Internal and External Phosphorus Requirements for Optimum Grain Yield are Associated with P-utilization Efficiency of Wheat Cultivars

ABSTRACT

Considerable variation exists among wheat cultivars for phosphorus (P) acquisition and utilization to produce higher yields. We investigated critical P requirements for optimum grain yield of two wheat cultivars contrasting in P-use efficiency, i.e., NIA-Sunder (P-efficient) and NIA-Saarang (P-inefficient). Grain yield, P accumulation, and other P-efficiency relations of both cultivars increased with progressive addition of P, but at variable rates. NIA-Sunder exhibited higher grain yield, grain P concentration, harvest index, and P-use efficiency at all P levels as compared to NIA-Saarang. Internal P requirement for achieving 95% relative grain yield in NIA-Sunder and NIA-Saarang was obtained when P concentration in their grains was 4.07 and 3.48 mg g^?1 recorded at external P levels of 57.2 and 78.1 mg kg^?1 soil, respectively. Overall, NIA-Sunder accumulated 15% more grain P and required 27% less external P for attaining 95% relative yield than P-inefficient cultivar. Results suggested that internal and external P requirements aiming at optimum grain yield are associated with genotypic variations in wheat cultivars for P-utilization efficiency.     

Yield and Yield Components of Dry Bean Genotypes as Influenced by Phosphorus Fertilization

Dry bean is an important legume for South American population, and phosphorus (P) deficiency is the most yield-limiting nutrient for crop production in South American soils. A greenhouse experiment was conducted with the objective of evaluating influence of P fertilization on grain yield and yield components of 30 dry bean genotypes. The P levels used were 0 mg P kg^?1 (natural level of the soil) and 200 mg P kg^?1 applied with triple superphosphate fertilizer. Yield and yield components were significantly influenced with P as well as genotype treatments. The P?×?genotype interactions were significant for yield as well as yield components, indicating different responses of genotypes at two P levels. Root dry weight and maximum root length were also significantly increased with the addition of P fertilization. There were also significant differences among the genotypes in the growth of root system. Based on grain yield efficiency index (GYEI), genotypes were classified as P efficient, moderately efficient, and inefficient. Among 30 genotypes, 17 were classified as efficient, 12 were classified as moderately efficient, and 1 was classified as inefficient. Yield components such as pods per plant and seeds per pod were having significant positive association with grain yield. In addition, grain harvest index (GHI) was also having significant linear association with grain yield. Hence, it is possible to improve grain yield of dry bean in Brazilian Oxisol with the addition of adequate rate of P fertilization as well as use of P-efficient genotypes.     

Growth,yield and yield components of dry bean as influenced by phosphorus in a tropical acid soil

Phosphorus (P) deficiency is one of the most yield limiting factors for dry bean (Phaseolus vulgaris) production in tropical acid soils. Dry beans are invariably grown as mono-crops or as inter-crops under the perennial tropical crops. Information is limited regarding the influence of phosphorus fertilization on dry bean yield and yield components and P use efficiency in tropical acid soils. A greenhouse experiment was conducted to evaluate the influence of phosphorus fertilization on dry bean growth, yield and yield components and P uptake parameters. Phosphorus rates used were 0, 50, 100, 150, 200, and 250 mg P kg^?1 of soil. Soil used in the experiment was an acidic Inceptisol. Grain yield, shoot dry weight, number of pods, and 100 grain weight were significantly (P < 0.01) increased with phosphorus fertilization. Maximum grain yield, shoot dry matter, number of pods, and 100 grain weight were obtained with the application of 165, 216, 162, and 160 mg P kg^?1 of soil, respectively, as calculated by regression equations. Grain yield was significantly and positively associated with shoot dry weight, number of pods, P concentration in grain and total uptake of P in shoot and grain. Phosphorus use efficiency defined in several ways, decreased with increasing P rates from 50 to 250 mg P kg^?1 of soil. Maximum grain yield was obtained at 82 mg kg^?1 of Mehlich 1 extractable soil P. Results suggest that dry bean yield in Brazilian Inceptisols could be significantly increased with the use of adequate rates of phosphorus fertilization.     

