Kinetics of phosphorus and potassium release from rock phosphate and waste mica enriched compost and their effect on yield and nutrient uptake by wheat (Triticum aestivum)

An attempt was made to study the efficient use of rice straw and indigenous source of phosphorus and potassium in crop production through composting technology. Various enriched composts were prepared using rice straw, rock phosphate (RP), waste mica and bioinoculant (Aspergillus awamori) and kinetics of release of phosphorus and potassium from enriched composts and their effect on yield and nutrient uptake by wheat (Triticum aestivum) were carried out. Results showed sharp increases in release in water-soluble P and K from all the composts at 8th to 12th day of leaching, thereafter, it decreased gradually. Maximum release of water-soluble P and K were obtained in ordinary compost than enriched composts during the initial stages of leaching, but their differences narrowed down at latter stages. Data in pot experiments revealed that enriched composts performed poorly than diammonium phosphate during initial stages of crop growth, but they out yielded at the latter stages, particularly at maturity stage, as evident from their higher yield, uptake, nutrient recoveries and fertility status of P and K in soils. Moreover, enriched composts prepared with RP and waste mica along with A. awamori resulted in significantly higher biomass yield, uptake and recoveries of P and K as well as available P and K in soils than composts prepared without inoculant. Results indicated that enriched compost could be an alternate technology for the efficient management of rice straw, low-grade RP and waste mica in crop production, which could help to reduce the reliance on costly chemical fertilizers.     

Improving rock phosphate availability through feeding, mixing and processing with composting manure

The objective of this study was to improve the availability of phosphorus (P) from rock phosphate (RP) through feeding, mixing and composting manure. The experiment was conducted as a 3 x 2 split-plot design. Manure was collected from 12 Boran steers (200+/-4.5 kg live weight) fed a basal diet of Napier grass (Pennisetum purpureum) at 2.5% body weight on a dry matter (DM) basis. The main plot treatments were (i) manure from steers supplemented with 113 g Busumbu rock phosphate (BRP) per day (FBRP), (ii) manure from steers not supplemented with BRP, feces mixed with 113 g BRP per day (MBRP) and (iii) manure from steers not supplemented with BRP and feces not mixed with BRP (CONT). The sub-plots comprised composting the manure either (i) mixed with 440 g of wheat (Triticum aestivum L.) straw per kg fresh feces (WS) or (ii) without straw (WOS). The manure was composted in 200 L plastic bins for 90 days. After 90 days, P availability was evaluated (i) by aerobic laboratory incubation at 25 degrees C for 1, 2, 4, 8, 12, and 16 weeks and (ii) by greenhouse agronomic evaluation study using maize (Zea Mays L.) as the test crop in either a humic Nitosol or an Andosol. In the laboratory incubation study, resin P was higher (p<0.05) for the WS compost than for the WOS compost; values were higher (p<0.05) for the Andosol than for Nitosol and followed the order of FBRP-WS, Andosol>FBRP-WS, Nitosol>MBRP-WS, Andosol>MBRP-WS, Nitosol>FBRP-WOS, Andosol>FBRP-WOS, Nitosol. In the greenhouse evaluation, maize crops in the WS compost had higher (p<0.05) biomass yield than the reference fertilizer, triple super phosphate, (173% versus 196%; Andosol and Nitosol, respectively). The biomass yield and P uptake relative agronomic effectiveness (RAE) for WS compost was also higher (p<0.05) than that of WOS compost (184 versus 3+/-0.8 and 242 versus 162+/-0.2, WS and WOS, biomass yield and P uptake, respectively). Nitosol biomass yield and P uptake RAE were also higher (p<0.05) than for the Andosol (99 versus 88+/-0.8 and 332 versus 72+/-0.2, Nitosol and Andosol, biomass yield and P uptake, respectively). The results show that P-enriched composting in the presence of wheat straw significantly increased P availability and increased plant growth. However, in terms of plant growth, there was no additional benefit of first feeding the RP to steers before composting the manure because most of the RP fed seem to have been utilized by the animal.     

Effects of root-dip treatment with certain phosphate solubilizing microorganisms on the fusarial wilt of tomato

Root-dip application of Bacillus subtilis, Pseudomonas fluorescens, Aspergillus awamori, Aspergillus niger and Penicillium digitatum resulted in significant decline in the rhizosphere population of Fusarium oxysporum f. sp. lycopersici. A significant decrease in the severity of wilt occurred with A. awamori (37.1%) and P. digitatum (21.3%) compared to the control. Root-dip treatment with the phosphate solubilizing microorganisms tested resulted in significant increase in the yield of tomato, being greatest with A. awamori and P. digitatum in pathogen inoculated (36% and 33%) and uninoculated plants (19% and 23%). A chemical fungicide gave 24% better yield.     

