Phosphorus Influx and Root‐Shoot Relations as Indicators of Phosphorus Efficiency of Different Crops

Abstract

The large variation in phosphorus acquisition efficiency of different crops provides opportunities for screening crop species that perform well on low phosphorus (P) soil. To explain the differences in P efficiency of winter maize (Zea mays L.), wheat (Triticum aestivum L.), and chickpea (Cicer arietinum L.), a green house pot experiment was conducted by using P‐deficient Typic ustochrept loamy sand soil (0.5 M NaHCO₃‐extractable P 4.9 mg kg^?1, pH 7.5, and organic carbon 2.7 g kg^?1) treated with 0, 30, and 60 mg P kg^?1 soil. Under P deficiency conditions, winter maize produced 76% of its maximum shoot dry weight (SDW) with 0.2% P in shoot, whereas chickpea and wheat produced about 30% of their maximum SDW with more than 0.25% P in shoot. Root length (RL) of winter maize, wheat, and chickpea were 83, 48, and 19% of their maximum RL, respectively. Considering relative shoot yield as a measure of efficiency, winter maize was more P efficient than wheat and chickpea. Winter maize had lower RL/SDW ratio than that of wheat, but it was more P efficient because it could maintain 2.2 times higher P influx even under P deficiency conditions. In addition, winter maize had low internal P requirement and 3.3 times higher shoot demand (i.e., higher amount of shoot produced per cm of root per second). Even though chickpea had 1.2 times higher P influx than winter maize, it was less P efficient because of few roots (i.e., less RL per unit SDW). Nutrient uptake model (NST 3.0) calculations satisfactorily predicted P influxes by all the three crops under sufficient P supply conditions (C_Li 48 µM), and the calculated values of P influx were 81–99% of the measured values. However, in no‐P treatment (C_Li 3.9 µM), under prediction of measured P influx indicated the importance of root exudates and/or mycorrhizae that increase P solubility in the rhizosphere. Sensitivity analysis showed that in low P soils, the initial soil solution P concentration (C_Li) was the most sensitive factor controlling P influx in all the three crops.     

Residual Effect of Phosphorus Fertilizer in a Low‐Humic Andosol with Low Extractable Phosphorus

Abstract

Phosphorus (P) fertilization is quite important for crop production grown on Andosols. Fertilizer P‐use efficiency was 17% in a long‐term wheat experiment on a low‐humic Andosol. Residual effects of P fertilization were investigated using field soils in pot experiments. Topsoil was collected from the plots with or without annual P fertilizer at the rate of 65 kg‐P ha^?1 for 23 years (nitrogen phosphorous potassium (NPK) soil and nitrogen potassium (NK) soil, respectively). There was no significant difference in dry matter of wheat and P uptake between NPK and NK soils. However, dry matter of rice and P uptake were higher in NPK soil than in NK soil. Inorganic aluminum P (Al‐P_i) and iron P (Fe‐P_i) increased in NPK soil. Increase in Al‐P_i and Fe‐P_i during 23 years contributed little to P uptake by wheat, and repeated P fertilization is indispensable to obtain acceptable grain yield.     

Transformation of Applied Phosphorus in a Calcareous Fluvisol

A new inorganic phosphorus (IP) fractionation scheme developed by Jiang and Gu was used in an incubation experiment to investigate the transformation of applied P in a calcareous fluvisol. The results show that after addition of common superphosphate (CSP), the Ca2-P in the soil decreased gradually and transformed largely to the less available Fe-P, Al-P and Ca8-P, rather than to the unavailable forms of Ca10-P and O-P. The different IP fractions ranked in the following order with respect to the increment by addition of CSP after 120 days of incubation: Fe-P> Al-P>Ca8-P>Ca2-P. After addition of pig manure, the content of Ca2-P in the soil increased rapidly at first and then decreased slowly, and the amount of different IP fractions accumulated after 120 days of incubation ranked in the following order: Ca2-P > Fe-P > Ca8-P > Al-P.     

