Physiological determinants of maize and sunflower grain yield as affected by nitrogen supply

Utilisation of nitrogen (N) has been closely related to increases in crop productivity. However, not all crops respond similarly and the objective of this study is to identify physiological processes that determine responses to N supply for maize and sunflower. Grain yield in maize (range: 210–1255 g m⁻²) was greater and more responsive to N supply than in sunflower (106–555 g m⁻² in carbohydrate equivalents) over a wide range of total N uptake (3–>20 g N m⁻²). In maize, differences in grain yield among levels of N supply were associated more with variation in biomass than in harvest index. In sunflower, differences in grain yield (in carbohydrate equivalents) among levels of N supply were related similarly to variation in both biomass and harvest index. The decrease in biomass production with decreasing N supply was associated with decreases in both radiation interception and radiation use efficiency (RUE). Decreased interception was due to effects of N supply on reducing canopy leaf area, whereas the reduced RUE was associated with decreased SLN. Total biomass production in maize was more responsive to N supply than in sunflower. The major determinants of the differences in response of biomass accumulation to N supply found between maize and sunflower are: (i) sunflower tends to maintain SLN with increase in partitioning of N to leaves under N limitation whereas maize tends to maintain leaf area with increase in partitioning of biomass to leaves and (ii) the ability of maize to maintain N uptake following cessation of leaf production.     

Radiation interception and use efficiency as affected by breeding in Mediterranean wheat

Past breeding achievements in grain yield were mainly related to increases in harvest index (HI) without major changes in biomass production. As modern cultivars have already high HI, future breeding to improve grain yield will necessarily focus on increased biomass. Improved biomass would depend on our capacity to improve the amount of photosynthetically active radiation intercepted by the crop (IPAR_%) or the efficiency with which the canopy converts that radiation into new biomass (radiation use efficiency, RUE). Four field experiments with a set of wheat cultivars selected, bred and introduced in the Mediterranean area of Spain and that represent important steps in wheat breeding in Spain were conducted in order to identify whether and how wheat breeding in this area affected the amount of IPAR_% and RUE both before and after anthesis. Although there was genotypic variability, cultivars did not show any consistent trend with the year of release of the cultivars for their biomass, pre and post-anthesis IPAR_%, Crop growth rate (CGR) or RUE but, the post-anthesis CGR and RUE of the two oldest genotypes were lower than that of the other cultivars. As the oldest genotypes have lower number of grains per m² than their modern counterparts, it is suggested that post-anthesis RUE in these cultivars was reduced by lack of sinks and therefore further increases in grains per unit area in modern cultivars could permit to improve biomass via increases in post-anthesis RUE.     

Sensitivity of yield and grain nitrogen concentration of wheat, lupin and pea to source reduction during grain filling. A comparative survey under high yielding conditions

Several studies have been conducted to evaluate the response of crops, especially temperate cereals, to different source–sink ratios during grain filling. However, there is much less information about temperate legumes and even less work comparing the two. The objective of this study was to evaluate the response of both grain yield and grain nitrogen concentration of wheat (Triticum aestivum L.), narrow-leafed lupin (Lupinus angustifolius L.) and pea (Pisum sativum L.) to similar source reduction during grain filling. Two field experiments were conducted in a high yielding environment of Southern Chile. In experiment 1 wheat and narrow-leafed lupin were grown for two consecutive years. Experiment 2 evaluated wheat and pea on two sowing dates. In both experiments a reduction in the source–sink ratio was imposed by using black nets that intercepted 90% of the incident solar radiation from the commencement of the linear dry matter accumulation to physiological maturity. Grain yield was differentially (p < 0.01) decreased by the source reduction in lupin (98%), wheat (63%) and pea (26%). Given that these experiments were carried out in a high yielding environment, the higher response of wheat relative to previous studies supports the hypothesis that the higher the yield potential, the higher the source sensitivity of this crops during the grain filling period. On the other hand, source reduction positively affected (p < 0.05) grain nitrogen concentration in wheat (66%) and pea (18%) but negatively affected lupin (40%). The higher sensitivity of grain yield compared to that of grain nitrogen yield was the cause of the positive effect of the lower source–sink ratio recorded in wheat and pea. In contrast, source shortage in lupin decreased grain nitrogen concentration probably as result of the quick response of grain growth to source limitation. The contrasting sensitivities of lupin, wheat and pea to source reduction during grain filling prevent us to see grain yield and quality response of these crops as separate groups, i.e. temperate cereals vs. temperate legumes.     