Effect of VAM inoculum carry-over on the successive cropping of maize and mungbean

A field study to determine the endomycorrhizal inoculum carry-over effect of the first crop [maize inoculated with Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe] on the succeeding crop (mungbean) was carried out in fumigated and nonfumigated acidic soil (pH 5.3) with moderate extractable P (Olsen 23 ppm). G. mosseae inoculation increased maize dry matter and grain yield over the uninoculated control in the nonfumigated soil. The maize inoculation failed to carry the effective inoculum over to the mungbean crop planted immediately after maize harvest and thus did not increase root colonization and grain yield of the succeeding crop. Fresh inoculation of the mungbean with G. mosseae increased grain yield over the uninoculated control.     

Effect of fungal consortium and animal manure amendments on phosphorus fractions of paddy-straw compost

The study was conducted to reveal the type of phosphorus (P) fractions present in mature compost prepared by co-composting paddy straw (P.S) with cattle manure (CM), farm yard manure (FYM) and poultry manure (PM), each added separately as nitrogen (N) and P source. A consortium of phytate mineralizing fungi developed by including Aspergillus niger ITCC 6719, Aspergillus flavus ITCC 6720 and Trichoderma harzianum ITCC 6721 was applied for recovery of P from plant and animal residues. Chemical evaluation of compost after 4 months of aerobic decomposition revealed that inoculation improved the sodium bicarbonate-extractable P content of CM and FYM supplemented P.S compost by 32.3% and 23.5% respectively compared with their respective un-inoculated control. However, the peak values for water soluble-P fractions were recorded in CM–straw compost followed by PM–straw compost. Fungal inoculation also improved the agronomic quality of PM–straw compost as the latter had the highest total P content and lowest C:N and E4/E6 ratio of 18:1 and 5.36:1 respectively. The recovery of organic P from agricultural residue has the potential to reduce the application of synthetic P fertilizer. P-enriched organic manure can offer potential environment and economic benefits to farmers under sustainable agriculture.     

Interaction of phosphorus fertilizer form and soil medium on Douglas-fir seedling phosphorus content,growth and photosynthesis

Douglas-fir seedlings were grown in containers in peat-vermiculite or mineral soil each amended with different levels of concentrated superphosphate (CSP) or a granulated North Carolina phosphate rock (RP). Media dilute acid-fluoride extractable phosphorus (DAP), seedling photosynthesis, weights, and tissue P concentrations were measured at 65±3 and 105±3 days. DAP was highly correlated with soluble fertilizer P (but not total P) added at the beginning of the experiment. Considerable soluble P was lost from peat-vermiculite but not from the mineral soil. Seedling total P content was proportional to the amount of soluble P per container at both harvests, but was greater for a given level of soluble P in the organicversus the mineral medium. Added soluble P increased foliar P concentrations, plant P content, and dry weight. Net carbon uptake was highly correlated with added levels of soluble P, foliar P concentrations, and with total P content. The internal efficiency of P from the RP source was less than P from CSP with respect to P contentversus growth, net CO₂ uptake, and net photosynthesis rates. At the end of the experiment, seedling P content plus DAP remaining in the media for the higher fertilizer rates accounted for 75% of the originally added soluble P in the mineral soils, but only 15% of the originally added soluble P in the organic media.     

Phytoremediation of arsenic contaminated soil by Pteris vittata L. II. Effect on arsenic uptake and rice yield

A greenhouse experiment evaluated the effect of phytoextraction of arsenic from a contaminated soil by Chinese Brake Fern (Pteris vittata L.) and its subsequent effects on growth and uptake of arsenic by rice (Oryza sativa L.) crop. Pteris vittata was grown for one or two growing cycles of four months each with two phosphate sources, using single super phosphate (SSP) and di-ammonium phosphate (DAP). Rice was grown on phytoextracted soils followed by measurements of biomass yield (grain, straw, and root), arsenic concentration and, uptake by individual plant parts. The biomass yield (grain, straw and rice) of rice was highest in soil phytoextracted with Pteris vittata grown for two cycles and fertilized with diammonium phosphate (DAP). Total arsenic uptake in contaminated soil ranged from 8.2 to 16.9 mg pot(-1) in first growing cycle and 5.5 to 12.0 mg pot(-1) in second growing cycle of Pteris vittata. There was thus a mean reduction of 52% in arsenic content of rice grain after two growing cycle of Pteris vittata and 29% after the one growing cycle. The phytoextraction of arsenic contaminated soil by Pteris vittata was beneficial for growing rice resulted in decreased arsenic content in rice grain of <1 ppm. There was a mean improvement in rice grain yield 14% after two growing cycle and 8% after the one growing cycle of brake fern.     