Soil–Phosphorus Mobilization Potential of Phytate Mineralizing Fungi

Four most efficient phytase and phosphatase producing fungi belonging to genera Aspergillus, Trichoderma, and Penicillium were isolated from the rhizosphere soil of leguminous, cereal, and vegetable crops. Efficacy order of fungi in terms of phytate hydrolysis under laboratory conditions was Aspergillus > Penicillium > Trichoderma. The test fungi released more of extracellular (E) phytase than intracellular (I) phytase (E: I- 3.44 - 6.03:1) and produced acid phosphatase activity ranging from 367- 830 μmol pNP ml^?1 h^?1. Aspergillus niger possessed the twin ability of phosphate mineralization and solubilization. The incubation studies in compost-amended soil exhibited the higher competence of Penicillium chrysogenum to improve the soil available P and increase the level of extractable organic P under alkaline soil to benefit P nutrition. Developing microbial inoculant using P. chrysogenum strain and its subsequent application to soil may help the marginal farmer to replenish soil P more economically compared to chemical fertilizer.     

Influence of Organic Manure on Organic Phosphorus Fraction in Soils

The transformation of organic P(Po) from organic manures in two types of soils (ultisol and entisol) and the influences of external addition of organic substance or inorganic P(Pi) on Po under the condition of the 60% maximum water capacity were investigated.The results obtained from Po fractionation experiments indicated that all the Po fractions except for the highly resistant Po fraction decreased during incubation.Application of pig feces and cow feces could largely increase each fraction of Po in the soils.Immediately after application of organic manure into the soils a large part of labile and moderately labile Po from organic manure was transferred into moderately resistant Po,which might be due to the fact that Ca-or Mg-inositol P was precipitated into Fe-inositol P.However,the availability of Po from organic manure in the soils would increase again after incubation because of the transformation of moderately labile and resistant Po fractions into labile Po fractions.Addition of cellulose or Pi into the soils showed a good effect on increasing all the Po fractions except for the highly resistant Po,and this effect was much more pronounced when cellulose was applied in combination with Pi.Therefore,in view of the effect of organic manure on improving P nutrition to plant,attention should be paid to both the Po and the organic substances from organic manure,It is suggested that application of Pi fertilizer combined with organic manure may be referred to as an effective means of protecting Pi from chemical fixation in soil.     

Differences in Root Exudation Among Phosphorus‐Starved Genotypes of Maize and Green Gram and Its Relationship with Phosphorus Uptake

Abstract

Availability of phosphorus (P) in soil and its acquisition by plants is affected by the release of high and low molecular weight root exudates. A study was carried out to ascertain the qualitative and quantitative differences in root exudation among the genotypes of maize (Zea mays L.) and green gram (Vigna radiata L.) under P‐stress. Results showed that both inter‐ and intra‐species differences do exist among maize and green gram in terms of root exudation, P uptake, and shoot and root P content. In general, green gram, a legume crop, had greater root exudation compared to maize. However, the amino acid content of the total root exudates in maize was two‐fold as compared to green gram. The maize and green gram genotypes possessed genetic variability in root exudation. Irrespective of the species or genotypes, a positive relationship was found among P uptake rates, total root exudation, and shoot and root ³²P content. The amount of sugars and amino acid present in the root exudates of P‐starved seedlings also add to the variation in P uptake efficiency of genotypes.     