Effect of tolerance to Septoria tritici blotch on grain yield,yield components and grain quality in Argentinean wheat cultivars

Septoria tritici blotch (STB) caused by Zymoseptoria tritici (Mycosphaerella graminicola) is a major disease of wheat worldwide due to significant losses in grain yield and quality. Disease tolerance is the ability to maintain yield performance in the presence of disease symptoms. Therefore, it could be a useful tool in the management of the disease. Although it is known, that there is disease tolerance to STB in some wheat cultivars, this aspect has not been studied among Argentinean cultivars. The aims of this study were to evaluate genotypic differences in tolerance to STB among Argentinean cultivars, considering the relationship between the area under disease progress curve or the green leaf area or the non-green leaf area duration with the grain yield. In addition the effect of the disease on yield, yield components, test weight, grain protein concentration, wet and dry gluten concentration and the influence of tolerance on these traits was investigated. Field experiments were carried out with ten cultivars in a split-split-plot design during 2010 and 2011. Inoculation treatments were the main plots and cultivars, the subplots. STB significantly reduced grain yield, their components, test weight and increase grain protein and gluten concentration. Cultivar Baguette 10 showed major tolerance to STB, indicated by a consistent low regression slope between the green area duration and yield, while Klein Chaja was non-tolerant due to a high regression slope. However, many cultivars such as Buck Brasil, Buck 75 Aniversario, Klein Escorpion and Klein Flecha had considerably similar regression slopes to Baguette 10, provided good levels of tolerance. Other cultivars presented no significant differences. The correlation coefficient between tolerance and grain yield potential was not significant, suggesting that tolerant high-yielding cultivars can be obtained. No relationship was found between quality group or tolerance with the increase in protein and gluten concentration due to STB either.     

Genotypic variation in linear rate of grain growth and contribution of stem reserves to grain yield in wheat

Grain growth in wheat depends on current photosynthesis and stem water-soluble carbohydrates (WSC). In semiarid regions with terminal drought, grain filling in wheat crops may depend more on stem WSC content than on current assimilates. Reduction in grain yield under drought is attributed to shorter duration of linear grain growth despite increased contribution of stem reserves to grain yield. The amount of stem reserves is measured either by changes in stem dry weight (indirect method) or by stem WSC content (direct method). Genotypic variation in the rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield has not been evaluated in wheat. The objectives of this study were: (i) to quantify the relationship between the direct and indirect measurement of stem reserves during and across the grain-filling period and (ii) to measure the extent of genotypic variation in rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield. Dry weight, WSC content and grain yield of the main stem were measured at 10-day intervals in 11 diverse wheat genotypes under well-watered and droughted-field conditions across 2 years. Drought reduced stem WSC content from 413 to 281 mg and grain yield from 4.6 to 2.5 t ha⁻¹. Stem WSC content and dry weight were positively correlated. Genotypic differences in linear rate of grain growth were significant in well-watered (ranging from 48.9 to 72.4 mg spike⁻¹ day⁻¹) and in droughted-field (ranging from 33.2 to 59.9 mg spike⁻¹ day⁻¹) conditions. Drought, on average, reduced the linear rate and duration of grain growth by 20 and 50%, respectively. Reduction in linear rate ranged from 13 to 43%. The amount of current assimilates and stem reserves contributed to grain yield was reduced, respectively, by 54 and 11% under drought. Genotypic differences in percent contribution of stem reserves to grain yield were significant in well-watered (ranging from 19.1 to 53.6%) and in droughted-field (ranging from 36.6 to 65.4%) conditions. The wheat genotypes responded differently to drought. Main spike grain yield was reduced by 43% under drought due to 26 and 11% reduction in grain weight and number of grains, respectively. Grain yield was correlated with linear grain growth under well-watered (r = 0.96) and droughted (r = 0.83) conditions. The genotypic variation observed indicates that breeding for a higher rate of linear grain growth and greater contribution of stem reserves to grain yield should be possible in wheat to stabilize grain yield in stressful environments.     

