Nitrogen and water effects on wheat yield in a Mediterranean-type climate: I. Growth,water-use and nitrogen accumulation

Available soil water is the principal factor that limits the yield potential of wheat (Triticum aestivum L.) and its response to nitrogen (N) under Mediterranean climatic conditions. We examined wheat yield, N fertilizer uptake, and water use for two seasons (1991/1992 and 1992/1993) with total seasonal rainfall of 323 and 275 mm, respectively. In addition to natural rainfall, supplemental irrigation at various rates (1/3, 2/3 and full irrigation) was also considered in assessing these parameters and their interactive effects. Grain yield and dry matter accumulation and N uptake varied between years, mainly due to rainfall and sowing date. Yields were increased by irrigation and N fertilization, with a greater response to N in 1991/1992 and to irrigation in the relatively drier 1992/1993 season. Most fertilizer N was taken up from tillering to anthesis; then it either stabilized or slightly declined, while soil N contributed further to plant N uptake. Compared to rain-fed conditions, more soil and fertilizer N was utilized by the irrigated crop, particularly in 1992/1993. In both years, grain N represented 60% of N accumulated at anthesis under rain-fed conditions, compared to 80% under irrigation. Fertilization and irrigation increased water-use efficiency, particularly under drier conditions. Thus, supplemental irrigation, applied at a sensitive growth stage, would be a valuable management practice for improving yield, water-use efficiency and crop N uptake under the dry conditions of a Mediterranean climate. Given the potential of both irrigation and N to increase output in dry areas, the amounts of both inputs are dictated by rainfall in any one year.     

Growth, yield and water productivity of zero till wheat as affected by rice straw mulch and irrigation schedule

Intensive cultivation of rice and wheat in north-west India has resulted in air pollution from rice straw burning, soil degradation and declining groundwater resources. The retention of rice residues as a surface mulch could be beneficial for moisture conservation and yield, and for hence water productivity, in addition to reducing air pollution and loss of soil organic matter. Two field experiments were conducted in Punjab, India, to study the effects of rice straw mulch and irrigation scheduling on wheat growth, yield, water use and water productivity during 2006-2008. Mulching increased soil water content and this led to significant improvement in crop growth and yield determining attributes where water was limiting, but this only resulted in significant grain yield increase in two instances. There was no effect of irrigation treatment in the first year because of well-distributed rains. In the second year, yield decreased with decrease and delay in the number of irrigations between crown root initiation and grain filling. With soil matric potential (SMP)-based irrigation scheduling, the irrigation amount was reduced by 75 mm each year with mulch in comparison with no mulch, while maintaining grain yield. Total crop water use (ET) was not significantly affected by mulch in either year, but was significantly affected by irrigation treatment in the second year. Mulch had a positive or neutral effect on grain water productivity with respect to ET (WP_ET) and irrigation (WP_I). Maximum WP_I occurred in the treatment which received the least irrigation, but this was also the lowest yielding treatment. The current irrigation scheduling guidelines based on cumulative pan evaporation (CPE) resulted in sub-optimal irrigation (loss of yield) in one of the two years, and higher irrigation input and lower WP_I of the mulched treatment in comparison with SMP-based irrigation scheduling. The results from this and other studies suggest that farmers in Punjab greatly over-irrigate wheat. Further field and modelling studies are needed to extrapolate the findings to a wider range of seasonal and site conditions, and to develop simple tools and guidelines to assist farmers to better schedule irrigation to wheat.     