Effect of the Concentration of Phosphorus on Growth and Nutrition of Leucospermum cordifolium ‘Flame Spike’

The aim of this study was to determine how phosphorus (P) concentration affects growth, concentration and distribution of nutrients in Leucospermum cordifolium ‘Flame Spike’ (Proteaceae). The trials were performed at the School of Agriculture (ETSIA) of the University of La Laguna (28° 28′ 43′′ N, 16° 19′ 7′′ W) with 64 plants (1-year-old) grown for 12 months in silica sand, fed with nutrient solutions containing different levels of P_i (5, 10, 15 and 20 mg L^?1). At 6, 9, and 12 months, whole plants were taken from each experimental unit and divided into root, stem (main, first, second, and third growth) and leaves (adult, first, second, and third growth), which were measured, weighed, and analyzed. The data enabled a nutritional diagnosis, including the limiting P concentrations and nutrient interactions. P concentrations above 5 mg L^?1 caused a reduction in growth, which in the third samples was significant (P < 0.05). Plants treated with 15 and 20 mg L^?1 P attained similar dry weights (P > 0.05). Some young leaves showed a certain degree of chlorosis, probably due to iron (Fe) deficiency. Fully developed young leaves (YFEL) were suitable for nutritional diagnosis of P, and the P concentration of the nutrient solution affected the foliar manganese (Mn) concentration. This latter factor was related to the zinc (Zn) concentration in the roots.     

Phosphorus sorption by four soils receiving long‐term applications of fertilizer

Abstract

A laboratory study was conducted to evaluate P sorption in the Ap horizon of four soil series in the Ultisol order (Benndale Is, Hartsells fsl, Lucedale fsl, and Dewey sicl) receiving the same fertility treatments since 1929. Soil was collected in the spring of 1985 from 4 treatments: i) no‐lime, plus P (total fertilizer P = 1584 kg/ha from 1929 to 1985); ii) no‐K, plus P (total fertilizer P = 1584 kg/ha); iii) low‐P (total fertilizer P = 442 kg/ha); 4) standard treatment (total fertilizer P = 2376 kg/ha). The soils and treatments within a soil varied in pH, total P, Mehlich 1 extractable P, K, Ca and Mg, and KC1 extractable Al. The four soils had large differences in P sorption capacity which increased with increasing clay content. The Dewey (27 % clay) soil had the highest P sorption capacity and the Benndale (4 % clay) soil had the smallest P sorption capacity. Sorption of P within a soil was affected by the rate of added P and past fertility treatment. Treatment differences in P sorption were due primarily to the level of extractable P and soil pH. Within a given soil, P sorption (at a given rate of added P) generally decreased as the level of extractable P increased. Regression analysis of P sorption data for equilibrium P concentrations of 1 to 32 μmol/L showed that the parti‐ tioning between sorbed and solution P (buffer power) had not been changed by 56 years of annual applications of P. The maximum P sorption capacity of the four soils was decreased slightly by P fertilization.     

Effect of Submergence on Iron Transformation and Phosphorus Availability in Calcareous Soils

A thermostatic incubation experiment was carried out to estimate the effects of flooding periods,stalk application and P addition of Fe transformation and P availability in calcareous soils.Submergence increased amorphous Fe,especially in the case of stalk application.The newly formed amorphous Fe with a great surface area played an important role in Psorption;and submergence also stimulated the dissolution of inorganic P,thus increasing the availability of soil P in calcareous soils.Meanwhile,a part of soluble P was absorbed and fixed again on the surface of newly formed amorphous Fe,thus resulting in a decrease of P availability.Soil rapidly available P increased after 150-day incubation.There existed significantly negative correlations between soil amorphous Fe content and soil Fe-P and rapidly available P contents.Submerged conditions promoted the transformation of inorganic P added toward Fe-P in calcareous soils,especially in the case of stalk application.     

Increase of Available Phosphorus by Fly‐Ash Application in Paddy Soils

Abstract

Fly ash from the coal‐burning industry may be a potential inorganic soil amendment to increase rice productivity and to restore the soil nutrient balance in paddy soil. In this study, fly ash was applied at rates of 0, 40, 80, and 120 Mg ha^?1 in two paddy soils (silt loam in Yehari and loamy sand in Daegok). During rice cultivation, available phosphorus (P) increased significantly with fly ash application, as there was high content of P (786 mg kg^?1) in the applied fly ash. In addition, high content of silicon (Si) and high pH of fly ash contributed to increased available‐P content by ion competition between phosphate and silicate and by neutralization of soil acidity, respectively. With fly‐ash application, water‐soluble P (W‐P) content increased significantly together with increasing aluminum‐bound P (Al‐P) and calcium‐bound P (Ca‐P) fractions. By contrast, iron‐bound P (Fe‐P) decreased significantly because of reduction of iron under the flooded paddy soil during rice cultivation. The present experiment indicated that addition of fly ash had a positive benefit on increasing the P availability.     