Effects of inoculation of phosphate-solubilizing microorganisms and an arbuscular mycorrhizal fungus on mungbean grown under natural soil conditions

 The effect of inoculation of the phosphate-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the arbuscular mycorrhizal (AM) fungus Glomus fasciculatum with or without Mussoorie rockphosphate (MRP) was studied in a P-deficient natural non-disinfected sandy soil on mungbean (Vigna radiata). The AM levels increased following the addition of MRP or inoculation with PSM or G. fasciculatum. Both grain and straw yield of mungbean increased following inoculation with PSM or the AM fungus. In general, the increase in yield was higher in the presence of MRP and inoculation with a combination of PSM and AM fungus. Highest N and P uptake by mungbean was recorded after treatment with a combination of B. circulans, C. herbarum and G. fasciculatum in the presence of MRP. Generally the PSM population increased after AM fungus inoculation. Accepted: 13 October 1997     

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.     

Effects of various straw incorporation strategies on soil phosphorus fractions and transformations

Returning straw to the field is an effective method for optimizing the soil phosphorus (P) availability, in which bacteria play an important role. However, the effects of various straw incorporation strategies on P transformation between different soil P pools remain unclear. In this study, variations in soil P fractions, phosphatase activities and the abundance of phosphatase genes (phoD, phoX and phoC) as well as a P-solubilizing gene (pqqC) at DNA (total) and cDNA (transcribed) levels were analysed in three straw incorporation treatments, including chopped straw (StrawD), straw compost (Compost) and straw-derived biochar (Biochar), and control (no straw, CK). Compared with the CK, the moderately labile inorganic P (NaOH I-P_i) content significantly decreased and the non-available P (Residual P) content significantly increased in the StrawD treatment. At the same time, phosphodiesterase (PD) activity and the transcribed phoC and phoX genes as well as total pqqC gene abundance significantly increased in the StrawD treatment, suggesting that the input of chopped straw stimulated P transformations from both organic and inorganic P pools. In addition, the stable P_i (NaOH II-P_i) content and total pqqC gene abundance in the Biochar treatment were significantly higher than that in the CK, indicating that the input of biochar increased the NaOH II-P_i that could release available P by Pi-solubilizing bacteria. In comparison to the CK, the Compost input significantly decreased one labile Pi (resin-P_i) only. However, its P fractions were significantly different from that of CK, Biochar and StrawD treatments, suggesting that the effects of compost input on P should not be ignored. In conclusion, chopped straw input increased soil P transformation but not available P, biochar input may promote inorganic P transformation, and compost input has a latent effect on P transformation. The study provided a comprehensive understanding of straw incorporation strategies for regulating soil P availability.     

Responses of Wheat Yield,Macro- and Micro-Nutrients,and Heavy Metals in Soil and Wheat following the Application of Manure Compost on the North China Plain

The recycling of livestock manure in cropping systems is considered to enhance soil fertility and crop productivity. However, there have been no systematic long-term studies of the effects of manure application on soil and crop macro- and micro-nutrients, heavy metals, and crop yields in China, despite their great importance for sustainable crop production and food safety. Thus, we conducted field experiments in a typical cereal crop production area of the North China Plain to investigate the effects of compost manure application rates on wheat yield, as well as on the macro-/micro-nutrients and heavy metals contents of soil and wheat. We found that compost application increased the soil total N and the available K, Fe, Zn, and Mn concentrations, whereas the available P in soil was not affected, and the available Cu decreased. In general, compost application had no significant effects on the grain yield, biomass, and harvest index of winter wheat. However, during 2012 and 2013, the N concentration decreased by 9% and 18% in straw, and by 16% and 12% in grain, respectively. With compost application, the straw P concentration only increased in 2012 but the grain P generally increased, while the straw K concentration tended to decrease and the grain K concentration increased in 2013. Compost application generally increased the Fe and Zn concentrations in straw and grain, whereas the Cu and Mn concentrations decreased significantly compared with the control. The heavy metal concentrations increased at some compost application rates, but they were still within the safe range. The balances of the macro-and micro-nutrients indicated that the removal of nutrients by wheat was compensated for by the addition of compost, whereas the level of N decreased without the application of compost. The daily intake levels of micronutrients via the consumption of wheat grain were still lower than the recommended levels when sheep manure compost was applied, except for that of Mn.     

