Physical characteristics of corn kernels as influenced by nitrogen fertilization

Abstract

Physical characteristics of corn (Zea mays L.) kernels influence end‐use. Agronomic practices including nitrogen (N) fertilization may influence kernel hardness. The objective of this study was to determine if com endosperm characteristics influence the effect of N fertilization on kernel hardness and breakage susceptibility. In 1988, six corn hybrids differing for endosperm were grown at two locations in Ohio and with two N rates (34 and 200 kg/ha). Kernels of the waxy hybrid were denser less susceptible to breakage than its near‐isogeneic normal counterpart. Soft kernels weighted less and were less dense than hard kernels, but these two hybrid classifications did not differ for breakage susceptibility. Hard kernels possessed a greater resistance to grinding than soft kernels. Increasing N fertilizer rate increased resistance to grinding and reduced susceptibility to breakage of both soft and hard endosperm types. Fertilization with N not only affects corn grain yield, but also affects physical characteristics that are important to end‐users.     

Grain yield and mineral composition of corn as influenced by endosperm type and nitrogen

Abstract

Corn (Zea mays L.) is a major source of nutrition for humans and animals. Chemical and physical properties of corn endosperm vary among hybrids, are influenced by genotype and environment, and may affect the crop's response to nitrogen (N) fertilization. The objective of the study was to measure the responses of grain yield and grain N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe), boron (B), zinc (Zn,) and copper (Cu) concentration of different endosperm types to N fertilization. The study was conducted at two Ohio locations in 1988, where six endosperm types and two N rates (34 and 200 kg N/ha) were combined in a split plot arrangement. Nitrogen rate (main plots) had little effect on yield at either location, and the soft endosperm hybrid was the only hybrid to respond to N fertilizer. Within fertilizer level, hybrids differed in grain yield with the waxy hybrid out yielding the normal endosperm hybrid, and the hard endosperm hybrid out yielding the soft one at the 200 kg N/ha rate. Application of N fertilizer increased the grain N concentration of all hybrids. Grain of the waxy hybrid contained an equal or greater N concentration than the normal hybrid. In contrast, no difference in N level was found between hard and soft endosperm hybrids at either fertilizer level. Climatic conditions and soil fertility differences might have been partly responsible for location effects. Genetic make‐up could have been a factor in differing hybrid response since grain concentration of nutrients Varied by location, endosperm type, and N treatment.     

Laboratory Measurement of Yield and Composition of Dry‐Milled Corn Fractions Using a Shortened,Single‐Stage Tempering Procedure

The objective was to describe a laboratory‐scale dry‐milling procedure that used single‐stage tempering and determine the effect of hybrid on yields and fraction compositions in milled corn. Samples of 11 commercially available hybrids were processed through a laboratory dry‐milling procedure that used 1 kg samples of corn to produce milling fractions of large grits, small grits, fines, germ, and pericarp. Compositions of milling fractions (protein, neutral detergent fiber, ash, and crude fat) were determined. The procedure used a single‐stage tempering step that increased corn moisture from 15 to 23.5% wb during an 18‐min tempering period. Germ were separated from endosperm particles using a roller mill followed by screening over a sieve with 1.68‐mm openings. Coefficients of variability were small, indicating acceptable repeatability. Overall yield means were 39.2, 25.3, 13.8, 78.2, 14.3, and 6.8 g/100 g (db) for large grits, small grits, fines, total endosperm, germ, and pericarp, respectively. There were effects due to hybrid (P < 0.05) on fraction yields and compositions of milling fractions. Correlations (r) among endosperm fractions (large grits, small grits, and fines) ranged from 0.54 to |–0.92|. Correlations among endosperm fractions and germ and pericarp were <0.68. The developed dry‐milling method estimated milling yields among hybrids with low standard deviations relative to the means and should be a useful tool for research and industry in measuring dry‐milling characteristics.     