Estimation of Phosphorus Status of Soil Fe‐Enriched Concretions with the Acid Ammonium Oxalate Method

Abstract

Iron (Fe)‐enriched concretions, a complex natural matrix with high chemical heterogeneity and phosphate‐sorption capacity, is widespread in soils with restrictive drainage in Greece. However, the phosphorus (P) status and related characteristics of Fe‐enriched concretions in agricultural soils in areas where P fertilization is mainly inorganic are relatively unknown. Active noncrystalline Fe and aluminum (Al) oxides (Feox, Alox), oxalate extractable P (Pox), P sorption capacity (PSC), and the degree of P saturation (DPS) of Fe‐enriched concretions from agricultural imperfectly drained soils in central Greece were determined using the acid ammonium oxalate method. The concretions contain 13 times as much Feox, twice as much Alox, and almost 15 times as much Pox than the surrounding soil matrix. Pox accounted for 50–80% of total P of the soil concretions, indicating strong accumulation of noncrystalline P components (Al‐ and Fe‐P). The PSC, expressed as a 0.5 (Alox+Feox), ranged from 184.7 to 314 mmol kg^?1, demonstrating the strong affinity of the Fe‐enriched concretions for P. The DPS, which represents the fraction of concretion sorbent surface coverage by P, was computed as 100 (Pox/PSC) with values ranging from 6 to 13% (mean=8%). The results of this study indicate that the Fe‐enriched concretions, due to their high noncrystalline Fe and Al oxides content, act as major sink of phosphate, controlling the location, mobility, and dynamics of P in agricultural soils with restrictive drainage.     

Dry‐Matter and Grain Yield,Nutrient Uptake,and Phosphorus Use‐Efficiency of Lowland Rice as Influenced by Phosphorus Fertilization

Abstract

Phosphorus (P) deficiency is one of the most yield‐limiting factors in lowland acid soils of Brazil. A field experiment was conducted during two consecutive years to determine dry‐matter and grain yield, nutrient uptake, and P‐use efficiency of lowland rice (Oryza sativa L.) grown on an acidic Inceptisol. Phosphorus rates used in the experiment were 0, 131, 262, 393, 524, and 655 kg P ha^?1 applied as broadcast through termophosphate yoorin. Dry‐matter yield of shoot and grain yield were significantly (P<0.01) and quadratically increased with P fertilization. Concentrations (content per unit dry‐weight leaves) of nitrogen (N), P, and magnesium (Mg) were significantly increased in a quadratic fashion with the increasing P rates. However, concentrations of potassium (K), calcium (Ca), zinc (Zn), copper (Cu), and iron (Fe) were not influenced significantly with P fertilization, and Mn concentration was significantly decreased with increasing P rates. Phosphorus use efficiencies (agronomic, physiological, agrophysiological, recovery, and utilization) were decreased with increasing P rates. However, magnitude of decrease varied from efficiency to efficiency.     