Phosphorus Efficiency in Sunflower Cultivars and Its Relationships with Phosphorus,Calcium, Iron,Zinc and Manganese Nutrition

ABSTRACT

Phosphorus (P) efficiency (shoot dry weight at low P/shoot dry weight at high P) of a cultivar is the ability to produce a high yield in a soil that is limited in that element for a standard genotype. The large variation in P efficiency of different crops provides opportunities for screening crop species that perform well on low phosphorus soil. To explain the differences in P efficiency of sunflower (Helianthus annuus L.) cultivars a glasshouse pot experiment was conducted by using P-deficient soil [0.5 M sodium bicarbonate (NaHCO₃)-extractable P 8.54 mg kg^?1] treated with 0 (low P) and 100 mg P kg^?1 soil (high P). The relationship between P efficiency and P, calcium (Ca), iron (Fe), zinc (Zn), and manganese (Mn) nutrition and anthocyanin accumulation was investigated in ten sunflower cultivars. Phosphorus deficiency resulted in significant decreases in the shoot and root yield. Phosphorus-efficient cultivars have the ability to produce higher yield than the inefficient cultivars in a limited P conditions. Our results showed that P-efficient cultivars had lower P concentrations, but higher P content in low P conditions. Phosphorus-efficient cultivars also have lower Ca and Fe concentrations in low P conditions but not in P-sufficient conditions. Applied P resulted in significant decreases in Zn concentrations in the shoots of the cultivars. Anthocyanin concentrations showed an accumulating pattern in all cultivars under P deficiency. The results demonstrated that phosphorus efficiency of the sunflower cultivars depends on their ability to produce higher yield and take up more P, and lower the concentration of Ca and Fe in shoots under low P conditions.     

施磷量对不同磷效率小麦氮、磷、钾积累与分配的影响

在土培盆栽条件下,以磷高效小麦(CD1158-7、省A3宜03-4)和磷低效小麦(渝02321)为材料,研究了不施磷、施磷(P)10、20和30mg/kg对小麦不同生育时期生物量、籽粒产量及氮、磷、钾的积累与分配的影响。结果表明:(1)随施磷量的减少,不同磷效率品种小麦籽粒产量和生物量均减少;同一施磷处理,磷高效品种籽粒产量和生物产量高于磷低效基因型。不施磷、施磷10mg/kg,高效品种CD1158-7、省A3宜03-4的籽粒产量为低效品种渝02321 的1.84 倍和1.74倍、1.64倍和1.27倍。(2)低磷处理,磷高效品种小麦植株能够积累较多的氮素;扬花期之前,磷高效品种氮素积累量占小麦全生育期积累量的比例高于低效品种。拔节期、孕穗期氮素分配比例为叶>茎>根,扬花期为叶>茎>穗>根,而成熟期为籽粒、颖壳>茎>叶>根。拔节期和孕穗期磷高效品种根的氮素分配比例高于低效品种,而扬花期和成熟期磷高效品种穗(籽粒)氮素分配比例较高。(3)小麦植株磷素积累量主要集中在拔节期以后的生育时期,占全生育期的82.32%~94.23%。低磷处理,高效品种在拔节期和孕穗期磷素积累量高于低效品种,孕穗期尤为突出。扬花期之前,不施磷处理下,磷高效品种根的磷素分配比例较高。(4)不同施磷处理下,拔节期、孕穗期及扬花期,磷高效品种小麦的钾积累量高于低效品种。不同器官钾素分配比例拔节期和孕穗期均为叶>茎>根,扬花期为茎>叶>穗>根,成熟期为茎>叶>籽粒、颖壳>根。磷高效品种在颖壳和籽粒的钾素分配比例高于低效品种。     

Evaluating the performance of mungbean genotypes for grain yield,phosphorus accumulation and utilization efficiency

Ten mungbean (Vigna radiata R. Wilczek) genotypes were evaluated for grain yield and phosphorus (P) efficiency at adequate and deficient P in soil. Genotypes differed significantly in plant height, grain yield, P accumulation (PA), and other P-efficiency parameters at both P levels. The genotype “AEM-40/30” had maximum plant height, grain yield, and phosphorus physiological efficiency index (PPEI) under P deficiency. The genotypes were distributed into nine groups based on their relationship between total PA and grain yield at deficient P level. Moreover, genotypes were categorized into low, medium, or high efficient for each parameter by allotting index score (1, 2, or 3). Maximum cumulative index score (25) was attained by the genotypes “AEM-40/30 and AEM-20/3/87”, and genotype “AEM-30/5/8/90” scored least total index (14). The significant differences among mungbean genotypes for PA, phosphorus harvest index (PHI), PPEI, and grain yield can be exploited to select or identify P-efficient mungbean genotypes.     