Effects of irrigation and nitrogen on growth, light interception and efficiency of light conversion in wheat

Effects of three irrigation treatments (rainfed, and irrigation at 7-day and 14-day frequencies beginning in spring) and two rates of nitrogen (0 and 150 kg N ha⁻¹) on growth, light absorption, and conversion efficiency in wheat were studied. Growth was considered in four phases extending from 95 days after sowing ( 95) to the beginning of rapid stem growth ( 120), the stem growth-phase lasting to the onset of rapid grain-filling ( 148), the grain-filling phase between 148 and 170, and the final period to harvest. The first irrigation treatments were applied at 120.Radiation interception was the major determinant of growth. Rainfed treatments captured ca. 1100 MJ m⁻² between 95 and 148, by which time they had achieved maximum above-ground biomass. Irrigated treatments continued to grow until 170. They captured ca. 1300 MJ m⁻² to 170 where no nitrogen was applied, and ca. 1500 MJ m⁻² where N was applied.In addition to effects on leaf-area duration and radiation absorption, treatments also affected conversion efficiency, ε. In the first phase, ε increased from 0.85 g MJ⁻¹ to 1.15 g MJ⁻¹ where N was applied. After 120, irrigation increased ε from a mean of 0.8 g MJ⁻¹ in rainfed treatments to 1.2 g MJ⁻¹. In the periods of rapid stem-growth and grain-filling, ε was a maximum of 1.45 g MJ⁻¹ in the frequently irrigated treatment which received N, resulting in a maximum above-ground biomass of 2100 g m⁻². Mean maximum biomass was 1670 g m⁻² in the other irrigated treatments, as compared with a mean of 1100 g m⁻² in rainfed treatments.Growth rates were compared with predicted potential rates. After accounting for differences in light absorption between treatments, rates of growth ranged between 0.4 and 0.65 of potential rates in treatments other than I_wN₁₅₀, in which the growth rate between 120 and 170 was almost 0.8 of the potential rate. These proportions were strongly correlated with estimates of ε, although the relationship varied between phases as a result of differences in global radiation. Collectively, the data suggest that physiological constraints, associated with both N and water, contributed to differences in rates of growth in addition to those imposed by leaf-area duration and radiation absorption.The yield potential of the frequently irrigated treatment which received N was, however, not realised in the field. Lodging after 162 was estimated to decrease yield from a potential of ca. 900 g m⁻² to 650 g m⁻².     

Root growth,soil water variation,and grain yield response of winter wheat to supplemental irrigation

Water shortage threatens agricultural sustainability in the Huang-Huai-Hai Plain of China. Thus, we investigated the effect of supplemental irrigation (SI) on the root growth, soil water variation, and grain yield of winter wheat in this region by measuring the moisture content in different soil layers. Prior to SI, the soil water content (SWC) at given soil depths was monitored to calculate amount of irritation water that can rehydrate the soil to target SWC. The SWC before SI was monitored to depths of 20, 40, and 60 cm in treatments of W20, W40, and W60, respectively. Rainfed treatment with no irrigation as the control (W0). The mean root weight density (RWD), triphenyl tetrazolium chloride reduction activity (TTC reduction activity), soluble protein (SP) concentrations as well as catalase (CAT), and superoxide dismutase (SOD) activities in W40 and W60 treatments were significantly higher than those in W20. The RWD in 60–100 cm soil layers and the root activity, SP concentrations, CAT and SOD activities in 40–60 cm soil layers in W40 treatment were significantly higher than those in W20 and W60. W40 treatment is characterized by higher SWC in the upper soil layers but lower SWC in the 60–100-cm soil layers during grain filling. The soil water consumption (SWU) in the 60–100 cm soil layers from anthesis after SI to maturity was the highest in W40. The grain yield, water use efficiency (WUE), and irrigation water productivity were the highest in W40, with corresponding mean values of 9169 kg ha^?1, 20.8 kg ha^?1 mm^?1, and 35.5 kg ha^?1 mm^?1. The RWD, root activities, SP concentrations, CAT and SOD activities, and SWU were strongly positively correlated with grain yield and WUE. Therefore, the optimum soil layer for SI of winter wheat after jointing is 0–40 cm.     