栽培模式对旱地小麦产量和籽粒养分含量的影响

通过田间试验,研究地膜覆盖、秸秆还田和种植绿肥对冬小麦籽粒产量和籽粒养分含量的影响.结果表明:与传统模式相比,地膜覆盖并不总能提高旱地小麦产量,3年平均产量无显著变化,但籽粒磷吸收量却增加8.4%,磷含量平均提高13.0%;籽粒氮、硫和铁吸收量分别降低12.6%、15.0%和11.1%,含量分别降低12.1%、12.9%和10.1%,锌含量无显著变化.秸秆还田使小麦籽粒产量下降12.1%,籽粒氮、硫和铁吸收量分别降低22.5%、21.0%和19.8%,含量分别降低10.1%、9.4%和3.8%;磷吸收量降低9.8%,含量却增加5.0%,锌含量亦无显著变化.种植绿肥的小麦籽粒产量降低12.1%,籽粒氮和锌吸收量无显著变化,含量分别增加12.1%和12.6%,对磷、硫和铁含量无显著影响.可见,旱地条件下,不同栽培模式引起的籽粒产量增减与其养分吸收量变化不一致是养分含量变化的主要原因.在旱地小麦生产中,需注意地膜覆盖和秸秆还田的减产风险及对籽粒养分的不利影响,适当调控氮肥用量,保证小麦产量形成的养分需求,协调氮、硫、铁养分的吸收利用.种植绿肥能培肥土壤,提高籽粒氮和锌含量,但也应注意其减产问题.     

Enzymatic removal of alkaline phosphatase from renal brush-border membranes. Effect on phosphate transport and on phosphate binding

Brush-border membrane vesicles prepared from rabbit kidney cortex were incubated at 37 degrees C for 30 min with phosphatidylinositol-specific phospholipase C. This maneuver resulted in a release of approx. 85% of the brush-border membrane-linked enzyme alkaline phosphatase as determined by its enzymatic activity. Transport of inorganic [32P]phosphate (100 microM) by the PI-specific phospholipase C-treated brush-border membrane vesicles was measured at 20-22 degrees C in the presence of an inwardly directed 100 mM Na+ gradient. Neither initial uptake rates, as estimated from 10-s uptake values (103.5 +/- 6.8%, n = 7 experiments), nor equilibrium uptake values, measured after 2 h (102 +/- 3.4%) were different from controls (100%). Control and PI-specific phospholipase C-treated brush-border membrane vesicles were extracted with chloroform/methanol to obtain a proteolipid fraction which has been shown to bind Pi with high affinity and specificity (Kessler, R.J., Vaughn, D.A. and Fanestil, D.D. (1982) J. Biol. Chem. 257, 14311-14317). Phosphate binding (at 10 microM Pi) by the extracted proteolipid was measured. No significant difference in binding was observed between the two types of preparations: 31.0 +/- 9.37 in controls and 29.8 +/- 8.3 nmol/mg protein in the proteolipid extracted from PI-specific phospholipase C-treated brush-border membrane vesicles. It appears therefore that alkaline phosphatase activity is essential neither for Pi transport by brush-border membrane vesicles nor for Pi binding by proteolipid extracted from brush-border membrane. These results dissociate alkaline phosphatase activity, but not brush-border membrane vesicle transport of phosphate, from phosphate binding by proteolipid.     

Effect of acidulation of high cadmium containing phosphate rocks on cadmium uptake by upland rice