DRY BEAN GENOTYPES EVALUATION FOR GROWTH,YIELD COMPONENTS AND PHOSPHORUS USE EFFICIENCY

Dry bean along with rice is a staple food for the population of South America. In this tropical region beans are grown on Oxisols and phosphorus (P) is one of the most yield limiting factors for dry bean production on these soils. A greenhouse experiment was conducted to evaluate P use efficiency in 20 elite dry bean genotypes grown at deficient (25 mg P kg^?1 soil) and sufficient (200 mg P kg^?1) levels of soil P. Grain yields and yield components were significantly increased with P fertilization and, interspecific genotype differences were observed for yield and yield components. The grain yield efficiency index (GYEI) was having highly significant quadratic association with grain yield. Based on GYEI most P use efficient genotypes were CNFP 8000, CNFP 10035, CNFP10104, CNFC 10410, CNFC 9461, CNFC 10467, CNFP 10109 and CNFP 10076 and most inefficient genotypes were CNFC 10438, CNFP 10120, CNFP 10103, and CNFC 10444. Shoot dry weight, number of pods per plant, 100-grain weights and number of seeds per pod was having significant positive association with grain yield. Hence, grain yield of dry bean can be improved with the improvement of these plant traits by adopting appropriate management practices. Soil pH, extractable P and calcium (Ca) saturation were significantly influenced by P treatments. Based on regression equation, optimum pH value in water was 6.6, optimum P in Mehlich 1 extraction solution was 36 mg kg^?1 and optimum Ca saturation value was 37% for dry maximum bean yield.     

Influence of pH on Productivity,Nutrient Use Efficiency by Dry Bean,and Soil Phosphorus Availability in a No‐Tillage System

Abstract

Low pH is one of the most yield‐limiting factors for crop production in Cerrado soils. The objective of this study was to determine influence of soil pH on grain yield and its components, and use of nutrients by dry bean in a no‐tillage system in an Oxisol (Typic Haplorthox) of the Cerrado region of Brazil. Five field experiments were conducted for three consecutive years. The pH levels were low (5.3), medium (6.4), and high (6.8), created by applying lime at the rates of 0, 12, and 24 Mg ha^?1. Grain yield and its components were significantly influenced by soil pH. Adequate pH for grain yield and its components was 6.4. Maximum variation in grain yield was measured by shoot dry weight, and minimum variation was due to 100‐grain weight. Nutrient utilization efficiency was in the order of magnesium (Mg) > phosphorus (P) > calcium (Ca) > potassium (K) > nitrogen (N) > copper (Cu) > manganese (Mn) > zinc (Zn) > iron (Fe). Soil extractable P increased linearly with increasing pH in the range of 5.3 to 7.3. These results show that adequate soil pH is an important soil acidity index in improving bean yield in Brazilian Oxisols.     

Phosphorus Nutrition of Lowland Rice in Tropical Lowland Soil

Rice is a main food crop for about half of the world's population, and phosphorus (P) is the main limiting nutrient in rice production in tropical lowlands. A greenhouse experiment was conducted to evaluate P requirements of lowland rice grown on a lowland soil (Inceptisol). Dry matter, grain yield, and yield-attributing characteristics were significantly (P < 0.01) influenced by P fertilization. Based on quadratic response, maximum shoot dry weight and grain yield were obtained with the application of 190 mg P kg^?1 of soil. Maximum panicle, tiller number, and plant height were obtained with the application of 177 192, and 175 mg P kg^?1 of soil, respectively. Mehlich 1–extractable P for maximum grain yield was 15.6 mg kg^?1 of soil. Variability in grain yield with plant growth and yield parameters was in the order of tiller > shoot dry weight > panicle number > spikelet sterility > plant height > grain harvest index > panicle length > weight of 1000 grains. Phosphorus uptake in shoot and concentration and uptake in grain significantly (P < 0.01) increased grain yield. However, variability in grain yield was greater with concentration and uptake of P in the grain. Similarly, P harvest index was also significantly associated with grain yield. Agronomic P-use efficiency, apparent P-recovery efficiency, and P-utilization efficiency decreased quadratically with increasing P rates, whereas physiological P-use efficiency increased quadratically and agrophysiological P-use efficiency decreased linearly with increasing P rates. Agrophysiological and utilization P-use efficiencies had significant positive correlation with grain yield.     