Effects of antitranspirants on yield,grade distribution,and water use of potatoes

The influence of two antitranspirant materials on yield and grade distribution of potatoes was studied during 1975 and 1976. An experimental material (AmChem 74-A335)³ was tested in 1975 at 1:9 concentration in water and 150 gal. of spray per acre (1402 1/ha). Yields of >8 oz. Norgold Russet tubers were increased by 96 cwts per acre (10741 Kg/ha) with no change in total yield. The yield increase was due to an increase in tuber size, as total numbers remained unchanged. Formulation problems rendered the material unavailable for tests in 1977. In 1976 a different antitranspirant (Folicote)³ was studied at Lubbock and Hereford at 1:100 and 1:50 concentrations in 50 gal. water (1402 1/ha). Applications were made at bloom and four weeks later. The Lubbock trial included two irrigation regimes and in each trial both Red LaSoda and Norgold Russet response was studied. The antitranspirant resulted in yield increased of >8 oz. grade Norgold Russet potatoes at Lubbock with no effect on total yield. Total yield of Red LaSoda potatoes was increased by 135 cwts in plots irrigated less frequently at Lubbock with no increase in more frequently irrigated plots at Lubbock and Hereford. Antitranspirants reduced peak soil moisture tension levels by 10–15 centibars (cb) for several weeks after application indicating the potential for extending the period between irrigations.     

密度和氮肥用量对油菜产量及氮肥利用率的影响?

 为机械化种植油菜,研究不同施氮水平下密度对直播油菜生长发育和氮肥利用效率的影响。以甘蓝型油菜品种中双11号为材料,在低密（15万株/hm2）和高密（45万株/hm2）两种密度下,设施氮0、90、180和270kg/hm2处理,分析施氮量与密度对油菜农学性状、产量、氮肥利用效率的影响,并对比分析了密度与油菜需氮量之间的关系。结果表明,增密后油菜的株高、分枝数、单株角果数和每角粒数显著降低,分枝高度和千粒重显著增加。高密油菜群体株型结构整齐均一,更能满足机械化收获需要。高密处理油菜籽粒产量高于低密处理。施氮0～180kg/hm2时,两个密度下的籽粒产量均随施氮量增加而显著提高,但在270kg/hm2时两密度下油菜产量均有所下降。油菜氮肥表观利用率随着施氮量的增加而下降,但是又随种植密度的增加而增加。说明增加密度能促进氮素向油菜籽粒转移,降低每生产100kg籽粒油菜需氮量,提高氮肥表观利用率。在相同的目标产量（低密下的经济产量、湖北省油菜平均单产和全国油菜平均单产）下,油菜增密后可以节约氮肥用量22.9%~30.6%,增密减氮效果明显。       

Effects of variety and fertiliser nitrogen on alcohol yield, grain yield, starch and protein content, and protein composition of winter wheat

The effects of nitrogen (N) fertiliser on grain size and shape, starch and protein concentration, vitreosity, storage protein composition, and alcohol yield of two winter wheat varieties contrasting in endosperm texture were studied in a field trial in Herefordshire, UK in 2004. Averaged across varieties, the alcohol yield was 439 L/tonne for grain with a protein concentration of 11.5 g/100 g. The soft endosperm wheat variety Riband produced on average 7.7 L more alcohol per tonne of grain at a given protein concentration than the hard endosperm variety, Option. At the same time, N fertiliser was shown to have significant effects on alcohol production through its major influence on grain protein concentration. Averaged over both varieties, there was a reduction in alcohol yield of 5.7 L for each 10 kg increase in protein content per tonne of grain. The starch concentration of Riband was 2.9 g/100 g higher than Option at a given grain protein concentration, supporting its higher observed alcohol yields. A low conversion of starch to alcohol in this study (6.30 L/10 kg starch) compared to the theoretical value (6.61 L/10 kg starch) indicated that there is potential for improvement of this character. The traits relating to grain size and shape were principally influenced by genotype, and were not influenced by N fertiliser. Conversely, there were only minor genotypic effects on grain protein concentration and vitreosity. An important finding was that there were no interactions between variety and N treatment for any of the variables considered, indicating that the response of the two varieties to changes in applied N was the same, resulting in consistent differences in starch concentration and alcohol yield between genotypes at different levels of grain protein. An analysis of the composition of the wheat storage proteins by size-exclusion chromatography showed that the gliadins increased on average by 0.56 g per g increase in total grain protein and were quantitatively the major protein fraction, suggesting that selection for low gliadin content may be a desirable means by which to reduce grain protein, and thereby increase alcohol yield in wheat. The relationship between alcohol yield per unit area and applied N rate was described by a quadratic function and the maximum alcohol yield per unit area was ca. 3630 L/ha. Statistical analysis suggested that the economic optimum rate of N applied for grain yield was close to the optimum N rate for maximum alcohol productivity.     