Effects of nitrogen,phosphorus, and potassium nutrition on yield,rates of kernel growth and grain filling periods of two corn hybrids

Abstract

Depression of corn grain yields from nutrient stress has been studied extensively, but effects of nutrient stress on rates of corn development and yield determinants are less well understood. Nutritional effects on the number of kernels/unit area, growth rate/kernel, and duration of growth have implications concerning fertilization practices and yield potentials of crops. Two corn hybrids with equivalent silking dates but having different grain filling periods were grown in a field experiment. Fertility treatments consisted of a N series receiving 0, 112, or 336 kg of N/ha and a P‐K series receiving factorial combinations of 0, 22, or 112 kg of P/ha and 0, 56, or 224 kg of K/ha. Dates for grain initiation and maturity were determined for each plot along with tissue analyses of ear leaves, grain yields, and kernel weights. Concentrations of N and K in ear leaves generally corresponded to treatment levels of these nutrients, although Pioneer Hi‐bred 3390 appeared to be less efficient than Pioneer Hi‐bred 3334 in K uptake. Effects of nutrient stress on yield determinants depended on the determinant and nutrient under consideration. Severe N stress did not change length of grain filling periods, but decreased kernel numbers 30 to 70%. Stress for K, on the other hand, shortened grain filling periods about 13% and had only a slight effect on kernel number. Negligible P stress occurred in the experiment. The two hybrids produced equal quantities of grain/ha/day but the hybrid with a longer filling period (Pioneer 3334) filled many more kernels at a slightly slower rate and for a longer period of time to give a significantly greater grain yield compared to Pioneer 3390.     

施氮量对杂交棉氮、磷、钾吸收利用和产量及品质的影响

在高产条件下,研究了不同施氮量对杂交棉氮、磷、钾的吸收利用和产量及品质的影响。结果表明,增施氮肥显著提高了杂交棉氮、磷、钾的积累量,特别是显著提高了杂交棉后期氮、磷、钾的积累量和积累比例。施氮量N300 kg/hm2的子棉产量最高,比施氮量N 225 kg/hm2处理增产0.9%,但差异不显著。氮、磷、钾养分利用效率随施氮量增加而提高;但氮肥利用率随施氮量的增加而下降。施氮可以显著提高纤维长度和纤维比强度,而不同施氮量处理间纤维长度和比强度差别不大。     

施氮量对甜玉米产量、品质和蔗糖代谢酶活性的影响

以甜玉米扬甜2号和超甜135为材料,设置纯氮N 0、75、225、375 kg/hm2 4个处理,研究不同施氮量对甜玉米产量、品质和蔗糖代谢酶活性的影响.结果表明,施氮显著提高甜玉米扬甜2号和超甜135鲜穗产量,两品种均以施N 225 kg/hm2产量最高,比不施氮分别增产65.15％、99.61％.甜玉米籽粒发育过程中可溶性糖和蔗糖的含量随吐丝时间呈单峰曲线变化,施氮明显提高籽粒可溶性糖和蔗糖含量,施氮量为N 225 kg/hm2时最高.氮肥对甜玉米质构特性有较大影响,施氮量增多,籽粒的硬度显著增加;脆性随着施氮量的增加表现出先升高后降低的趋势,其中以氮肥用量在N 225 kg/hm2最大.籽粒中蔗糖磷酸合成酶(SPS)和蔗糖合成酶(SS)合成方向活性的变化趋势与蔗糖含量变化一致,SS分解方向活性随籽粒灌浆进程逐渐变大.合理施氮可提高甜玉米籽粒中SPS和SS合成方向活性,增加糖分,改善品质.     

Nitrogen Fertilizer Increases Seed Protein and Milling Quality of Rice

Rice grain breakage during milling is a problem in many parts of Asia. It has been suggested that nitrogen (N) fertilizer can improve the milling quality of rice. Therefore, this study investigates effects of N fertilization on grain N concentration, endosperm storage protein distribution, and milling quality of rice. Four Thai extra long grain commercial rice cultivars (KDML105, KLG1, PTT1, and CNT1) were grown at Chiang Mai University in the wet season of 2001 with 0 or 120 kg of N/ha at flowering. Anatomical sections showed that there was more storage protein accumulated in the lateral regions of polished grain of high N concentration than in grain of low N concentration. Percent (%) unbroken rice was positively correlated with relative abundance of storage protein in the lateral region of the endosperm in all cultivars. Applying N increased head rice N concentration in all cultivars, whereas % unbroken rice was increased in KLG1 and CNT1. KDML105 cultivar, on the other hand, already had high % unbroken rice and more abundant storage protein in the lateral region with the grain of low N concentration. It is hypothesized that high density of storage protein in the lateral region of the endosperm provides resilience and lessens grain breakage during milling. The additional protein may increase hardness in rice grains and thus could make the rice more resistant to breakage during milling. Furthermore, N fertilization may enhance the nutritional quality of rice grain by increasing the glutelin content, which is rich in lysine.     