Phosphorus–Zinc Interactions in Two Barley Cultivars Differing in Phosphorus and Zinc Efficiencies

Abstract

Phosphorus (P)–zinc (Zn) interactions in two barley cultivars (Clipper and Sahara) differing in P and Zn efficiencies were investigated in a pot experiment carried out in a growth chamber. A highly calcareous field soil from a semi‐arid region of South Australia was used. Five levels of P addition and three levels of Zn addition were used. Plants were harvested five weeks after emergence. Increase in P supply significantly increased plant shoot biomass and tissue P concentrations in both cultivars, indicating that the soil used is P deficient. Zinc additions with low P additions caused slight decreases in plant biomass. However, Zn addition did increase plant growth when higher levels of P were applied demonstrating the importance of the balance Zn and P supply. Results showed that the genotypic difference between the two cultivars in P uptake efficiency (specific P uptake, SPU) can be altered by Zn–P interactions, and that total Zn uptake by Sahara was higher than Clipper irrespective of P supply. Tissue Zn concentrations decreased significantly with an increase in P supply in both cultivars. Increase in P supply drastically reduced the molar ratio of Zn to P in shoots (MRZP), and addition of Zn compensated for the reduction in MRZP due to P addition. The role of P–Zn interactions in the context of nutritional quality of plant food is also discussed.     

Fixation and Recovery of Added Phosphorus and Potassium in Different Soil Types of Pulse‐Growing Regions of India

Abstract

Fixation and recovery of added phosphorus (P) and potassium (K) were studied in different soil types of pulse‐growing regions. Amounts of P and K fixed increased in all the soils irrespective of type and texture. With the increase in levels of added P and K, maximum P fixation was observed at lower levels of added P (50 mg kg^?1). Alfisols showed maximum P‐fixation capacity (92.7%), followed by Vertisols (86.5%) and Inceptisols (76.6%) at 50 mg kg^?1 added P. However, K fixation increased with increasing levels of added K up to 200 mg kg^?1, and thereafter fixation either decreased or was maintained at similar levels. Vertisols showed higher K fixation than Inceptisols and Alfisols. Fertilizer P requirement per unit increase in available P in soil was highest in Bangalore (3.23) and lowest in Delhi (2.38). Fertilizer K requirement per unit increase in available K in soil was highest in Raipur and Gulbarga (1.75) and lowest in Ranchi (1.28).     

Phosphorus‐sorption characteristics of intensely weathered soils in south‐central kentucky

Abstract

Studies were conducted to investigate phosphorus (P)‐sorption characteristics of some intensely weathered soils in south‐central Kentucky. Phosphorus adsorption characteristics reflected the chemical and mineralogical properties of the soils studied. All adsorption data were adequately described by first order kinetic reactions which implied that the soils have uniform surfaces for P sorption. In spite of the limitations of the Langmuir equation, its usefulness in summarizing data into one adsorption maximum value was demonstrated by nearly identical adsorption maxima estimated by three linear transformations of the equation and small deviations from the observed maxima. Variations in adsorption maxima between surface and subsoils and among soils were best correlated with extractable aluminum (Al) (r = 0.93, p<0.01) and crystalline iron (Fe) oxy‐hydroxides (r = 0.97, p<0.01). Clay content was also highly correlated with P sorption (r = 0.97, p <0.01) as well as with extractable Al (r = 0.83, p<0.05) and crystalline Fe oxides (r = 0.92, p<0.01) suggesting that its contribution may have been through its association with these soil components. In contrast, organic matter had a negative association with P sorption (r = ‐0.83, p<0.05). The results indicate higher P sorption in subsoil than in surface horizons, controlled mainly by extractable Al and crystalline Fe oxyhydroxides.     

Phosphorus Mobility Through Soil Increased with Organic Acid-Bonded Phosphorus Fertilizer (Carbond® P)

Phosphorus fertilizer is critical to crop production but inefficiently absorbed and consequently linked to surface water pollution. Phosphorus mobility was measured on three soils using 0.18 m soil columns treated with Carbond® P (CBP, 7-24-0), ammonium polyphosphate (APP, 10-34-0) and monoammonium phosphate (MAP, 11-52-0) applied either by mixing thoroughly or in concentrated bands at rates of 20 and 30 kg P ha^?1. Mobility of P was measured in leachate collected 24, 48, 110 and 365 d after fertilization (daf). Carbond® P produced the highest total P leachate values over 365 d study period compared to MAP or APP for both mixed and band applications. On individual days, CBP generally allowed more soluble P leachate than MAP or APP up until 110 daf (one exception) but not at 365 daf. Higher solubility of P with CBP explains higher P uptake by plants from soils and could reduce total P applications to crops.     

