?1) were used. Grain yield and assimilate remobilization decreased by severe water stress (I₀), however, the reduction of them were intensified by N fertilizer application. The N remobilization was negatively affected by N fertilization and water stress. The two-rowed showed higher N remobilization (10.7%) and contribution of N remobilized to N content of grain (5.8%) than the six-rowed. The two-rowed cultivar showed significantly higher assimilate remobilization and grain yield than the six-rowed under I₅₀ (26.3% and 6.5%, respectively) and I₀ (48.7% and 17.1%, respectively), while the six-rowed had similar or higher performances in terms of these traits under I₁₀₀ and I₇₅. This study showed that optimizing irrigation and N rates (decrease N level with increasing water stress) and selection of the suitable cultivars (Nimrouz_two-rowed) might increase assimilate remobilization and consequently grain yield under drought stress conditions.     

Grain Yield,Quality, and Nutrient Concentrations of Feed,Food, and Malt Barley

Barley (Hordeum vulgare L.) is a cereal grown for animal feed, human consumption, and malting. Nutrient concentrations are important as they provide information regarding the dietary values of barley consumed by animals or human beings. In addition, grain nutrient removal may be useful for refining fertilizer recommendations. A study was conducted in 2015 and 2016 investigating the cultivar effects on grain yield, quality, and grain nutrient concentrations and removal under irrigated conditions for two-row barley cultivars. Adjunct and feed cultivars produced the highest yields compared with the all-malt and food cultivars. Specific quality and nutrient values were greater than or equal to in the food cultivar compared to the malt or feed cultivars. Variations in nutrient concentrations were measured among the adjunct and all-malt cultivars, which could potentially affect the malting and brewing qualities. Grain yield, quality, nutrient concentrations and nutrient removal varied among cultivars grown under identical environmental conditions, which may influence end-use.     

Yield response of spring wheat cultivars (Triticum aestivum and T. turgidum) to inoculation with Azospirillum brasilense under field conditions

Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar Miriam showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar Miriam to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.     

Elevated carbon dioxide and nitrogen supply affect photosynthesis and nitrogen partitioning of two wheat varieties

The response of wheat to elevated carbon dioxide concentration (e[CO₂]) is likely to be dependent on nitrogen supply. To investigate the underlying mechanism of growth response to e[CO₂], two wheat cultivars were grown under different carbon dioxide concentration [CO₂] in a chamber experimental facility. The changes in leaf photosynthesis, C and N concentration, and biomass were investigated under different [CO₂] and N supply. The result showed an increase in photosynthesis under e[CO₂] at all N level except the one with the lowest N supply. Furthermore, a significant decrease in g_s and Tr for both the cultivars was also observed under e[CO₂] at all N levels. A considerable increase in WUEi was observed for both the cultivars under e[CO₂] at all N levels except for the lowest concentration one. Therefore, the study shows that a stimulation of plant growth under e[CO₂] to be marginal at higher N supply.     

Choice of nitrogen fertilizer affects grain yield and agronomic nitrogen use efficiency of wheat cultivars

Abstract

Nitrogen use efficiency (NUE) is low in cereals especially in wheat. Different wheat cultivars may vary in NUE due to inherited biological nitrification inhibition (BNI) potential. In this study, three wheat cultivars (Punjab-2011, ARRI-2011 and Millat-2011) were fertilized at the rate of 140?kg ha^?1 with three N sources [nitrophos (NP), urea and calcium ammonium nitrate (CAN)]. The soil nitrate (NO₃^?)-N contents were significantly enhanced coupled with simultaneous decrease in ammonium (NH₄⁺)-N contents in the rhizosphere of cultivar Punjab-2011, fertilized with NP; however, cultivar Millat-2011 receiving urea behaved in contrast. Wheat cultivar Punjab-2011 fertilized with NP had the highest grain yield and agronomic NUE than other treatments due to significant increase in chlorophyl contents, allometric and yield parameters. The highest net benefit was recorded from the cultivar Punjab-2011 fertilized with CAN. In conclusion, use of NP in Punjab-2011 enhanced the grain yield and agronomic NUE.