Corn yield and shifts among corn quality constituents following application of different nitrogen fertilizer sources at several times during corn development

Corn plants grown under higher nitrogen (N) fertility have a higher grain protein concentration. However, it is not known whether the increased protein concentration is due to decreases in the concentration of non‐structural carbohydrate (energy content approximately equal to protein), lipid (energy content approximately 2.5 times that of protein), or other components (largely structural carbohydrate). An increase in protein concentration that results in a decrease in lipid concentration will decrease the energy content per unit dry weight of grain corn. A 3‐year field experiment was conducted at four locations in Eastern Canada to evaluate the effects of N fertilizer source, application rate, and application time on the yield and quality of corn (Zea mays L.). Ammonium nitrate, urea, and calcium ammonium nitrate were applied at rates of 90 and 180 kg N/ha. The N fertilizer was applied as a) a single application: entirely pre‐plant incorporated (PPI), b) in two applications: 1/2 PPI and 1/2 when corn plants were 15 cm tall, and c) in three applications: 1/3 PPI, 1/3 when plants were 15 cm tall, and 1/3 when plants were 90 cm tall. Corn grain protein concentration increased with N application in all the location‐years; the average increase was 8.40%, with the application of N fertilizers as compared to the control. The protein content (nig) per kernel increased with N application in half the cases. Both corn grain protein concentration and content were not different among the three N application timings in most location‐years. The lipid concentration of the grain was not affected by any N treatment indicating that the increase in protein concentration did not decrease in energy concentration. However, the concentration of remaining grain components (largely fibre and cellulose) decreased as the protein concentration increased, so that high N fertility may have increased both protein and energy concentrations of the grain. Grain yield increased with increasing N fertilizer application rate, and it was generally not significantly affected by the number of the N application times. Neither corn yield nor corn quality were affected by the different N sources.     

Late nitrogen application increased protein concentration but not baking quality of wheat

Late application of nitrogen (N) fertilizers at heading or anthesis is usually performed to produce wheat (Triticum aestivum L.) with high bread‐making quality. However, increasing energy costs and ecological problems due to N losses call for efficient and simplified N fertilization strategies. This study aimed to investigate the effect of late N fertilization on grain protein quality and thus baking quality and to evaluate if similar wheat quality can be maintained without late N application. Field experiments with two winter wheat cultivars differing in quality groups were conducted. The fertilization treatments comprised a rate of 220 kg N ha^?1 applied in two or three doses (referred to as split N application), and 260 kg N ha^?1 applied in four doses (additional late N fertilization) with different N fertilizer types. The results show that although split N application had no effect on grain protein concentration (GPC), it affected N partitioning in the grain, increasing mainly the concentration and proportion of the glutenin fraction. As a result, baking quality was improved by split N application. Late N fertilization enhanced GPC and the relative abundance of certain high molecular weight glutenin subunits (HMW‐GS). However, it had no effect on N partitioning in the grain and did not further improve baking quality. No obvious differences were found between N fertilizer types on grain yield and quality. The N fertilization effect was more pronounced on the wheat cultivar whose baking quality was more dependent on protein concentration. In evaluating baking quality of wheat flour, gliadin and glutenin proportions were better correlated with loaf volume than the overall protein concentration.     

Effets des engrais N,P et K sur le rendement et la qualite de l'ensilage ue mais

Abstract

Thirteen fertility trials were made throughout Quebec's corn growing region during 1972–74. These included eleven fertilizer combinations with corn silage as the test crop and were carried out on nine soils. Total dry matter and digestible nutrients (TDN) varied greatly from year to year, though, mean yields increased by 23 and 30 percent respectively with the 50 kg N/ha treatment, compared to control receiving no nitrogen fertilization. However, 150 kg N/ha was required to attain a maximum yield of 1250 kg/ha crude protein. Despite a 0.2 percent nitrate content found in the silage grown on the most northerly site, a 120 kg P/ha combined with 100 kg N and K gave the highest mean TDN production (9580 kg/ha).

Potassium fertilization affected plant K content of corn grown at the most northerly site only, where a 0.5 percent was found with the control on a suit containing low potassium levels. Further, striking increases in Ca and Mg concentrations were observed with corn grown on that soil. However, magnesium concentration ranging from 0.11 to 0.14 percent were found with nine field trials out of twelve. Also, low K:(Ca + Mg) ratios were found on three trials, which were increased with potassium fertilization levels of 150 kg K/ha. Accordingly, it is suggested that uptakes of 200, 48, 200, 30 and 30 kg/ha of N, P, K, Ca and Mg are required for good corn silage crops.     