Determination of Optimum Rate and Growth Stage for Foliar‐Applied Phosphorus in Corn

Abstract

Foliar applications of fertilizer phosphorus (P) could improve use efficiency by minimizing soil applications. Nine experiments were conducted in 2002 and 2003 to determine foliar P rates and appropriate growth stages for application. Treatments comprised of 10 factorial combinations of three foliar P application timings and four rates of foliar P. Foliar application times were V4 (collar of fourth leaf visible), V8 (collar of eighth leaf visible), and VT (last branch of the tassel completely visible but silks not yet emerged) corn growth stages. Foliar P rates were 0, 2, 4, and 8 kg ha^?1. Foliar P applied at the VT growth stage improved grain and forage P concentration, which was reflected in increased grain yield in some of the experiments. A foliar P rate of 8 kg ha^?1 improved yield to some extent and forage and grain P concentration more than the smaller rates. The results suggest that foliar P could be used as an efficient P‐management tool in corn when applied at the appropriate growth stage and rate.     

Release of Inorganic Phosphorus from Soils by Low‐Molecular‐Weight Organic Acids

Abstract

Low‐molecular‐weight (LMW) organic acids are found in soils. They originate from the activities of various microorganisms in soils or may be exuded from the roots of living plants. Several of those organic acids are capable of forming stable organo‐metal complexes with various metal ions found in soil solutions. As a result, these processes may lead to the release of inorganic phosphorus (P) associated with aluminum (Al), iron (Fe), and calcium (Ca) in soil minerals. The release of P from soils by LMW organic acids may be important to the P nutrition of plants. Studies on the release of P from soils by a variety of LMW organic acids showed that, in general, the di‐ and tricarboxylic acids were the most effective in releasing P from two Iowa soils, whereas the monocarboxylic, phenolic, and mineral acids released similar amounts of P. Oxalic, malonic, citric, and, in some cases, malic and tartaric acids were the most effective in releasing inorganic P from the two surface soils studied. There was an inverse relationship between the amounts of P released from soils and the pK_a values of the organic acids. The amounts of P released from soils were significantly correlated with the published stability constants for the formation of organic complexes of Al, Fe, or Ca (log K_Al, log K_Fe, or log K_Ca values). In general, the aliphatic acids containing α‐caboxyl and β‐hydroxyl functional groups or phenolic acids containing ortho‐hydroxyl groups were more effective in causing the release of P from soils than similar organic acids having other functional group combinations.     

Phosphorus–microbes interaction on growth,yield and phosphorus-use efficiency of irrigated cotton

The phosphorus-use efficiency of crops in high pH soil is low. A randomized complete block design in a 3 × 2 split-plot experiment was conducted on a high pH silt loam (Typic Ustochrepts) to evaluate whether P-solubilizing microbial (PSM) inocula were able to improve the P fertilization effects on irrigated cotton (Gossypium hirsutum L., cultivar CIM-482). Cotton was planted after seed treatment with PSM inoculation at 0, 22 and 44 kg P ha^?1. Results showed that soil microbial populations were significantly higher throughout the cotton-growing season in response to P fertilization and PSM inoculation. Both P fertilization and PSM inocula exerted a significant effect on cotton biomass and Puptake without an interaction. Economic analyses suggest that PSM inocula alone significantly increased P-use efficiency (8%), reduced cost and improved net income (by $36 ha^?1) of irrigated cotton production. Moreover, the relationship between relative yield and P fertilization with PSM inocula showed that 95% of the maximum yield of cotton was produced at 22 kg P ha^?1, whereas in the absence of PSM inocula, 95% relative yield was obtained at 36 kg P ha^?1, asaving of ～39% applied P with PSM inoculation.