Using stress tolerance indicator (STI) to select high grain yield iron-deficiency tolerant wheat genotypes in calcareous soils

Despite large variation among crop genotypes in response to Fe fertilization, there is no reliable indicator for identifying Fe-deficiency tolerant wheat genotypes with high grain yield. The aim of this investigation was to compare the grain yield response of 20 spring and 30 winter bread wheat genotypes to Fe fertilization under field conditions and to select high grain yield Fe-deficiency tolerant genotypes using a stress tolerance indicator (STI). Two individual trials, each one consisting two field plot experiments, were conducted during 2006–2007 and 2007–2008 growing seasons. Spring wheat genotypes (Trial l) and winter wheat genotypes (Trial 2) were planted at two different locations. Two Fe rates (0 and 20 kg Fe ha⁻¹ as Fe-EDTA) were applied. Spring and winter wheat genotypes differed significantly (P < 0.01) in the grain yield both with and without added Fe treatments. Application of Fe fertilizer increased grain yield of spring wheat genotypes by an average of 211 and 551 kg ha⁻¹ in Karaj and Isfahan locations, respectively. By Fe application, the mean grain yield of winter wheat genotypes increased 532 and 798 kg ha⁻¹ in Karaj and Isfahan sites, respectively. Iron efficiency (Fe-EF) significantly differed among wheat genotypes and ranged from 65% to 113% for spring wheat and from 69% to 125% for winter wheat genotypes. No significant correlation was found between Fe-EF and grain yield of spring wheat genotypes under Fe deficient conditions. For winter wheat genotypes grown in Mashhad, Fe-efficiency was not significantly correlated with the grain yield produced without added Fe treatment. The STI was significantly (P < 0.01) varied among spring and winter wheat genotypes. The interaction between location and genotype had no significant effect on the STI. According to these results, the STI should be considered as an effective criterion for screening programs, if a high potential grain yield together with more stable response to Fe fertilization in different environments is desired.     

Grain number and its relationship with dry matter, N and P in the spikes at heading in response to N×P fertilization in barley

The aim of this work was to study the effects of nitrogen (N) and phosphorus (P) deficiencies and their interaction on spike N, P and biomass around flowering in barley (Hordeum vulgare spp. distichum L.) and its relationship with grain number and grain yield. Two experiments were carried out with microcrops grown in 200 l containers using malting barley (cv. Quilmes Palomar). Treatments were a factorial combination of two levels of N and two or three levels of P fertilization. Dry matter partitioning to spikes was not or only slightly affected by nutrient deficiencies. Then, the effects on spike biomass were similar to those on total aboveground dry matter. Although partitioning of N to the spike in N fertilized treatments was lower than in N stressed ones, spike N content was higher in the N fertilized.

Number of grains was positively associated with spike N and P content as well as spike dry matter at heading in both experiments. Number of grains per unit of spike dry matter at heading in N fertilized microcrops tended to be higher than in N stressed ones, though this effect was not associated with N fertilization effects on N concentration in spikes.

Combining these results with others from the literature from wheat crops, we found a strong relationship between number of grains and spike N content at flowering, but this relationship does not seem to be better than that with spike biomass, judged by the regression coefficients. This indicates that the early application of N may induce a higher number of grains than that predicted by increased spike dry weight at flowering, but this additional effect is not universally related to differences in spike N concentration.     

