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1.
Six phosphorus (P) fertilizers recycled from sewage sludge [Struvite SSL, Struvite AirPrex®, P‐RoC®, Mephrec®, Pyrolysis coal and Ash (Mg‐SSA)] were tested for their plant availability in potted soil of pH 7.2 under greenhouse conditions. The crop sequence simulated a rotation of red clover (Trifolium pratense L.), maize (Zea maize L.), and ryegrass (Lolium perenne L.). Other P fertilizer treatments included: Phosphate Rock (PR), Calcium dihydrogen phosphate [Ca(H2PO4)2], and an unfertilized control. Additionally, soil was regularly inoculated with two strains of plant growth‐promoting rhizobacteria (PGPR; Pseudomonas sp. Proradix, and Bacillus amyloliquefaciens) to test their ability to increase P availability to plants. Sequential P fractionation was conducted to link the amount of readily available P in fertilizers to plant P acquisition. Shoot P content and dry matter of maize decreased in the following order: Struvite SSL ≥ Ca(H2PO4)2 > P‐RoC® ≥ Struvite AirPrex® ≥ Mephrec® > Pyrolysis coal ≥ Mg‐SSA ≥ PR ≥ unfertilized. Rhizobacteria did not affect shoot biomass or P content. The results show that red clover might have mobilized substantial amounts of P. Sequential P fractionation was not suitable to predict the efficacy of the fertilizers. Generally, the sewage sludge‐based fertilizers tested proved to be suitable alternative P sources relevant to organic farming systems. However, the efficacy of recycled fertilizers is strongly dependent on their specific production conditions.  相似文献   

2.
Most soils in Nigeria are known to be slightly acidic and very low in plant‐available P. These soils need to be fertilized for optimal crop production but cost and scarcity of mineral P fertilizers shifted attention to making direct application of indigenous phosphate rock viable alternative. Laboratory and greenhouse studies were carried out to monitor the effect of the decomposition of legume biomass on the solubilization of Ogun phosphate rock (OPR) on slightly acidic soils. Surface soil samples collected from three experimental sites in SW Nigeria were used. The fertilizer treatments were four rates of P as OPR (0, 30, 60, and 90 kg ha–1) and one rate of triple superphosphate (TSP, 40 kg P ha–1). The legume treatments were cowpea (Vigna unguiculata L Walp) and mucuna (Mucuna puriens L). Rice (Oryza sativa) was used in the greenhouse study as the test crop. Soil samples were analyzed for soluble P and pH after 2, 4, 6, and 10 months of incubation in the laboratory while plant tissues collected from greenhouse study were analyzed for P. In the incubation study, significant increase in water‐soluble P was observed when legume biomass was incorporated with phosphate rock at p < 0.05. Highest value in rice dry‐matter yield was recorded with pots treated with mucuna and TSP, also treatment combination of cowpea and OPR significantly increased rice dry‐matter yield by 16% over pots treated with cowpea biomass alone and 42% over control pot (no legume biomass and OPR in the green house (p < 0.05). Thus incorporation of legume biomass significantly increased rate of OPR solubilization.  相似文献   

3.
Increased phosphorus (P) efficiency is needed to sustain agriculture productivity on soils with low available P. Significant differences were found among Brassica cultivars for growth, P utilization, and remobilization under P deficiency (see our companion paper, Aziz et al., 2011a). To identify the possible mechanisms of P acquisition from low soluble P compounds, four cultivars (‘Rainbow’, ‘CON-1’, ‘Dunkeld’, and ‘Peela Raya’) were selected to ascertain the relationship of their differential P acquisition and growth with their root length in soil and with organic acid release pattern in solution culture experiments. For this purpose their growth and P acquisition from phosphate rock (PR) was compared with calcium di-hydrogen phosphate (Ca-P) when adding uniform dose of 100 mg P kg?1 soil separately from the two sources. Biomass accumulation, root length, root fineness, plant P uptake and ash alkalinity was significantly (P < 0.01) different in plants of all the four cultivars when supplied with PR or Ca-P in soil. Minimum biomass produced by ‘Peela Raya’ grown with either P source was followed by ‘CON-1’, ‘Dunkeld’, and ‘Rainbow’ in ascending order. Shoot dry matter production had a significant positive correlation with root dry matter production (r = 0.85, P < 0.01), root length (r = 0.59, P < 0.05) and root P uptake (r = 0.95, P < 0.01). Cultivars varied significantly for organic acid secretion in solution culture experiment. Higher quantities of secreted citric acid, malic acid and tartaric acid in solution culture experiment were measured for ‘Rainbow’ and ‘Dunkeld’ cultivars. Efficient performance of these two cultivars for growth and P uptake was associated with their longer roots and more secretion of organic acids especially citric acid.  相似文献   