The effect of timing and severity of water deficit on growth,development, yield accumulation and nitrogen fixation of mungbean

Mungbean (Vigna radiata L.), as a dryland grain legume, is exposed to varying timing and severity of water deficit, which results in variability in grain yield, nitrogen accumulation and grain quality. In this field study, mungbean crops were exposed to varying timing and severity of water deficit in order to examine: (1) contribution of the second flush of pods to final grain yield with variable timing of relief from water deficit, (2) the sensitivity to water deficit of the accumulation of biomass and nitrogen (N) and its partitioning to grain, and (3) how the timing of water deficit affects the pattern of harvest index (HI) increase through pod filling. The results showed that the contribution of the second flush to final yield is highly variable (1–56%) and can be considerable, especially where mid-season stress is relieved at early pod filling. The capacity to produce a second flush of pods did not compensate fully for yield reduction due to water stress. Relief from mid-season stress also resulted in continued leaf production, N₂ fixation and vegetative biomass accumulation during pod filling. Despite the wide variation in the degree of change in vegetative biomass and N during pod filling, there were strong relationships between grain yield and net-above-ground biomass at maturity, and grain N and above-ground N at maturity. Only in the extreme situations were HI and nitrogen HI affected noticeably. In those treatments where there was a large second flush of pods, there was a pronounced biphasic pattern to pod number production, with HI also progressing through two distinct phases of increase separated by a plateau. The proportion of grain yield contributed to by biomass produced before pod filling varied from 0 to 61% with the contribution greatest under terminal water deficit. There was a larger effect of water deficit on N accumulation, and hence N₂ fixation, than on biomass accumulation. The study confirmed the applicability of a number of long-standing physiological concepts to the analysis of the effect of water deficit on mungbean, but also highlighted the difficulty of accounting for timing effects of water deficit where second flushes of pods alter canopy development, biomass and yield accumulation, and N dynamics.     

Influence of irrigation and nitrogen management on potato yield and quality

The effects of irrigation, water and nitrogen management on yield and quality of the Russet Burbank cultivar are discussed relevant to developmental stages of growth. Recent research on the interactions of irrigation and nitrogen management on total and U.S. No. 1 yields and specific gravity are presented. Total and U.S. No. 1 yields decline with increasing soil moisture stress. Yield of U.S. No. 1 potatoes is particularly sensitive to short periods of irrigation deficit during tuber initiation. Total yield appears most sensitive to short periods of irrigation deficit during tuber bulking. Allocation of longer term irrigation deficits during years of limited water supply should be either a) avoided during mid-season tuber bulking, or b) uniformly distributed over the entire tuber bulking growth period. Yield increases with higher total available soil nitrogen under deficit irrigation, but the yield response diminishes as the amount of total seasonal water decreases. The influence of irrigation and nitrogen availability is also discussed for specific gravity and tuber maturity. Seasonal (split) nitrogen management is proposed as a method to improve yield, quality and nitrogen fertilizer use efficiency of indeterminant cultivars.     

灌水对大豆产量及化学品质的影响

采用田间小区试验,研究灌水对高油大豆和高蛋白大豆品种产量和品质的影响.试验结果表明,灌水使高油大豆的产量略有提高,较对照增产1.9%,对高蛋白大豆产量未表现出增产效果.灌水对不同品质的大豆蛋白质和脂肪含量影响不同,灌水可提高高油大豆品种脂肪含量,降低蛋白质含量.相反,灌水提高高蛋白大豆品种蛋白质含量,降低脂肪含量.     