Nutrient Uptake in Dry Bean Genotypes

Dry bean is an important legume for human consumption in South America. A greenhouse experiment was conducted to evaluate uptake and use efficiency of macro- and micronutrients by six dry bean genotypes at two P levels (25 and 200 mg kg^?1 soil). Shoot dry weight and grain yield varied significantly among genotypes and significantly increased with increasing phosphorus (P) levels. Grain harvest index (GHI) and 100-grain weight also differ significantly among genotypes and significantly increased with the increasing P levels. Based on grain yield efficiency index (GYEI), genotypes were classified as efficient and inefficient. The most efficient genotype was CNFP 10104, and inefficient genotypes were CNFP 10103 and CNFP 10120. Number of pods per plant and number of seeds per pod increased significantly with the addition of 200 mg P kg^?1 of soil compared to the low level of P (25 mg P kg^?1). Similarly, nitrogen (N), P, calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn), copper (Cu), and manganese (Mn) concentrations and uptake in the shoot and grain also significantly varied among genotypes. Uptake of macro- and micronutrients was greater under the greater P rate compared to the low P rate. This may be related to greater shoot or grain yield at 200 mg P kg^?1 soil compared to 25 mg P kg^?1 of soil.     

Identification of Phosphorous Efficient Germplasm in Oilseed Rape

ABSTRACT

Plant species and genotypes within one species may significantly differ in phosphorus (P) uptake and utilization when they suffer from P starvation. The objective of this research was to screen P-efficient germplasm of oilseed rape (Brassica napus L.) and analyze the possible mechanism responsible for P efficiency by two-steps screening experiments and validation of P efficiency. Phosphorus efficiency coefficient at seedling stage, namely, ratio of shoot dry weight under low P to that under adequate P (PECS) of 194 oilseed rape cultivars varied from 0.050 to 0.62 and was significantly related with shoot dry weight under low P level (r = 0.859??, P < 0.01). Oilseed rape cultivar ‘Eyou Changjia’ presented the highest P efficiency coefficient in each growth stage and had the highest seed yield at low P, whereas oilseed rape cultivar ‘B104-2’ was the most sensitive to low P stress among the 12 candidate cultivars obtained from the two-steps screening experiments. Under low P condition in validation experiments of soil and solution cultures, ‘Eyou Changjia’ could produce much more dry matter and acquire more P than ‘B104-2.’ Moreover, P efficient coefficient obtained from the pot experiment was comparable to those from the field experiment. This might be attributed to high P uptake efficiency for ‘Eyou Changjia’ when it suffered from low-P stress. Comparison of results from the hydroponics with those from the pot and field experiments led to the conclusion that the P uptake efficiency in the hydroponics is highly related to that in soil culture conditions. These results show that there are large genotypic differences in response to phosphorus deficiency in oilseed rape germplasm (Brassica napus L.) and ‘Eyou Changjia’ is P-efficient and ‘B104-2’ is P-inefficient. By comparing these results further, the mechanism responsible for P efficiency was suggested to be mainly due to high P uptake efficiency by forming larger root system, and improving the ability of mobilizing and acquiring soil P in P-efficient oilseed rape under the condition of P starvation.     