Little information is available in literature on Cd uptake by crops from either phosphate rock (PR) or partially acidulated PR (PAPR). The purpose of this greenhouse experiment was to study the effect of acidulation of two PRs having high Cd content (highly reactive North Carolina PR and low-reactive Togo PR) on Cd uptake by upland rice. The degrees of acidulation with H₂SO₄ were 100% for North Carolina PR (NC-single superphosphate [SSP]) and 50% or 100% for Togo-PR (i.e., Togo PAPR or Togo-SSP). Separation of the confounding effect between P uptake and Cd uptake from various P sources was made by adding 200 mg P/kg as KH₂PO₄ to all the treatments. Rates of Cd added from various P sources were 50–400 µg Cd/kg. Upland rice (Oryza sativa L.) was grown on two acid soils (Hartsells, pH 5.0 and Waverly, pH 5.6) to maturity.The results show that Cd uptake by rice grains followed the order of NC-SSP> NC-PR and Togo SSP> Togo PAPR> Togo PR. The results also showed that most of the Cd uptake was retained in rice roots and straw. Total uptake of Cd, Ca, and P by rice plant (root, straw, and grain) was higher from NC-PR than from Togo-PR. Cd concentration in rice grains showed no significant difference between NC-PR and Togo-PR, whereas Cd concentrations in root and straw were higher with NC-PR than that with Togo-PR. There was a significant relationship between total Cd uptake by rice plant and Cd extracted by DTPA from soils treated with various P sources at 400 µg Cd/kg.     

Phosphorus availability to maize as influenced by organic manures and fertilizer P associated phosphatase activity in soils

Laboratory incubation and green house studies were conducted to compare the P availability of organic manures and P uptake from organic manures by maize. Various organic manures viz. Poultry manure (PM), Farmyard manure (FYM), Green manure (GM) and Crop residue (CR) and graded levels of fertilizer P were applied in Samana sandy loam and Ladhowal silt loam soils and incubated for 7, 15, 30, 60 and 90 days. Samples were analyzed for P availability, P uptake and alkaline phosphatase activity. The overall, phosphatase activity, Paranitrophenyl phosphate (PNP h⁻¹ g⁻¹), in the Ladhowal silt loam soil was higher than in the Samana sandy loam soil. As the level of inorganic P increased, the release of PNP h⁻¹ g⁻¹ soil also increased. Among different organic manures, PM registered the highest enzyme activity followed by FYM, GM and CR. Compared to 7 days incubation a slightly higher increase in PNP was noticed in samples from 90 days incubation in both soils. The differential phosphatase activity in the organic manures was further reflected in dynamic P availability. The highest amount of Olsen extractable P was in PM-treated soil followed by FYM, GM and field pea crop residue. Organic manure addition along with inorganic P, irrespective of the source, increased the Olsen extractable P throughout the incubation period. Total P uptake by maize increased with the increasing level of inorganic P in both soils. The highest uptake was obtained in PM-treated soil and lowest in the CR-amended soil. We conclude that PM more readily supplies P to plants than other organic manure sources.     

不同有机物料对渭北旱塬耕地土壤短期培肥效应的综合评价

通过田间试验和室内分析,研究了施用不同有机物料对渭北旱塬耕地土壤化学性质和酶活性的影响,选取有机质等10个能够反映土壤肥力质量特性的定量因子作为评价指标,采用因子分析对土壤肥力质量进行综合评分,然后用欧氏距离最短距离法对其进行聚类,最后利用作物产量结果进行验证.结果表明：通过土壤有机培肥,土壤肥力质量和作物产量均有显著提高,与单施化肥相比,施加秸秆堆肥和厩肥处理的小麦产量分别提高了20.43%和22.38%;对土壤肥力综合进行评价,秸秆堆肥配施化肥的土壤肥力质量最高,综合得分达56.53,厩肥配施化肥较高,高量秸秆配施化肥次之.可见,通过秸秆堆肥或厩肥配施化肥进行培肥土壤,能显著提高土壤肥力水平,从而提高作物产量;利用有机质等10项土壤肥力特性因子,采用因子分析对土壤肥力质量进行综合评价,能够准确反映土壤肥力水平,预测土壤生产力状况.     

Effect of Tilemsi phosphate rock-solubilizing microorganisms on phosphorus uptake and yield of field-grown wheat (Triticum aestivum L.) in Mali

With the broad aim of biologically improving P uptake by wheat fertilized with Tilemsi phosphate rock (TPR), we investigated the effect of inoculation with TPR-solubilizing microorganisms isolated from Malian soils and with a commercial isolate of the arbuscular mycorrhizal (AM) fungus Glomus intraradices (Gi). AM root length colonization, and growth yield and P concentration of the cultivar Tetra of wheat were measured under field conditions in Mali. Experimental plots were established in Koygour (Diré) during the 2001–2002 cropping season. Inoculation treatments included two fungal isolates, Aspergillus awamori (C1) and Penicillium chrysogenum (C13), and an isolate of Pseudomonas sp. (BR2), used alone or in fungus-bacterium combinations in the presence or absence of the AM fungus Gi. In fertilized treatments, 0 or 30 kg P ha⁻¹ was applied as TPR or diammonium phosphate (DAP). In 45-day-old wheat plants, the highest root length AM colonization (62%) was observed with TPR fertilized wheat inoculated with Gi and BR2. Our results suggest that BR2 is a mycorrhizal-helper bacteria and a good plant growth-promoting rhizobacteria. In fact, inoculation of wheat Tetra fertilized with TPR with a combination of Gi, BR2 and C1 produced the best grain yield with the highest P concentration. This work shows that by inoculating seeds with TPR-solubilizing microorganisms and AM fungi under field conditions in Mali it is possible to obtain wheat grain yields comparable to those produced by using the expensive DAP fertilizer.     