施氮量对蓖麻花后干物质积累、产量和产量构成的影响

本试验研究了不同施氮量（0、150、 270和390 kg.hm-2）对淄蓖3号蓖麻群体干物质积累与分配、产量和产量构成的影响。结果表明,开花前蓖麻全株和各器官干物质积累速率均缓慢,开花后积累速率快速增加。施氮对各器官和整株干物质的积累有明显影响。施氮量为150 kg.hm-2的处理在开花期和灌浆期花序的干物重积累速率最高,比较有利于茎和叶片中储存的营养物质向花序等产量器官转运,促进果穗形成和籽粒灌浆,从而促进产量的提高。施氮量为270和390 kg.hm-2的处理在开花期和灌浆期茎和叶干物重积累速率过高,而花序的积累速率较低,不太利于茎和叶片中储存的营养物质向花序等产量器官运转,影响了产量的进一步提高。在本试验条件下,施氮量为150 kg.hm-2和270 kg.hm-2时,每株粒数显著增加,但施氮量增加到390 kg.hm-2时,与270 kg.hm-2处理相比,每株粒数有所下降。对于百粒重,施氮量为150 kg.hm-2处理的增重效果最好,270 kg.hm-2和390kg.hm-2处理虽然也能增加百粒重,但增加效果逐渐降低。从整体产量表现看,以施氮量为150 kg.hm-2处理的产量最高,达到6291.69 kg.hm-2,其次为270 kg.hm-2和390 kg.hm-2处理,分别达到6243.03kg.hm-2和5179.05kg.hm-2。     

Effect of irrigation and nitrogen fertilization on biomass yield and efficiency of energy use in crop production of Miscanthus

The perennial C₄ grass Miscanthus has been proposed as a biomass energy crop in Europe. Effects of crop age, irrigation and nitrogen fertilization on biomass and energy yields and N content of Miscanthus were investigated and the energy costs of production determined. After an establishment period of 1 year, cultivation of Miscanthus resulted in a dry matter production of over 37 t ha⁻¹ year⁻¹ over a period of 4 years. Irrigation and nitrogen level greatly affected Miscanthus biomass yield. In absence of N fertilization, irrigation did not modify biomass yield and the effect of irrigation increased with the increase in N level. The average N response ranged from 37 to 50 kg biomass kg⁻¹ N applied. Because the calorific value of Miscanthus biomass (16.5 MJ kg⁻¹) was not affected by irrigation and N fertilization, energy production depended exclusively on biomass yield. Maximum energy yield was 564 GJ ha⁻¹ year⁻¹. Without N supply and irrigation, energy yield was 291 GJ h⁻¹. Net energy yield, calculated as the difference between energy output and input, but without inclusion of drying costs, was 543 GJ ha⁻¹ with N fertilization and irrigation and 284 GJ ha⁻¹ without; the ratios of energy output to input in crop production were 22 and 47, respectively.     

Decreased nitrogen rates and irrigation effect on celery yield and internal quality

The effect of decreased nitrogen rates (90, 60 and 30 kg N/ha) with and without irrigation on celery yield quantity and internal quality were studied in field experiments in 1993 and 1994. The decreased nitrogen rates reduced yields in both years. In the dry and warm conditions of 1994 nitrogen × irrigation interaction was clearly observed; irrigation increased yield more at higher nitrogen rates than at lower nitrogen rates. In the rainy conditions of 1993 irrigation did not effect the yield level.On the other hand, in both years, decreased nitrogen rates increased dry matter, vitamin C and dietary fiber contents, and nitrogen had a minor effect on total sugar content. In 1994 alpha- and beta carotene and thiamin were also analyzed but nitrogen had no effect on them. Irrigation increased dry matter and total sugar contents at the two lowest nitrogen rates in 1994, but decreased vitamin C contents in both years. There was also slight evidence that irrigation might decrease alpha- and beta-carotene and thiamin contents.     