Phosphorus Use Efficiency in Upland Rice Genotypes Under Field Conditions

Phosphorus (P) deficiency is one of the most yield limiting factors for crop production in South American soils. Upland rice (Oryza sativa L.) is an important crop in South American cropping systems, including Brazil. A field experiment was conducted with the objective to evaluate 20 upland rice genotypes for phosphorus (P) use efficiency. The P rate used was low (0 kg P ha^?1) and high [87 kg P ha^?1 or 200 kg phosphorus pentoxide (P₂O₅) ha^?1]. Plant height, shoot dry weight, grain yield, panicle number, 1000 grain weight, spikelet sterility, and grain harvest index were significantly influenced by P and genotype treatments. The P X genotype interaction was significant for grain yield, indicating that genotypes responded differently under two P rates. Overall, grain yield increased by 12% with the addition of P fertilization. Based on grain yield efficiency index, genotypes were classified into efficient, moderately efficient, and inefficient group. The genotypes that were classified as efficient in P use were BRA032048, BRA042094, BRA02601, BRA032051, BRA032033, BRA052015, BRA042156, BRA01600, BRA01506, BRA052023 and BRA042160. The inefficient genotypes in P us efficiency were BRS Primavera, BRA052045, BRA01596, and BRS Sertaneja. Grain harvest index had a significant positive association with grain yield and spikelet sterility had a significant negative association with grain yield, as expected. Average, P-use efficiency of five genotypes was about 17 kg kg^?1 (kg grain yield per kg P applied).     

Differential Soil Acidity Tolerance of Dry Bean Genotypes

Soil acidity is a major yield-limiting factors for bean production in the tropical regions. Using soil acidity–tolerant genotypes is an important strategy in improving bean yields and reducing cost of production. A greenhouse experiment was conducted with the objective of evaluating 20 dry bean genotypes for their tolerance to soil acidity constraints. An Inceptisol soil was amended with dolomitic lime (2 g dolomitic lime kg^–1 soil) to achieve low acidity (pH = 5.9) and without lime (zero lime kg^–1 soil,) to achieve high acidity (pH = 4.8) levels to evaluate bean genotypes. At both acidity levels, genotypes differed significantly in shoot dry weight and grain yield. Shoot dry weight and grain yield were significantly decreased at the high acidity level compared to the low acidity level. Grain yield was more sensitive to soil acidity than shoot dry weight. Hence, grain yield was used in determination of tolerance index (GTI) to differentiate the range of soil acidity tolerance among bean genotypes. Based on a GTI value, 55% of the genotypes were classified as tolerant, 40% classified as moderately tolerant, and the remaining were grouped as susceptible to soil acidity. The genotype CNFC 10410 was most tolerant and genotype CNFP 10120 was most susceptible to soil acidity. Number of pods and grain harvest index were significantly and positively associated with grain yield. The improvement in grain yield in low acidity may be related to reduction of toxic levels of soil aluminum (Al³⁺) and hydrogen (H⁺) ions by lime addition. At harvest, soil extractable phosphorus (P) and potassium (K) increased with the reduction of soil acidity, and this might have contributed to the better nutrition of beans and lead to higher growth.     

Dry matter accumulation and phosphorus efficiency response of cotton cultivars to phosphorus and drought

Low soil phosphorus (P) availability and drought are the most recognized growth-limiting factors for the cotton production in arid regions. A pot experiment with P-efficient (Xinluzao19, X19) and P-inefficient (Xinluzao19, X26) cotton cultivars was conducted to investigate the effects of P and drought on dry matter accumulation and P efficiency. Results showed that biomass and chlorophyll content of leaves increased significantly with the increase in soil P content, whereas the root:shoot ratio decreased dramatically. Drought increased the root:shoot ratio, but the chlorophyll content of leaves remained stable. The yield of X19 increased with the increase in soil P content. For X26, the highest yield was attained under the medium P content. Under drought conditions, root P efficiency ratio, P absorption efficiency, and P transfer efficiency were all proportional to P concentration, whereas P utilization was inversely proportional. Compared with X26, X19 presented higher P absorption efficiency and P utilization but lower root P efficiency ratio and P transfer efficiency. It suggested thatthe application of phosphate fertilizer under drought could increase the root P efficiency ratio, P absorption efficiency, and P transfer efficiency, thereby enhancing the ability of stress resistance of cotton and significantly increasing biomass as well as cotton yield.     