Radiation interception and biomass and nitrogen accumulation in different cereal and grain legume species

The increasing interest in the sustainability of agricultural systems has emphasised the importance of incorporating legumes into cereal production, in spite of their lower and less reliable grain yields. The basis of the poor performance of legumes has been analyzed in a 2-year comparison between varieties of pea, faba bean, durum wheat and triticale, in terms of resource capture and use. The cereals developed a full canopy 350 °Cd earlier than did the grain legumes, and the triticale more rapidly than the durum wheat. This difference, and the 11-day longer duration of the growing cycle of cereals allowed them to intercept more photosynthetically active radiation (PAR) than grain legumes. This, combined with their higher radiation use efficiency (2.35 ± 0.07 vs 2.10 ± 0.05 g MJ⁻¹), resulted in a biomass greater, on average, by about 500 g m⁻². Within the cereals, triticale accumulated 34% more biomass than durum wheat. Radiation interception and nitrogen uptake are closely tied in both cereals and grain legumes. There was no difference between cereals and legumes in the relationship between the amount of nitrogen assimilated and the fraction of intercepted PAR (FIPAR), but there were differences in the form and in the parameters of the relationship between nitrogen assimilated and PAR intercepted. Below a FIPAR of 0.8, the relationship between FIPAR and N uptake is crop independent, underlining the influence of FIPAR on N uptake. The significance of this FIPAR level is that by the time it has been achieved, the plants will have accumulated most of the N present in their biomass at maturity.     

Growth,PAR use efficiency,and yield components of field-grown Vicia faba L. under different temperature and photoperiod regimes

N-fixing legume crops may be a good component of a general plan to improve cropping system efficiency. For this purpose, crop suitability to specific environments must be established. To estimate the yield potential we examined the growth and yield response of faba bean (Vicia faba L.) crops to different thermal and photoperiod regimes. Irrigated field experiments were conducted in northwest Spain for 3 years (2004–2007) with cv. ‘Alameda’ sown on five different dates in each year from mid-autumn to mid-spring. Environmental conditions experienced by plants across sowing dates were largely different. Sowing date had a great influence on biomass, grain yield and its components. This effect was associated with changes in PAR captured, PAR use efficiency (PUE) and biomass allocation to the different organs. Critical leaf area index (LAI_cr) tended to increase and the extinction coefficient, k, to decrease as the sowing date was delayed. Earlier sowing dates intercepted more radiation over the whole season than the spring sowing dates. Greatest crop growth treatments (2nd and 3rd sowing dates) had the highest values of PAR use efficiency probably due to more adequate temperatures for photosynthesis and a large number of reproductive sinks. The highest grain yield (7733 kg ha⁻¹) was obtained with the mid-February sowing date, which produced the most pods and seeds per m², the largest harvest index (62.0%), and large maximum leaf area index (5.41). Low yields of mid-autumn (1st) and mid-spring (5th) sowing dates were associated with reduced pods and seeds per m². Temperature and photoperiod had a large impact on faba bean growth, development, and yield. Best yields were obtained when abundant assimilate supply and moderate temperatures were available during pod set.     

Genetic dissection of grain nitrogen use efficiency and grain yield and their relationship in rice

Breeding for improved grain yield (GY) and grain nitrogen use efficiency (NUE) is an important objective of many rice breeding programs. A better understanding of the genetics of these two complex traits and their genetic relationship is required for more efficient breeding. This study reports the results of a linkage mapping study conducted for these two traits using 127 rice recombinant inbred lines (RILs) derived from the cross of Zhanshan 97/Minghui 63. Phenotypic data were collected under two nitrogen conditions in 2006 and 2007. For NUE, four and six QTLs were identified in 2006 and 2007, respectively. These QTLs were on chromosomes 1, 2, 6, 7 and 11. For GY, nine and five QTLs were detected on chromosomes 1, 2, 7 and 11 in 2006 and 2007, respectively. The phenotypic and genetic correlations between NUE and GY are positive and highly significant. Four genomic regions, including C86-C2340 on chromosome 1, RZ599-R1738 on chromosome 2, RZ471-C1023 on chromosome 7 and R3203-RM20a on chromosome 11, were found to contain QTLs for both NUE and GY. The effects of the co-located QTLs were in the same direction for NUE and GY, providing a genetic basis for the observed positive genetic correlation between the two traits. These genomic regions might be explored for the simultaneous improvement of NUE and GY in breeding.     