The effect of irrigation and nitrogen on powdery scab and yield of potatoes

Summary Powdery scab, caused by the fungusSpongospora subterranea, has developed in the Cappodocia region of Turkey because of changes in agronomic practices, such as excessive irrigation and nitrogen fertilizer use and growth of highly susceptible cultivars. The most suitable irrigation and nitrogen application levels were established to maintain powdery scab at minimum levels without affecting potato yield. Three irrigation levels were used in 1998 (673, 897, 1121 mm) and five in 1999 (329, 494, 658, 823, 987 mm). Nitrogen levels were applied 150, 300, 450, 600 kg N ha⁻¹. In 1998, least powdery scab occurred with 673 mm irrigation, which yielded 41 t ha⁻¹ potatoes. The lowest disease severity occurred in 1999 with 494 mm irrigation and 150 kg N ha⁻¹. At these levels, tuber yield was 34 t ha⁻¹ which was not significantly different from the highest yield measured. In 1999 and at two of the three irrigation levels inl998, nitrogen increased disease severity.     

Effect of seedpiece spacing and nitrogen fertilization on tuber yield, yield components, and nitrogen use efficiency parameters of two potato cultivars

The effect of seedpiece spacing on the efficiency of nitrogen (N) use by the potato crop is generally unknown. The objective of this experiment was to determine the effect of seedpiece spacing on tuber yield, yield components and N use efficiency parameters of two potato cultivars. Potato cultivars Atlantic and Shepody were grown at two rates of N fertilization (0 or 100 kg N ha^?1) and three seedpiece spacings (20, 30, or 40 cm) in 2000 to 2002. Wider seedpiece spacing increased mean tuber weight and the number of tubers per stem, but decreased total tuber yield. The higher tuber yield at the narrow seedpiece spacing was attributed to higher biomass production in combination with lower tuber specific gravity. Seedpiece spacing had no consistent effect on plant N accumulation, and therefore no consistent effect on N uptake efficiency (plant N accumulation /N supply from the soil plus fertilizer). However, a small increase in soil NO₃-N concentration in the hill at topkill at wider seedpiece spacing suggested plant N accumulation was slightly reduced at wider seedpiece spacing, but at a level that could not be detected from a plant-based measure of N accumulation. The reduced dry matter accumulation, but similar plant N accumulation, resulted in lower N use efficiency (plant dry matter accumulation / N supply) at wider seedpiece spacing. Wider seedpiece spacing also resulted in generally lower values of N utilization efficiency (plant dry matter accumulation / plant N accumulation) for the 40-cm compared with the 20- and 30-cm seedpiece spacings. Effects of seedpiece spacing on N use efficiency parameters were generally consistent across cultivars and fertilizer N rates. Wider seedpiece spacing did reduce the efficiency of N use by the potato crop; however, the magnitude of the effect was small under the conditions of this study.     

Influence of competition,irrigation levels and nitrogen fertilization on protein content and protein yield of three spring wheat (Triticum aestivum L.) cultivars

Protein content and protein yield of three spring wheat cultivars differing in morphological and physiological growth characters were found to be influenced by intercultivar competition, irrigation levels and nitrogen fertilization. The protein content of the tall cultivar C 306 and the protein yield of the dwarf cultivar HD 2160 were more than the other cultivars. Binary mixed stands were not superior to the better component cultivar. Intercultivar competition increased the protein content of dwarf and semi-dwarf cultivars, but decreased the protein content of tall cultivar. On the other hand, protein yield of the dwarf cultivar decreased and that of tall cultivar increased when grown in mixed stands. Protein yield of semi-dwarf cultivar increased when grown with dwarf cultivar, but decreased when grown with tall cultivar. Two or three irrigations increased the protein content and protein yield of all the three cultivars and their mixed stands over one irrigation. Protein content and protein yield of the cultivars and their mixed stands were higher when 150 kg N/ha was applied than when 80 kg N/ha was applied.     