POTASSIUM-USE EFFICIENCY IN COMMON BEAN GENOTYPES

Potassium (K) is one of the most important nutrients limiting yield of common bean in South America. Use of K-efficient crop genotypes along with K fertilizer may be a viable strategy to improve yield and reduce cost of production. A greenhouse experiment was conducted to evaluate K-use efficiency of 10 promising genotypes of common bean (Phaseolus vulgaris L.). The genotypes were grown on an Oxisol at 0 mg K kg^?1 (low K) and 200 mg K kg^?1 (high K) of soil. Shoot dry weight, grain yield, number of pods, number of grains, 100-grain weight, grain harvest index, and K harvest index were significantly (P < 0.01) affected by level of K as well as genotype, except for the number of pods by genotype. Significant genotypic differences in K-use efficiency were found. On the basis of K-use efficiency (mg grain weight/mg K accumulated in shoot and grain), genotypes were classified as efficient and responsive (ER), efficient and nonresponsive (ENR), nonefficient and responsive (NER), and non-efficient and non-responsive (NENR). Only genotype Diamante Negro was only classified as ER, and genotypes Carioca, Pérola, Rosinha G-2, and Xamego were classified as ENR. Genotypes LM93300166 and LM93300176 were in the group NER, and in the NENR group were genotypes Iraí, Jalo Precoce, and Novo Jalo. From a practical point of view, genotypes which produce high grain yield at a low level of K and respond well to added K are the most desirable because they are able to express their high yield potential in a wide range of K availability.     

GENOTYPIC DIFFERENCES IN ROOT MORPHOLOGY AND PHOSPHORUS UPTAKE KINETICS IN BRASSICA NAPUS UNDER LOW PHOSPHORUS SUPPLY

Application of phosphorus (P) fertilizer is important in crop production because of the low bioavailability of phosphorus to plants in both acidic and calcareous soils. Although rapeseed (Brassica napus) is generally sensitive to P deficiency, different cultivars differ widely in this respect. Differences in P uptake and utilization between two rapeseed cultivars, one P-efficient (‘97081’) and one P-inefficient (‘97009’), were evaluated in solution culture by studying the changes in root morphology and parameters of P uptake kinetics in response to low-P stress. The P-efficient cultivar had lower Km and Cmin values and higher Vmax and developed longer and denser lateral root hair with greater number of root tips and branches under low-P stress, which resulted in a better developed root system and more efficient uptake of P. That, in turn, led to higher concentration and accumulation of P in the plants, culminating in higher biomass production. However, P utilization efficiency (biomass production per unit P accumulated in plant) of the P-efficient ‘97081’ was lower than that of ‘97009’ when P was deficient. These results suggest that P efficiency in rapeseed is due to a better developed root system as well as efficient uptake of P.     

Response of common bean varieties to the magnesium application in the tropical soil

The appropriate supply of magnesium (Mg) to the common bean (Phaseolus vulgaris L.) according to the requirements of each variety increases the productivity and nutritional value of grains. However, there are few studies on soil's ability to provide the adequate amount of the nutrient and on the reaction of plants with different Mg concentrations. The present study analyzed the response of the common bean plant to soil fertility, grain yield (GY), shoot dry weight (SDW) yield, nutritional status and the response of physiological components of the plant to the concentrations of Mg applied to the tropical soil. Thus, an experiment was conducted in a completely randomized design, in 5 × 4 factorial arrangement, with three replicates. The varieties BRS Estilo, IAPAR 81, BRS Ametista, IPR Campos Gerais (CG) and IPR Tangará were cultivated in an Ustoxix Quatzipsamment with five rates of Mg [0, 50, 100, and 200 mg kg^?1, source magnesium chloride (MgCl₂)]. The common bean varieties and the Mg rates significantly affected the soil chemical properties. Photosynthetic rate, stomatal conductance, transpiration rate, intercellular concentration of carbon dioxide (CO₂), and total soluble sugars significantly correlated with common bean GY and SDW yield. The nutrient content in leaves and grains showed difference responses among the varieties. IAPAR 81 showed the highest rate of mobilization of nitrogen, phosphorus, magnesium, sulfur, boron, copper and zinc (N, P, Mg, S, B, Cu, and Zn) for grains, being an important factor in studies of crop biofortification.     