优化施肥条件下华北冬小麦/夏玉米轮作体系的土壤氨挥发

采用密闭室间歇通气法研究优化施肥条件下华北冬小麦/夏玉米体系的土壤氨挥发损失。结果表明,肥料氮素氨挥发损失主要发生在施肥后的14 d 内, 冬小麦和夏玉米两个生长季氨挥发损失总量及其损失率均表现出随施氮量的降低而降低,玉米季氨挥发损失高于小麦季。习惯施肥小麦季和玉米季氨挥发总量是氮肥减量后移的2.28和2.03倍,而氮肥减量后移处理的小麦和玉米产量显著高于习惯施肥。氮肥后移可节省氮肥30%,是降低氨挥发损失的理想施肥方式。     

Cultivars of canola respond similarly to applied nitrogen in n-deficient soils of south Western Australia

Six cultivars of canola (Brassica napus L.) were grown with six levels of applied nitrogen (N) fertilizer (urea 46% N) at six locations in south Western Australia (SWA) during 2010 and 2011. The aim of the experiment was to determine if the seed yield (SY) increase (response) of the canola and associated herbicide technologies were different to applied N. Open pollinated (OP) and hybrid cultivars of associated herbicide technologies (Triazine Tolerant, TT; Roundup Ready, RR; Clearfield, CL) were used. Varieties had large SY differences with no N applied. Generally, RR hybrid of 2011 tended to have the highest SY, except for Katanning 2011 where several varieties obtained the same SY. The average amount of N required for 90% of the maximum SY was 113 kg N ha^?1 and economic breakeven N rates were less than or equal to 100 kg applied N ha^?1. The average rate of return on investment in fertilizer N was $1.60.

In four out of six experiments RR hybrids had the highest oil concentration with no applied N. N decreased the oil concentration in all canola types, except at Gibson 2010. At Gibson in 2010, N application increased the oil concentration to about 100 kg N ha^?1 with further additions of N decreasing the oil concentration. There was a linear relationship where N application decreased the oil concentration and increased protein concentration of the seed. In this study, the summation of oil percentage and protein concentration in the seed was on average 65%, with RR hybrids producing 67%.

In most aspects, RR hybrids outperformed RR, OP and other canola types; however, hybrid TT and hybrid CL canola did not consistently outperform their OP counterpart. We suggest that current N fertilizer recommendation models are useful for all canola types currently grown in SWA; however, adjustments should be made to take into account the higher SY and oil concentration potential of RR hybrids compared to TT canola at every rate of applied N.     

长期肥料定位试验栗钙土中磷肥在莜麦上的产量效应及行为研究

研究了高寒半干旱区8年肥料定位试验中,磷肥和有机肥在莜麦上的产量效应、土壤磷素的平衡、土壤Olsen-P及各形态无机磷的变化。结果表明,单施磷肥(N0P1)莜麦增产30.8%、单施氮肥(N1P0)增产109.4%、氮肥和磷肥配合(N1P1)施用莜麦增产314.0%;NP间表现出显著正交互作用,NP(N1和P1)交互作用增产86.9%;施用22.5和45.0.t/hm2有机肥分别比N0P0处理增产115.1%和220.1%;施用有机肥基础上增施磷肥无明显增产效应。不同施肥处理土壤Olsen-P和各形态无机磷的增减取决于土壤磷素的积累与消耗量,7年不施磷肥土壤Olsen-P降低3.3mg/kg。施用磷肥和有机肥土壤各形态磷库均有不同程度的积累;土壤磷素积累以无机磷为主,其中Ca2-P和Ca8-P的积累量分别占土壤无机磷变化总量的19.3%和25.4%,Al-P和Fe-P分别占23.8%和14.8%,O-P和Ca10-P共占13.0%。依据土壤磷素收支平衡状况计算出维持土壤磷素平衡的P2O5用量为45.0.kg/hm2。根据肥料效应函数计算出有机肥用量为0、22.5.t/hm2时,P2O5的最高产量用量分别为98.4.kg/hm2和87.4.kg/hm2。     

Response of tall fescue to fertilizer placement at different levels of phosphorus,potassium, and soil pH 1

