Yield and Yield Components and Phosphorus Use Efficiency of Lowland Rice Genotypes

Phosphorus deficiency is main constraints for lowland rice production in various rice producing regions of the world. A greenhouse experiment was conducted using lowland (Inceptisol) soil with the objective to determine response of seven lowland rice (Oryza sativa L.) genotypes to phosphorus fertilization and to evaluate their phosphorus (P) use efficiency. Phosphorus treatments included control (0 mg P kg^?1) and 200 mg P kg^?1 of soil. Plant height and shoot dry weight were significantly (P < 0.001) influenced by P treatments. Phosphorus X genotypes interaction was significant for shoot dry weight, indicating different response of genotypes under two P levels. At low P level, none of the genotypes produced grain yield, indicating original P level in the soil was too low for lowland rice yield. However, genotypes differed significantly in grain yield at high P level. Panicle number, panicle length, and thousand grains weight had a significant quadratic association with grain yield. However, spikelet sterility had a significant linear negative association with grain yield. The P use efficiency expressed as agronomic efficiency (AE), physiological efficiency (PE), agro-physiological efficiency (AP), apparent recovery efficiency (ARE), and utilization (UE) were significantly different among genotypes. These efficiencies were having significantly positive association with grain yield, with exception to ARE, indicating improving grain yield with improved P use efficiencies in rice.     

Liming and Cultivars Affect Root Growth,Nodulation, Leaf to Stem Ratio,Herbage Yield,and Elemental Composition of Alfalfa on an Acid Soil

Abstract

Soil acidity is one of the limiting factors affecting the production and sustainability of pastures and crops in many parts of the world. An on‐farm experiment was conducted in Australia to investigate the cultivar variation in alfalfa (lucerne) (Medicago sativa L.) with respect to soil acidity and response to applied lime. The experimental site was a brown sandy clay loam with a soil pH of 4.8 (1:5 calcium chloride). Ten cultivars (Hunter River, Hunterfield, Sceptre, Aurora, Genesis, Aquarius, Venus, PL90, PL55, and breeding line Y8804) were tested at two levels of lime (0 and 2 t ha^?1). Lime application significantly increased the root growth, nodulation, leaf retention, leaf to stem ratio, herbage yield, and crude protein content of alfalfa. Liming had a significant effect on elemental composition of alfalfa shoots. Aluminum (Al) concentration was reduced from 93 mg kg^?1 DM in nil lime treatment to 45 mg kg^?1 DM in +lime treatment. Similarly, manganese (Mn) and iron (Fe) shoot concentrations were reduced from 74 mg kg^?1 DM and 92 mg kg^?1 DM to 59 mg kg^?1 DM and 76 mg kg^?1 DM, respectively. Liming significantly improved the calcium (Ca) concentration of shoots, while there was a little effect on phosphorus (P) and zinc (Zn) concentrations of alfalfa shoots. Cultivars had differential response to lime application. Response to lime application was greater in Y8804 and Aurora alfalfa where yield increased by 32% and 31%, while yield increase was 11–22% in other cultivars. Cultivars also differed significantly in root growth, nodulation, leaf drop, leaf to stem ratio, crude protein content, and elemental composition of shoots. Cultivars with better performance in no liming treatment had comparatively lower shoot Al, Mn, and Fe concentrations compared with other cultivars.     

Cadmium Uptake by Winter Wheat Seedlings in Response to Interactions Between Phosphorus and Zinc Supply in Soils

ABSTRACT

Effects of application of zinc (Zn) (0, 1, 5, 10 mg kg^?1 soil) and phosphorus (P) (0, 10, 50, 100 mg kg^?1 soil) on growth and cadmium (Cd) accumulations in shoots and roots of winter wheat (Triticum aestivum L.) seedlings were investigated in a pot experiment. All soils were supplied with a constant concentration of Cd (6 mg kg^?1 soil). Phosphorus application resulted in a pronounced increase in shoot and root biomass. Effects of Zn on plant growth were not as marked as those of P. High Zn (10 mg kg^?1) decreased the biomass of both shoots and roots; this result may be ascribed to Zn toxicity. Phosphorus and Zn showed complicated interactions in uptake by plants within the ranges of P and Zn levels used. Cadmium in shoots decreased significantly with increasing Zn (P < 0.001) except at P addition of 10 mg kg^?1. In contrast, root Cd concentrations increased significantly except at Zn addition of 5 mg kg^?1 (P < 0.001). These results indicated that Zn might inhibit Cd translocation from roots to shoots. Cadmium concentrations increased in shoots (P < 0.001) but decreased in roots (P < 0.001) with increasing P supply. The interactions between Zn and P had a significant effect on Cd accumulation in both shoots (p = 0.002) and roots (P < 0.001).     