Selection Criteria for Genotypes and Identification of Plant Characteristics for Phosphorus-Efficient Wheat

Most genetic analyses of wheat crops concentrate on elucidating the mode of inheritance of plant characteristics. However, it is equally important to study the genetic relationship between different characteristics so that the consequences of selection for one characteristic on the performance of another can be predicted. Three field experiments with 15 wheat genotypes were conducted at two sites with similar soil types and agroecological conditions (two experiments at site 1 and one experiment at site 2) to evaluate wheat genotypes through correlation and path analyses for identification of plant characteristics responsible for high grain yield at low phosphorus (P) (7.86–8.23 mg P kg^?1 soil; control, no application of P) and adequate P (52 kg P ha^?1) in soil. On the average of the three experiments, the genotypic and phenotypic coefficients in correlation analysis agreed closely in each case. Relatively high values of genotypic coefficient showed a masking influence of genetic factors in the grain production. Grain yield correlated significantly with P-uptake parameters, such as P uptake in grain and straw. Integration of P in grain formation varied among wheat genotypes because of differences in their abilities to absorb, translocate, distribute, accumulate, and utilize P. The integrated effect of these physiological processes appeared in the form of end product (i.e., grain). The yield potential of a genotype to produce grain can be measured directly from absolute grain yield, but when selection was made through the involvement of plant factors such as harvest index, it proved to be a good predictor of grain yield. Positive relationship of harvest index with grain yield indicated an increase in grain yield. Because grain production is an outcome of the integrated effect of many P-related physiological processes, P efficiency was measured by P harvest index, P efficiency ratio, and P physiological efficiency index. The P physiological efficiency index was found to be an appropriate measure of P-use efficiency. When the selection was made through path analysis, it was observed that the genotypes that had high harvest index, absorbed more P, accumulated more P in grain, and produced more grain per unit of absorbed P were efficient in P use and produced high grain yield under low available soil P field conditions. Wheat genotypes ‘Inqlab 91,’ ‘Pak 81,’ ‘4072,’ ‘4943,’ and ‘5039’ were capable of producing high grain yield under low soil P field conditions in this study.     

控释复肥中磷素在马铃薯上的效应研究

采用18-9-18和15-15-15包膜控释肥及相应的普通速效复合肥进行马铃薯小区试验,研究在低磷(P2O575kg/hm2)和高磷(P2O5150kg/hm2)2种磷肥水平下,磷素控释对土壤供磷状况、马铃薯磷素累积、当季磷肥利用率以及产量的影响。研究结果表明,与普通速效复肥相比,控释复肥施入土壤后磷的有效性较高,马铃薯植株的磷累积吸收量比普通化肥明显增加,当季磷肥利用率显著提高。低磷控释的处理当季磷肥利用率比非控释的处理增加了32个百分点,达到了44.4%;高磷控释肥处理的当季磷肥利用率比高磷非控释的处理增加了35个百分点,达到了48.7%,并且显著提高了马铃薯产量。     

Rice and common bean growth and nutrient concentration as influenced by aluminum on an acid lowland soil

Aluminum (Al) toxicity is a major limiting factor for crop production in many acid soils in Brazil. Two greenhouse experiments were conducted to evaluate response of rice (Oryza saliva L.) and common bean (Phaseolus vulgaris L.) to Al levels on a Low Humic Gley acid soil. The Al levels created by liming were: 0,0.03, 0.10, 0.23, 1.03, and 3.83 cmol_c kg^‐1 of soil. Rice dry matter and grain yield were significantly improved (P<0.05) with increasing Al levels in the soil solution. However, common bean dry matter as well as grain yield were significantly (P<0.01) decreased with increasing Al levels. At 3.83 cmol_c Al kg^‐1 of soil, bean did not produce any dry matter or grain yield. On an average, Al decreased nutrient concentrations in the tops of rice plant except zinc (Zn) and manganese (Mn), but in bean crop almost all the nutrients concentrations were increased with increasing Al levels. Rice showed tolerance to Al toxicity, whereas, common bean was susceptible to toxicity of this element. For successful intensive crops production lime application will be necessary in Varzea soils especially for legume production.