Effects of atmospheric CO2 enrichment on biomass,yield and low molecular weight metabolites in wheat grain

Spring wheat (Triticum aestivum L.) was grown in a free-air carbon dioxide (CO₂) enrichment (FACE) field experiment. Grain and biomass yield and its components were determined at maturity and the grain metabolome was analysed by gas chromatography-mass spectrometry (GC–MS). Elevated CO₂ (537 versus 409 μl l⁻¹) increased biomass production except for leaves. In total, levels of 16 grain metabolites were decreased and four were increased. CO₂ enrichment resulted in significant decreases of amino acids such as o-acetyl-L-homoserine, leucine, arginine, L-homoserine and the group of ornithine, arginine and citrulline and negative trends for norleucine, L-aspartate, proline, L-cysteine and tyrosine. The amines D/L-diaminopimelate and alpha-ketoaminobutyrate and the polyamine putrescine were significantly decreased. In contrast, the polyamine spermidine tended to increase under elevated CO₂. Among sugars and sugar derivatives, ribose-5-P was significantly increased, while gluconate-6-P was decreased. There were also negative CO₂-induced effects on sugar alcohols: significant for glycerol-2-P (P = 0.008) and almost significant for myo-inositol-P (P = 0.066). In contrast, organic acids such as pyruvate and glucuronic acid were significantly increased. Overall, the N-rich metabolites especially were reduced. CO₂ enrichment can markedly affect the physiology and metabolome of mature grains which may in turn lead to changes in nutritional status.     

Identification of CIMMYT spring bread wheat germplasm maintaining superior grain yield and quality under heat-stress

Unpredictable temperatures and rainfall associated with climate change are expected to affect wheat (Triticum aestivum L.) production in various countries. The development of climate-resilient spring wheat cultivars able to maintain grain yield and quality is essential to food security and economic returns. We tested 54 CIMMYT spring bread wheat genotypes, developed and/or released over a span of 50 years, in the field for two years under optimum sowing dates, as well as using two delayed sowing dates to expose crops to medium and severe heat-stress conditions. The grain yield and yield components were severely affected as the heat-stress increased. Two contrasting groups of 10 lines each were identified to determine the effect of heat-stress on bread-making quality. The first set included entries that produced high yields in optimal conditions and maintained higher yields under heat-stress (superior-yielding lines), while the second set included genotypes that did not perform well in the environment with high temperature (inferior-yielding lines). We identified genotypes exhibiting bread-making quality stability, as well as the quality traits that had higher correlation with the loaf volume in the environment without stress and under heat-stress. Of all the quality traits tested, dough extensibility (AlvL) and grain protein content had a significant influence in heat-stress adaptation. Most of the lines from the superior-yielding group were also able to maintain and even improve quality characteristics under heat-stress and therefore, could be used as parents in breeding to develop high-yielding and stable quality wheat varieties.     

小麦进化材料氮、磷养分利用效率间的关系

为了揭示小麦进化材料营养特性的变化规律 ,利用 10个不同基因型小麦进化材料 ,研究了其氮、磷养分利用效率 (NU E和 PU E)的变化。发现从二倍体→四倍体→六倍体的进化过程中 ,NUE先逐渐增加 ,到四倍体后变化不大 ;而 PUE则一直下降。造成整株水平上 NU E差异的生理机制在于叶片瞬时光合 NU E的差异 ,瞬时光合NUE主要决定于以干重表示的净光合速率。叶片瞬时 PUE的差异不是造成整株水平上 PUE差异的原因。单叶水平上的 NUE和 PUE联系紧密 ,而整株水平上的 NUE和 PUE存在相对独立性。     

Grain weight,radiation interception and use efficiency as affected by sink-strength in Mediterranean wheats released from 1940 to 2005