磷肥施用方式及类型对冬小麦产量和磷素吸收的影响

采用田间微区试验研究不同磷肥施用方式和种类对冬小麦生长和当季磷素吸收的影响.磷肥种类为磷酸二氢钙(MCP)和磷酸氢二铵(DAP),施用方式包括表面撒施,种子正下方5 cm条施,种子下方5 cm、偏3 cm条施,种子下方5 cm、偏10 cm条施,种子正下方20%土体混施5种.结果表明: 种子正下方5 cm条施对小麦的增产效果最高,其中磷酸二氢钙的产量达到7.63 t·hm^-2,磷酸氢二铵的产量达到7.99 t·hm^-2,分别较农民习惯撒施方式增产10.3%和10.7%.在5种施磷方式中,偏10 cm条施的小麦产量最低(6.60～6.77 t·hm^-2).种子正下方5 cm条施和20%土体混施处理的小麦总吸磷量均处于较高水平(34.4～35.6 kg·hm^-2),偏10 cm条施在小麦各生长阶段的吸磷量均显著低于其他施磷方式,但磷酸氢二铵偏10 cm条施的小麦总吸磷量较磷酸二氢钙高11.9%.表明将磷肥近距离集中施用于种子附近为该地区较为合理的施磷方式,在偏远距离条施下磷酸氢二铵对小麦的磷素吸收利用效果优于磷酸二氢钙.     

The effect of phosphorus deficiency on nutrient uptake,nitrogen fixation and photosynthetic rate in mashbean,mungbean and soybean

Phosphorous (P) fertilization is the major mineral nutrient yield determinant among legume crops. However, legume crops vary widely in the ability to take up and use P during deficiency. The aim here was to compare P uptake and translocation, biological nitrogen fixing ability and photosynthetic rate among mashbean (Vigna aconitifolia cv. ‘Mash-88’), mungbean (Vigna radiata cv. ‘Moong-6601’) and soybean (Glycine max L. cv. ‘Tamahomare’) during deficiency in hydroponics. Two treatments, the withdrawal of P from the solution (P-deprivation) and continued P at 160 μM (P sufficient) were effected at the pod initiation stage. Plants were grown for 20 days. Short-term labeling with ³²P showed the uptake and distribution of P into plant parts. Withdrawal of P from the solution reduced biomass, photosynthetic activity, and nitrogen fixing ability in mungbean, and mashbean more than in soybean. P deprivation decreased P accumulation more than N accumulation. The decrease was more severe in mungbean and mashbean than soybean. More P was translocated and distributed into leaves in soybean than in mungbean and mashbean. Leaf P amount was more correlated to leaf area than to photosynthetic rate per unit leaf area among all three legume species. The results indicate that selection for increased efficiency of P utilization and leaf area may be used to improve leguminous crops.     

Different performances of soil phosphate tests for reflecting the effects of buffering capacity on uptake of native phosphate with time

The ability of two sodium bicarbonate (Colwell and Olsen) and two ammonium fluoride (Bray I and Bray II) soil tests to reflect the effect of phosphate buffering capacity of the soil on plant growth through time was studied on ten Argentine soils. The soils were divided into three groups (low, medium and high buffering capacity) according to a buffering index calculated from the slope of the Freundlich equation. The relation between phosphate extracted by soil tests and both relative yield and phosphate uptake of rye grass plants was affected by the phosphate buffering capacity of the soil. The effect of buffering on that relation was more marked for the sodium bicarbonate tests (specially Colwell) than for the Bray tests. This effect was consistent with time. Hence, adjustment for buffering would be more important for the sodium bicarbonate tests than for the Bray tests. Soils with high buffering capacity were able to sustain a greater rate of phosphate uptake. The effect of buffering on the relation between soil tests and both relative yield and phosphate uptake was greatest when the plants were young and decreased with time. This effect would therefore be very important for the early nutrition of annual pasture or crop species.