锰对大豆氮代谢相关指标及产量品质的影响

以大豆品种垦农4号为材料,在大田小区试验的条件下,研究EDTA-Mn浸种和在初花期（R1期）叶面喷施对大豆叶片可溶性蛋白、硝态氮、游离氨基酸含量、硝酸还原酶活性及产量品质的影响。结果表明,无论在浸种处理（A）还是叶面喷施处理（B）中,中浓度锰(即A3 1.54g/L和B3 20g/L)处理对大豆叶片可溶性蛋白、硝态氮、游离氨基酸含量及硝酸还原酶活性均有一定的促进作用,但随着生育期的推进,浸种处理对各指标影响效果逐渐减弱。同时,中浓度的锰处理有利于大豆单株粒数、荚数和单株产量的提高,从而达到大豆增产的目的,且能够使大豆的蛋脂总量明显提高。高浓度的锰(即A4 15.4g/L或B4 60g/L)处理则对上述指标起抑制作用。     

Safflower yield,chlorophyll content,photosynthesis, and water use efficiency response to nitrogen fertilization under rainfed conditions

Safflower (Carthamus tinctorius L.) is a deep-rooted crop which can tolerate water stress and can be grown in rotation with other crop species. Nitrogen is very important for the growth and yield of safflower, however, the effect of N level on chlorophyll content, assimilation rate, transpiration rate, stomatal conductance, substomatal CO₂ concentration, and water use efficiency (WUE) have not been determined. A 2-year field study was conducted with the objective to determine the effect of N fertilization on yield, yield components, chlorophyll content, photosynthetic characteristics, and WUE of safflower grown under rainfed conditions. Three rates of N were used (0, 100, and 200 kg N ha⁻¹) and two hybrids (CW9048 and CW9050). N fertilization increased seed yield by an average of 19%, the seed weight per plant by 60%, the seed weight per head by 18%, the number of heads per plant by 32%, and the number of seeds per plant by 41% compared with the control. N level also affected chlorophyll content, N concentration at anthesis, protein, and oil yield. N application increased assimilation rate by an average of 51%, stomatal conductance of water vapour by an average of 27%, and WUE by an average of 60% over the 2 years of the study when compared to the control. The present study indicates that N fertilization can affect yield, yield components, photosynthetic efficiency, and physiology of safflower under rainfed conditions.     

Sulfur fertilization improves nitrogen use efficiency in wheat by increasing nitrogen uptake

Nitrogen (N) fertilization plays a central role for improving yield in wheat and high N use efficiency (NUE) is desired to protect ground and surface waters. Several studies showed that sulfur (S) fertilization may increase NUE, but no attempts have been made to explain whether this increase is due to greater recovery efficiency (RE), an enhanced internal efficiency (IE) or by an improvement of both efficiencies. The aim of this study was to analyze the effects of different N and S fertilizer rates, and their interaction on N uptake, its partition at maturity, NUE and its main components. Field experiments were carried out during two consecutive growing seasons in the Argentinean Pampas using a single bread-wheat genotype grown under different combinations of N and S fertilizer rates. Additional experiments were performed in farmer fields using N and S fertilization evaluating different genotypes in order to analyze the components of NUE in other environmental conditions. Plant N uptake increased linearly in response to N addition until rates of ca. 80 kg N ha⁻¹. Sulfur addition showed no effect at the lowest N fertilizer rate, but N uptake was increased when S was applied at the highest N rate, revealing a synergism between both nutrients. At the lowest S rate RE was 42%, and increased to 70% when S fertilizer was added. No changes in IE in response to S fertilization were observed. These results were also observed in farmer field experiments, in genotypes that showed different IE. This study showed that S addition increased NUE mainly by increasing the N recovery from the soil. Thus, the concurrent management of N and S is important for reducing the potential pollution of residual soil nitrate by increasing N recovery from the soil while sustaining high nitrogen use efficiency.