Interaction Between Phosphorus Nutrition and Drought on Grain Yield,and Assimilation of Phosphorus and Nitrogen in Two Soybean Cultivars Differing in Protein Concentration in Grains

ABSTRACT

Drought affects many physiological and biochemical processes and thus reduces plant growth. Phosphorus (P) fertilization improves tolerance to drought stress in many plants. A greenhouse experiment examined the interactive effects of P nutrition and drought stress on P accumulation and translocation, yield, and protein concentration in grains of two cultivars of soybean [Glycine max (L.) Merr.]. Plants of cultivars ‘Heisheng 101’ (high protein in grains) and ‘Dongnong 464’ (low protein) were grown in a P-deficient soil supplied with 0–30 mg P kg^?1 soil. Drought stress was imposed at the initial flowering (R1) or the podding (R4) stage. Drought stress limited P accumulation and reduced P translocation to the seed. The addition of P enhanced the concentration and accumulation of nitrogen (N) and P in shoots and seeds of both cultivars. Drought stress decreased shoot biomass, grain yield, and P accumulation; the decrease was greater in ‘Dongnong 46’ than ‘Heisheng 101,’ and even more so if drought stress was imposed at R4 than at R1. In contrast, drought stress increased the concentration of N in shoot and protein in grains. The addition of P alleviated the effect of drought stress on plant growth, P accumulation, and grain yield in both cultivars but to a greater extent in ‘Dongnong 46’. The results suggest that application of P fertilizers could mitigate drought stress at the reproductive stage, resulting in less yield penalty and improvement of grain quality of soybean grown in P-deficient soils.     

Zinc Tolerance in Wheat Cultivars as Affected by Varying Levels of Phosphorus

Abstract

The effect of zinc–phosphorus (Zn‐P) interaction on Zn efficiency of six wheat cultivars was studied. The higher dry matter yields were observed when Zn was applied at 5 µg g^?1 soil than with no Zn application. Phosphorus applications also increased dry matter yield up to the application of 25 µg P g^?1 soil. The dry matter yield was significantly lower at the P rate of 250 µg g^?1 soil. At the Zn‐deficient level, the Zn‐efficient cultivars had higher Zn concentrations in the shoots. Zinc concentrations in all cultivars increased when the P level in the soil was increased from 0 to 25 µg P g^?1 soil except for the cv. Durati, in which Zn concentrations decreased with increases in P levels. However, when Zn×P interactions were investigated, it was observed that at a Zn‐deficient level, Zn concentrations in the plant shoot decreased with each higher level of P, and more severe Zn deficiency was observed at P level of 250 µg g^?1 soil.     

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.     

Lead and Zinc Extraction Potential of Two Common Crop Plants, Helianthus Annuus and Brassica Napus

Phytoextraction is a remediation technology that uses plants to remove heavy metals from soil. The success of a phytoextraction process depends on adequate plant yield (aerial parts) and high metal concentrations in plant shoots. A pot experiment was conducted to investigate the combination effects of plants [sunflower (Helianthus annuus) and canola (Brassica napus)] with soil treatments (manure, sulfuric acid and DTPA). Treatments, including two plants and seven soil treatments, which applied according to completely randomized factorial design with three replications. The largest shoot dry weight biomass production occurred in manure treatments for both plants. The maximum shoot concentrations of Pb and Zn were 234.6 and 1364.4 mg kg^?1 respectively in three mmoles DTPA kg^?1 treatment of sunflower. Furthermore the results showed that sunflower had a higher extracting potential for removal of Pb and Zn from polluted soil.     

Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

Upland rice genotypes evaluation for phosphorus use efficiency

Phosphorus (P) deficiency is one of the most important yield‐limiting factors in acid soils in various parts of the world. The objective of this study was to evaluate the growth and P‐use efficiency of 20 upland rice (Oryza sativa L.) genotypes at low (0 mg P kg^‐1), medium (75 mg P kg^‐1), and high (150 mg P kg^‐1) levels of applied P on an Oxisol. Plant height, tillers, shoot and root dry weight, shoot‐root ratio, P concentration in root and shoot, P uptake in root and shoot, and P‐use efficiency were significantly (P<0.01) affected by level of soil P as well as genotype. Shoot weight and P uptake in shoot were found to be the plant parameters most sensitive to P deficiency, suggesting that these two parameters may be most suitable for screening rice genotypes for P‐use efficiency under greenhouse conditions.     

Relative Phosphorus Utilization Efficiency,Growth Response,and Phosphorus Uptake Kinetics of Brassica Cultivars under a Phosphorus Stress Environment

Abstract

Plants grown in highly weathered or highly alkaline calcareous soils often experience phosphorus (P) stress but never a P‐free environment. Thus, applications of mineral P fertilizers are often required to achieve maximum yield, but recovery of applied P fertilizers is notoriously low. Phosphorus deprivation elicits a complex array of morphological, physiological, and biochemical adaptations among plant species and genotypes to enhance P acquisition and utilization efficiency. Ten Brassica cultivars were grown hydroponically to investigate their relative efficiency to utilize deficiently (20‐µM) and adequately (200‐µM) supplied P, using Johnson's modified solution. Cultivars differed significantly (P<0.001) in biomass accumulation. Orthophosphate concentration and uptake in shoot and root, absolute and relative growth rate, and P‐utilization efficiency (PUE) were also significantly different among various Brassica cultivars. Root‐shoot ratio and specific absorption rate were substantially increased in plants subjected to low P supply. Shoot and root dry‐matter yield as well as total biomass production correlated significantly (P<0.01) with their total P uptake and PUE. Cultivars, which were efficient in P utilization, were also efficient accumulators of biomass under adequate as well as deficient levels of P supply. As part of the study, kinetic parameters of P uptake were evaluated for six contrasting Brassica cultivars in PUE, grown in nutrient solution. The kinetic parameters related to P influx were maximal transport rate (Vmax), the Michaelis–Menten constant (Km), and the external concentration when net uptake is zero (Cmin). Lower Km and Cmin values were indicative of P‐uptake ability of the cultivars, evidencing their adaptability to P‐stress conditions. In another experiment, six cultivars were exposed to no P nutrition for 27 days after initial feeding on optimum nutrition for 14 days. All the cultivars retranslocated P from aboveground parts to their roots during growth in P‐free conditions, the magnitude of which was variable in different cultivars. Phosphorus concentration at 41 days after transplanting was higher in developing leaves than developed leaves. Translocation of absorbed P from metabolically inactive sites to active sites in plants growing under P‐stress conditions may have helped the tolerant cultivars to establish a better rooting system, which provided basis for tolerance against P‐deficiency stress and increased PUE.     

Combined Effect of Arsenic and Phosphorus on Mineral Element Concentrations of Sunflower

This study was undertaken to examine the combined effect of soil‐applied phosphorus (P) and arsenic (As) on P, As, potassium (K), calcium (Ca), magnesium (Mg), silicon (Si), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), titanium (Ti), rubidium (Rb), strontium (Sr), barium (Ba), lantanium (La), and cerium (Ce) concentrations of sunflower plants under glasshouse conditions determined by polarized‐energy‐dispersive x‐ray fluorescence (PEDXRF). Three levels of As (0, 30, and 60 mg kg^?1) and four levels of P (50, 100, 200, and 400 mg kg^?1) were applied to soil‐grown plants. Increasing levels of both As and P significantly increased As concentrations in the plants. Plant growth was significantly reduced with increased As supply regardless of applied P levels. Arsenic toxicity caused significant increases in the concentrations of Mn, La and Ce, but it decreased K, Ca, Mg, Si, Fe, Zn, Cu, Rb, and Sr concentrations. Applied P increased the concentrations of Ti, Sr, and Ba and decreased Zn and Cu. In conclusion, the use of P fertilizers in As‐contaminated soils should be carefully considered in respect to increased As, Ti, Sr, and Ba availability and reduced Zn and Cu availability.     