Fertilizer application, particularly nitrogen (N), is important in cool‐season grass forage production. Subsurface (knife) placement of N often has resulted in higher forage yield and N uptake of tall fescue (Festuca arundinacea Schreb.) compared to surface‐broadcast fertilization, but further studies were needed to indicate whether soil pH, phosphorus (P), or potassium (K) modifies the response. Experiment I tested responses of forage yield and N and P concentration to N, P, and K amount and placement. Two types of fertilizer placement ‐ broadcast and knife ‐ were used with 13, 112, or 168 kg N; 0 or 19 kg P; and 0 or 37 kg K/ha in a factorial arrangement. Yields increased by 53% as N fertilization went from 13 to 112 kg/ha and by 69% as N increased from 13 to 168 kg N/ha. Forage yield was increased 26% from knife compared to broadcast fertilizer placement. P application increased forage production by 13%, but K application had no effect on yield. Forage N concentrations increased by 25% as N fertilization went from 13 to 112 kg/ha and by 38% as N increased from 13 to 168 kg N/ha. Effects of added P and fertilizer placement on N concentration often resulted in interactions among factors. Forage P generally was increased by added P, with some effects of interactions among N rate, P rate, and placement. In Experiment II, fescue responses to N placement were tested where different soil characteristics had been established by previous lime and fertility treatments. Forage yield, N concentration, and N uptake were highest where 9.36 Mg/ha of lime were applied as compared to the control. Previous fertility treatments had no significant (P<0.05) effect. When N was knifed, forage yield was related positively to available soil P but not to pH or K. Yield and forage N concentration and uptake were increased by 20, 11, and 33%, respectively, as a result of knife versus broadcast N application.     

Navy bean yield and maturity response to nitrogen and zinc 1

Dry bean (Phaseolus vulgaris L.) generally responds to nitrogen (N) fertilizer with increased yields, but N can delay maturity and cause yield and quality losses from early fall frost. Maintaining adequate zinc (Zn) nutrition in bean promotes earlier maturity. This study was conducted to determine if Zn application can overcome maturity delays possible with the N recommended for high bean yields. Three zinc sulfate (ZnSO₄) treatments (0 Zn, 5.6 kg Zn/ha banded adjacent to the row, and 11.2 kg Zn/ha broadcast and incorporated) were applied in combination with five N rates (0, 45, 90, 134, and 179 kg/ha). Whole plants were sampled at the R1 growth stage (onset of flowering) and analyzed for N and Zn content. Maturity was estimated by determining the percentage of mature pods at the R8‐R9 growth stage. Yields were estimated by harvesting 12.2 m of row at maturity. Zinc fertilization generally increased mature‐pod percentages with banded Zn producing the most consistent response. Zinc did not consistently affect bean yield. Yield and mature‐pod percentage generally increased and decreased, respectively, with increasing N rate. Whole‐plant N concentrations increased linearly with increasing N rate but did not differ among Zn treatments. Mean plant Zn concentrations were increased by Zn fertilizer and related well with mature‐pod percentage means. In situations of high available N, short growing seasons, or with late planting, Zn applications can reduce the risk of crop losses from early fall frost.     

Einfluß einer Stickstoff-Spätdüngung auf das Korneiweiß einer lysinreichen Maishybride

Effect of Late Application of Nitrogen on the Grain Protein of a Maize Hybrid Rich in Lysine 1. In pot experiments the influence of an additional late N fertilizer application at time of flowering on a high yielding lysine-rich experimental maize hybrid has been determined. 2. N-fertilization at flowering increased the total-N and the lysine-contant of the grains. The lysine-N in % of total-N was constant at 5,1%. Comparable values from a former investigation with an opaque- and a standard hybrid are 6,0% lysine-N and 4,0% lysine-N of total-N, respectively. 3. The ratio of prolamine to gluteline was 1:1. N-fertilization did not change this ratio. 4. The amino-acid pattern of the single protein fractions, albumine globuline, prolamine and gluteline was very different, but it was not changed by N-fertilization. 5. Dissecting embryo and endosperm, demonstrated that by late N-fertilization the growth of embryo was promoted more than that of the endosperm. The embryo contributed 30% to total-N and 44% to total-lysine-N of the grain and was not changed by the late N-application. 6. At cultivating such improved hybrids it may be expected that the protein quality will not be changed by application of high amounts of N-fertilizer, whereas the protein quantity will be increased.     