Bread wheat has been frequently characterised as sink-limited during grain filling but the degree of sink-limitation could vary with the contribution of breeding in increasing the number of grains per unit land area. This hypothetical change in the level of sink-limitation due to breeding has been insufficiently documented. Two source–sink manipulation experiments under field conditions with three released cultivars and an advanced breeding line representing important steps in wheat breeding in the Mediterranean area of Spain were conducted in order to quantify whether genetic improvement of grain yield in Mediterranean wheat modified the source–sink balance during grain filling, and how it affected grain weight and post-anthesis photosynthetically active radiation intercepted by the crop (IPAR) and radiation use efficiency (RUE). Average grain weight of control and trimmed spikes during grain filling was not significantly affected by halving the number of growing grains in the two oldest cultivars, but it was significantly increased in the most modern line, and had an intermediate response in the intermediate cultivar. In those cases in which a certain degree of source-limitation during grain growth occurred the magnitude of the response reflected a co-rather than a source-limitation. Considering grains from different positions within the spikes the smaller (distal) grains responded more markedly than the larger (proximal) grains. No differences in post-anthesis IPAR were found between the trimmed and control sub-plots for any of the genotypes. However, trimming the spikes reduced post-anthesis RUE, a fact corroborated by a simultaneous reduction in leaf net photosynthetic rate at noon. It seems that bread wheat breeding has tended to reduce the strength of the sink-limitation during post-anthesis even under Mediterranean conditions, and consequently the most modern line presented a sort of co-limitation.     

Late defoliation and wheat yield: Little evidence of post-anthesis source limitation

The effect of source reduction on yield and protein content of bread wheat under well-watered and mild drought stress condition in a semi-arid climate was studied. Field experiments were conducted at the Tehran University research farm during 2003–2004 and 2004–2005 growing seasons. Mild drought stress was imposed when plants were at the second node stage by repeatedly withholding watering and re-irrigating when they showed symptoms of wilting or leaf rolling. Partial defoliations (all leaf lamina other than flag leaves were removed) were imposed at booting and anthesis; complete defoliation was imposed at anthesis (defoliation treatments were applied to all plants of each plot). Drought stress caused a significant increase in the remobilization of pre-anthesis reserves to the grain. Defoliation did not significantly affect remobilization. Grain yield and 1000-grain weight was reduced slightly by drought stress, but in most cases it was not significantly reduced by defoliation. Significant changes were not observed for grain protein content between defoliated and control plots. The results suggested that grain yield of the cultivar used under the condition tested is more controlled by sink than source strength.     

西北绿洲氮磷配施对冬小麦产量及养分利用效率的影响

为了解氮磷配施对西北地区冬小麦产量和养分利用效率的影响.在甘肃凉州区黄羊镇甘肃农业大学试验农场开展了4个施肥处理(N165 P105:165 kg N·hm-2 +105 kg P2O5·hm-2;N165 P165:165 kg N·hm-2 +165kg P2O5·hm-2;N225 P105:225 kg N·hm-2+105 kg P2O5·hm-2;N225 P165:225 kg N·hm-2 +165 kg P2O5·hm-2)的大田试验.结果表明,4个施肥处理中,N165 P105、N225 P165和N165 P165三个处理间产量差异不显著,但均显著高于N225 P105;N165 P105是河西绿洲冬小麦高产节肥的最佳施肥处理.少施N肥有利于WUE的提高(7.89%),而氮磷合理配施才能获得较高的WUE.多施N、P肥可增加N(36.72%)和P(58.94%)的消耗量,但明显降低N(44.48%)、P(53.50%)利用效率,不同处理间N、P利用效率差异显著或极显著,但N、P肥在养分利用上彼此影响不大.因此,肥料的合理配施是提高养分利用效率、实现西北地区高产的主要途径.     