Compared Phosphorus Efficiency in Soybean,Sunflower and Maize

ABSTRACT

A more comprehensive understanding of the mechanisms of phosphorus (P) efficiency is agronomically significant to advance in the design of crop management schemes that increase P efficiency and reduce the need of fertilizers. Phosphorus efficiency is defined as the ability of a plant to acquire P from the soil and/or to utilize it in the production of biomass or the harvestable organ. Because most parameters related to P efficiency vary according to the growth conditions and isolation of the individual effect of P efficiency is not straightforward; plants must be grown in uniform experimental conditions to obtain a fair comparison of their nutrient acquisition and utilization. In this work, we compare the ability of soybean, sunflower, and maize to utilize and acquire soil P. Field and greenhouse experiments including different P levels were conducted. The general observation was that the three species ranked differently according to the specific parameter of P efficiency considered. Maize clearly showed higher P utilization efficiency than soybean and sunflower, either expressed as biomass or as grain produced per unit of absorbed P. In turn, soybean and sunflower exhibited higher acquisition efficiency than maize. Soybean showed the shallowest root system: 69% of the total root length was concentrated in the top 20 cm of the soil. Phosphorus uptake per unit root length was rather similar among the three species, but soybean and sunflower had higher P uptake per unit of root weight. This can be explained by the higher specific root length (SRL) and specific root area (SRA) of both dicots. For example, SRL averaged 59, 94, and 34 m g^?1 in field grown soybean, sunflower, and maize, respectively. The more favorable root morphology determined that soybean and sunflower can explore more soil with the same belowground biomass and absorb more P per unit of carbon invested belowground. Since the three species exhibited similar values of P uptake per unit root length, we hypothesize that the capacity of each segment of root to deplete soil P fractions is similar.     

Genetic Variations of Brassica Cultivars for P Acquisition in a P Stress Environment and Comparison of P Sources for Sustainable Crop Management

To compare the growth performance of Brassica in a phosphorus (P) stress environment and response to added P, six Brassica cultivars were grown in pots for 49 days after sowing, using a soil low in P [sodium bicarbonate (NaHCO₃)–extractable P = 3.97 mg kg^?1, Mehlich III–extractable P = 6.13 mg kg^?1] with (+P = 60 mg P kg^?1 soil) or without P addition (0P). Phosphorus‐stress markedly reduced biomass accumulation and P uptake by roots and shoots. However, root–shoot ratio remained unaffected, implying that relative partitioning of biomass into roots and shoots had little role to play in shoot dry matter (SDM) production by cultivars. Biomass correlated significantly (P < 0.01) with total P uptake. Under P stress, the cultivars that produced greater root biomass were able to accumulate more total P content (r = 0.95^**), which in turn was related positively to SDM and total biomass (r > 0.89^**) and negatively to P‐stress factor (r = ?0.91^**). There was no correlation between P efficiency (PE) (relative shoot growth) and plant P, but PE showed a very significant correlation with shoot P content and SDM. Wide differences in growth and better performance of cultivars such as ‘Brown Raya’ and ‘Con‐1’ under P stress encouraged screening of more germplasm, especially in the field, to identify P‐tolerant cultivars.

In another study, potential relative agronomic effectiveness (RAE) of sparingly soluble P sources was investigated by growing two contrasting cultivars. The P sources incorporated into soil at 0, 10, 25, 50, and 100 mg P Kg^?1 were (i) powdered Jordan rock P (RP), (ii) triple superphosphate (TSP), (iii) powdered low‐grade TSP [TSP(PLG)], (iv) a mixture of RP + TSP compacted into pellets at 50:50 P ratio [RP + TSP(PelC)], and (v) a mixture of powdered RP + TSP at 50:50 P ratio [RP + TSP(PM)]. The RP was low in RAE and only 5 and 29% as effective as TSP in producing dry matter (DM) of P‐sensitive ‘B.S.A.’ and P‐tolerant ‘Brown Raya’ cultivars, respectively. There were no significant differences between TSP and RP + TSP(PelC) in DM yield of ‘Brown Raya,’ whereas, in the case of ‘B.S.A.’ RP + TSP(PM) was significantly less effective than RP + TSP(PelC) compared with TSP. Combined utilization of superior genome and P sources [such as TSP(PLG) and RP + TSP(PelC)] produced from low‐grade RP (that cannot be used either for direct application or acidulated P fertilizers) can be used as an alternative strategy for sustainable crop production, especially in resource‐poor environments. Further field trials at the level of cropping systems are needed.     