Root mass as a determinant of com hybrid response to starter fertilizer

Many studies have shown variable response to starter or row applied fertilizer on corn (Zea mays L.) hybrids. Field experiments with approximately 25 hybrids over three seasons showed that some hybrids responded to row applied fertilizer with large growth and yield increases while others did not respond. The objectives of this study were to compare root and shoot growth of responsive and non‐responsive corn hybrids to starter fertilizer and their uptake of nitrogen (N) and phosphorus (P). Two glasshouse experiments were conducted with hybrids from the field studies found to be most and least responsive to row applied fertilizers. In the first experiment, P was applied at levels of 0,10,20, or 30 mg kg^‐1 and was mixed with either 25 or 100% of the total soil volume (1.5 L). Nitrogen was mixed with the total soil volume in all treatments at a rate of 100 mg pot^‐1. Phosphorus rates in the second experiment were 0, 30, or 60 mg kg^‐1 and the N rate was 200 mg pot^‐1. Fertilizer N and P were mixed with total soil volume or banded 5 cm below the soil surface and 5 cm away from seed. The soil was obtained from the A horizon of Norfolk loamy fine sand (fine loamy, siliceous, thermic, Typic Kandiudult). Time from seeding to harvest was 33 days for the first experiment and 41 days for the second. Root weight of the non‐responsive hybrid was 31 % higher in the first experiment and 48% higher in the second than of the responsive hybrid. Each hybrid responded similarly to starter P (62 to 78% increase in top growth). The responsive hybrid produced a significant (P 0.05) increase in top (92%) and root (76%) weight due to starter N, but the non‐responsive hybrid did not respond to N placement. The lack of response to starter N‐fertilizer was attributed to greater root growth in the non‐responsive hybrid because its top and root weight with broadcast N were about the same as those of the responsive hybrid with banded (starter) N. Since the hybrids differed only in response to starter N, a convenient method to classify corn hybrids with respect to starter fertilizer response is to measure top growth at six weeks after planting with banded versus broadcast N applied at planting.     

Dry matter yield and nitrogen recovery from bromegrass in south‐central Alberta as affected by rate of long‐term nitrogen applications

Abstract

A field experiment was conducted on a Thin Black Chemozemic soil at Crossfield in south‐central Alberta to determine the effect of long‐term application of ammonium nitrate on dry matter yield (DMY), protein yield (PY), protein concentration, N use efficiency and recovery of N applied to bromegrass (Bromus inermis Leyss.) grown for hay. The N fertilizer was applied at 0, 56, 112, 168, 224, 280, and 336 kg N/ha in early spring of every year from 1968 to 1986. The DMY increased with applied N achieving a maximum at 224 kg N/ha, though the rate of increase in DMY from N fertilization was greatest with the first two increments applied (i.e. 56 and 112 kg N/ha). Protein yield and protein concentration maximized at 336 kg N/ha. The DMY was greater with a single‐cut system than with a double‐cut system. The DMY varied from year to year, but it was not closely related to precipitation received during the April to August period (R² = 0.37). However, in some years low DMYs were associated with low precipitation, or a lack of timeliness of rainfall, or a combination of both. The N use efficiency and % N recovery in bromegrass decreased with increasing N rate. The maximum DMY calculated from quadratic regressions ranged from 3.16 t/ha to 7.91 t/ha, and maximum N rate ranged from 205 to 258 kg N/ha. In summary, DMY, PY, and protein concentration increased, and N use efficiency and % N recovery decreased with increasing N rate in this 19‐year study.     

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.     

超级杂交早稻氮肥群体最高生产力及其增长特征

在大田条件下,以普通杂交早稻（荣优9号和五丰优623）为对照,设置5个氮肥水平（分别施N 0、135、165、195和225 kg/hm2）,比较研究了超级杂交早稻（金优458、春光1号、03优66、淦鑫203）氮肥群体最高生产力及其群体特征。结果表明,1）除普通杂交早稻品种和个别超级稻品种（03优66）在165 kg/hm2水平外,其他超级早稻品种均在195 kg/hm2水平下产量达到最高（即表现氮肥群体最高生产力）。超级杂交早稻较普通杂交早稻产量平均增加8.42%,穗数增加10.67%,穗粒数增加13.96%,群体颖花量大是超级杂交早稻生产力提高的主要原因。2）在各品种的最高生产力条件下,与普通杂交早稻相比,超级杂交早稻各生育时期（有效分蘖临界叶龄期除外）的群体叶面积指数均显著提高,且抽穗后群体叶面积指数下降缓慢,群体光合势提高9.00%,从而显著增加了生育中后期的干物质积累量。3）超级杂交早稻氮素吸收总量达182.62（167.53～191.72）kg/hm2,较普通杂交早稻增加20.02%,其中拔节至抽穗期增加30.09%,抽穗至成熟期增加28.92%。与普通杂交早稻相比,超级杂交早稻的氮素农学利用率和生理利用率均明显提高,而氮素吸收利用率和氮素偏生产力却有所降低。