Grain number and grain weight in wheat lines contrasting for stem water soluble carbohydrate concentration

In wheat, the ability to store and remobilise large amounts of stem water soluble carbohydrates (WSC) to grain constitutes a desirable trait to incorporate into germplasm targeted to regions with frequent terminal drought. The main aim of this paper was to examine the relationships between WSC storage, grain number and grain weight across several environments. A small set of recombinant inbred lines (2–4) contrasting in stem WSC were grown in six field trials where water availability, sowing date and/or N level were manipulated, with line yields ranging from 400 to 850 g m⁻² across experiments. Biomass, N and WSC concentration (WSCc, mg g⁻¹ dry weight) and amount (WSCa, g m⁻²) were monitored. A resource-oriented area-based model [Fischer, R.A., 1984. Growth and yield of wheat. In: Smith, W.H., Bante, S.J. (Eds.), Potential Productivity of Field Crops Under Different Environments. International Rice Research Institute, Los Baños, pp. 129–154] and intrinsic rates of organ growth were used to investigate the consequences on grain number of potential competition between spike and stem around flowering.     

Uptake and use efficiency of N, P, K, Ca and Al by Al-sensitive and Al-tolerant cultivars of wheat under a wide range of soil Al concentrations

The impacts of acidic soils and Al toxicity on wheat nutrient economy have been scarcely researched under field conditions even though these soils are widely spread in wheat production areas around the world. The main objective of this study was to quantitatively evaluate the element (N, P, K, Ca and Al) economy of an Al-sensitive and an Al-tolerant wheat cultivar growing under different soil Al concentrations at field conditions. To reach this objective, two field experiments were conducted in an Andisol in Valdivia (39°47′18″S, 73°14′05″W), Chile. Treatments were a factorial arrangement of: (i) two spring wheat cultivars (Al-sensitive, Domo.INIA and Al-tolerant, Dalcahue.INIA) and (ii) five exchangeable Al levels (0-2.7 cmol₍₊₎ kg⁻¹) with three replicates. At harvest, plant biomass was sampled and divided into 5 organ categories: ears, grains, blade leaves, stems plus sheath leaves and roots. The element content (N, P, K, Ca and Al) in each organ was measured to quantify element uptake and concentration, nutrient uptake efficiency (UPE) and nutrient utilization efficiency (UTE). Element uptake (N, P, K, Ca, and Al) was negatively affected by the increased soil Al concentration in above-ground and root biomass in both cultivars (R² = 0.61-0.98, p < 0.01), although clear differences were found between cultivars. On the contrary, the impact of soil exchangeable Al on the plant element concentration was minor, showing weak associations with soil Al levels. However, the Al concentration in above-ground tissues of the Al-sensitive cultivar was an exception because it increased exponentially with the Al soil concentration (R² = 0.96-0.99, p < 0.001). Nutrient uptake efficiencies, UPEs (N, P, K and Ca), were negatively affected by soil Al concentrations and were well described by linear equations in both cultivars (R² = 0.58-0.98, p < 0.05), with notable differences between them. Both nutrient uptake (capture) and UPE were the traits that best explained above-ground biomass production (R² = 0.82-0.99, p < 0.001, n = 20). Nutrient utilization efficiency, UTEs (N, P, K and Ca) responded more conservatively to the soil Al concentration, except for the Al sensitive cultivar under very high soil Al levels.     

小麦田间测产和实际产量转换系数实证研究

小麦田间测产与实际产量的折算系数长期以来一直采用0.85,但是在近些年的实践中,发现实打验收和实收产量往往高于这一系数折算后的理论产量,导致在测产系数是否需要调整及调整幅度上颇存争议。为了深入探讨这一问题,利用连续7年的田间小区试验取样测产和实收产量结果,结合大田取样测产和实打收获案例,对田间取样测产和实收产量之间的转换系数(即测产系数)进行了系统计算和统计分析。结果表明,在使用实测千粒重进行产量估算时,测产系数平均为0.85,而使用常年千粒重时平均为0.92。由于千粒重不同年份间波动较大,因此建议在田间理论测产中使用当年实测千粒重时,折算系数采用0.85;使用常年千粒重时,测产系数采用0.90。