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.     

Differential Growth Performance of 15 Wheat Genotypes for Grain Yield and Phosphorus Uptake on a Low Phosphorus Soil Without and With Applied Phosphorus Fertilizer

ABSTRACT

Two field experiments were conducted to compare 15 wheat genotypes at two phosphorus (P) levels (zero-P control or low P level—without application of P fertilizer on soil with 8 mg extractable P kg^?1, and adequate P level—with P fertilizer applied at 52 kg P ha^?1) for yield, P uptake, and P utilization efficiency (P efficiency ratio—PER, P harvest index—PHI, and P physiological efficiency index—PPEI). On the average of two experiments, substantial and significant differences were observed among wheat genotypes for both grain and straw yields at both P levels. Grain yields ranged from 2636 to 4455 kg ha^?1 in the zero-P control, and from 2915 to 4753 kg ha^?1 at adequate P level. Genotype 5039 produced the maximum grain yield, while 6529-11 had the minimum grain yield at both P levels. Relative reduction in grain yield due to P deficiency stress (PSF) ranged from none to 32%, indicating differential P requirements of genotypes. Genotypes 4943, Pasban 90, Inqlab 91, PB 85, Lu 26s, 4770, Chakwal 86, 4072, 6544-6, and 5039 had little or no response to P application. Phosphorus responsive genotypes included FSD 83, Kohinoor 83, Parvaz-94, Pak 81, and 6529-11. A non-significant correlation (r = ?0.466, P > 0.05) between grain and PSF in zero-P control treatment also indicated the least effect of P deficiency on some wheat genotypes. A wide range of PPEI (270–380 kg grain kg^?1 P absorbed in grain + straw at control P level, and 210–330 kg grain kg^?1 P absorbed in grain + straw at adequate P level) indicated differential utilization of absorbed P by the genotypes for grain production. This indicated that wheat genotypes differed considerably in their P requirement for growth and responsiveness to P application. The findings also suggested that PPEI was a better parameter for measuring P efficiency than other parameters, and can be used for selecting P efficient genotypes, because it relates to the internal concentration of a nutrient and genetic makeup of plant. It is concluded that genotypes having ability to produce relatively high grain yield, good command to tune P within plant and high PPEI are suited to low P soil conditions. Genotypes 4072, Inqlab 91, 4943, Pak 81 and 5039 were P efficient and had above mentioned abilities, while genotypes FSD 83, 6544-6, and 6529-11 were P inefficient. It should be noted that traits related to P efficiency are inheritable and can be used to improve P use efficiency of a genotype through back cross breeding programs.     

Corn Responses to Phosphorus Application at Different Soil Phosphorus Levels on a Calcareous Soil

Phosphorus (P) in an high-pH soil may not be readily available to a crop, even though soil-testing procedures indicate high levels are present. A 2-year field study was conducted to determine corn yield responses to different rates of P fertilization as a function of soil-test P levels determined using the Mehlich-3 extractant. In 1 of the 2 years of this study, corn yields responded to P application across all soil P levels in a linear plateau fashion, indicating that P availability was limiting regardless of soil P levels. Where soil-test P was less than 40 mg kg^?1, corn yields showed a quadratic response to rate of P applied both years, and when soil-test P was between 40 and 60 mg kg^?1, corn yields showed a response only in the second year, when better growing conditions occurred. Soil-test P levels based on the Mehlich-3 extractant identified deficiencies in soil P availability to the crop, which could be corrected by P fertilization on a high-pH soil. Uptake efficiency of applied P was low, indicating that much of the P applied was not available to the crop.     

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.     

Phosphorus Use Efficiency of Common Bean Cultivars in Ethiopia

Phosphorus (P) deficiency in the soil is one of the major factors limiting common bean production in Ethiopia. A pot experiment was conducted in a glasshouse at Hawassa University in southern Ethiopia to evaluate twelve common bean cultivars for P use efficiency at three phosphorus rates (0, 120, and 240 kg P₂O₅ ha^?1). The results of the study revealed that the interaction effect of cultivar and P rates significantly (P < 0.01) influenced grain yield efficiency index (GYEI), grain yield and yield attributing traits, leaf P concentration, root length, diameter and surface area. Grain yield efficiency index at low and medium phosphorus rates indicated that Red-Wolaita, Dinkinesh, Tabour, Nasir and Haramaya are P-efficient, whereas Chore was found to be P-inefficient. These genotypic variations could be exploited for sustainable production of the crop by fitting suitable varieties to soils with variable P availability. Thus, the P-efficient cultivars indicated above could be recommended for cultivation by smallholder farmers in soil with low P availability that is dominant in the study area.     

Effects of limestone and phosphorus on nutrient availability and coastal bermudagrass yield on an ultisol

Abstract

This field study was conducted to evaluate nutrient availability and Coastal bermudagrass [Cynodon dactylon (L.) Pers.] yield response to factorial combinations of applied limestone and P in a strongly acid (pH 4.7), infertile soil. Limestone was applied at rates of 0, 672, and 3808 kg ha^‐1 to a Lilbert loamy fine sand (loamy, siliceous, thermic, arenic Plinthic Paleudult). Phosphorus was applied at rates of 0, 30, 60, 90, 120, 240, and 480 kg P ha^‐1. Soil pH in the surface 15 cm initially increased to 6.2 in response to the high limestone rate, but subsequently declined due to N fertilization. Lime increased soil test P, Ca, and Mg and decreased K and Al. The efficiency of increasing soil test P with fertilizer P was low, but improved as a consequence of liming. Coastal bermudagrass yield increased by as much as 37 percent from P application. Maximum yield coincided with 10 to 15 mg kg^‐1 or greater soil test P and tissue P concentrations that ranged from 1.6 to 2.2 g kg^‐1. Lime Increased tissue Ca and Mg, but had no effect on plant P concentrations. Yield was unaffected by lime despite its positive effect on soil P and an apparent K‐Mg antagonism. Plant nutrients obtained from deep rooting of the bermudagrass into an argiilic horizon may have precluded any positive effect of lime on Coastal bermudagrass yield.     

Yield,Yield Components,Soil Chemical Properties,Plant Physiology,and Phosphorus Use Efficiency in Soybean Genotypes

Expansion of soybean [Glycine max (L.) Merrill] cultivated in Brazil to regions with low fertility soils gave rise to studies on the possibility of obtaining highly productive cultivars with high nutrient use efficiency. An experiment in greenhouse conditions was conducted to assess phosphorus (P) use efficiency (PUE) by 13 soybean genotypes. The genotypes were grown in an Ustoxix Quartzipsamment with two P rates [0 (no P application) and 150 mg P kg^?1], whose source was monoammonium phosphate (MAP, P₂O₅ 44%). Shoot dry weight (SDW), grain yield (GY), grain harvest index (GHI), relative yield (RY), and physiological components (photosynthetic rate, stomatal conductance, respiratory rate, and internal CO₂ concentration) were influenced by soybean genotypes and P rates. Genotypes BMX Apolo RR, BRS 360RR, BRS 378RR, CD 219RR, DM 2302RR, TMG 7161RR, and Vtop RR were classified as non-efficient and non-responsive to P application, while BMX Potência RR, Vmax RR, FPS Solar RR, NA 5909RR, TMG 1066RR, and M 6210 IPRO were classified as efficient and responsive. Phosphorus application increased the values of physiological components, which was not observed for N, K, Ca, Mg, and S concentration in the leaves and grains. Soybean genotypes selection for increased P efficiency could help growers overcome the problem of soybean cultivation on new areas or degraded pastures.