4.
不同改良剂降低矿区土壤水溶态重金属的效果及其长效性   总被引：8，自引：1，他引：8  
为了解施用不同种类改良剂对降低矿区土壤重金属移动性的长期效果,进行为期6年的模拟试验,用化学提取方法评价磷灰石、农用石灰、坡缕石、钙镁磷肥、沸石、猪粪和水稻秸秆7种常用改良剂对降低土壤重金属溶解性的影响。结果表明,农用石灰、钙镁磷肥、磷灰石、坡缕石和沸石对降低矿区土壤水溶态重金属均有良好的效果,但猪粪和水稻秸秆有机物改良剂的效果较差。降低土壤水溶态Cd的效果以钙镁磷肥为最佳(平均可降至29%),降低土壤水溶态Cu的效果以坡缕石为最佳(平均可降至65%),降低土壤水溶态Pb的效果以磷灰石、石灰和钙镁磷肥3种改良剂为佳(平均可降至27%左右);降低土壤水溶态Zn的效果以钙镁磷肥为最佳(平均可降至48%)。磷灰石和沸石对土壤重金属的稳定性有较长的作用效果,坡缕石、石灰和钙镁磷肥对土壤重金属稳定性随试验时间增加有明显的下降;有机物类改良剂对土壤重金属的稳定效果较差,且随有机物质的降解,其稳定效果显著下降。  相似文献   

5.
Abstract

Most agricultural soils in the Indian River area, South Florida, are sandy with minimal holding capacity for moisture and nutrients. Phosphorus (P) leaching from these soils has been suspected of contributing to the eutrophication of surface waters in this region. Dolomite phosphate rock (DPR) and N‐viro soil are promising amendments to increase crop production and reduce P loss from sandy soils. Soil incubation and greenhouse pot experiments were conducted to examine the effects of Florida DPR–N‐viro soil mixtures on the growth of a horticultural crop in an acidic sandy soil and to generate information for developing a desired formula of soil amendments. Dolomite phosphate rock and N–viro soil application increased soil pH, electrical conductivity (EC), extractable P, calcium (Ca), and magnesium (Mg). N–viro soil had greater effect on soil pH, organic matter content, and microbial biomass than the DPR. Comparatively higher nitrification rates were found in the N–viro soil treatment than the DPR treatment. A systematic decrease in soil‐extractable P was found with increasing proportions of N‐viro soil from the combined amendments. Greenhouse study demonstrated that the application of DPR and N‐viro soil significantly improved dry‐matter yield and increased plant P, Ca, and Mg concentrations of radish (Raphanus sativus L.). Based on dry‐matter yield and plant N uptake, the combined amendments that contained 30% or 20% of DPR materials appear to be optimal but remain to be confirmed by field trials.  相似文献   

6.
Application of some chemical amendments such as diammonium phosphate (DP) and triple superphosphate (TP) to contaminated soils is an effective technique to stabilize Pb and decrease its uptake by plants. A calcareous soil was spiked with the rates of 0, 250, 500, and 750 mg of lead (Pb) kg?1 soil as Pb acetate, treated with 760 mg of P kg?1 soil as DP and TP, and incubated for 120 days. The results showed that available phosphorus (P) increased immediately after addition of DP or TP to soil, but it declined sharply after only a few days of incubation time. Pot experiment was conducted on sorghum and spinach. The accumulation of Pb was significantly (P ≤ 0.05) lower in sorghum than in spinach, and also was lower in soil amended with DP than TP. The decreased Pb accumulation in the plants by application of both amendments was mainly attributed to the formation of chloropyromorphite.  相似文献   

7.
Summary The influence of vesicular-arbuscular mycorrhizae on the efficiency of triple superphosphate and rock phosphate fertilizers was compared in two tropical, acid, P-fixing soils (Ivory Coast) in which the available P was labelled with 32PO inf4 sup3- . Both soils were planted with micropropagated oil palms. The growth reponses to the fertilizer applications were low unless accompanied by VAM inoculation, but both fertilizers were equally available to plants. Isotopic-dilution kinetics analyses indicated that the rock phosphate was solubilized in both soils and there was an enrichment of the labile pool of plant-available P, similar to that with superphosphate. The specific activity and the fraction of P derived from either fertilizer was similar in both mycorrhizal and non-mycorrhizal plants, showing that both absorbed P from the same labile pool of P in the fertilized soils. However, VAM inoculation increased the fertilizer utilization coefficient of plants 2.7- to 5.6-fold, depending on the soil and fertilizer. We conclude that VAM inoculation increases fertilizer efficiency, as much of rock phosphate as of superphosphate, for plants growing in acid, P-fixing soils, and the processes involved are not different for the two fertilizers.  相似文献   

8.
The aim of the study was to appraise various types of phosphate fertilizers (bone meal, superphosphate, triple superphosphate, and potassium orthophosphate) for immobilizing metals and metalloids in mining-impacted soils from Broken Hill, Australia. Soils were rich in metals (Pb, Zn, Cu, and Cd) and metalloids (As and Sb) which were mainly contained in minor to trace amounts of coronadite [PbMn8O16], kintoreite [PbFe3(PO4)2(OH,H2O)6], Pb, and Zn sulfides and sulfates (possibly sphalerite, galena, and anglesite) as well as in unidentified soluble metal-bearing phases. Phosphate stabilization experiments were conducted as kinetic column leaching experiments, and chemical and mineralogical changes were assessed using elemental, sulfur isotope, and XRD analyses as well as electron microprobe phase mapping. The application of phosphate fertilizer to the metal-contaminated topsoils led to mineralogical changes, including the formation of secondary metal-bearing phosphates. The elemental concentrations of leachates were used as a criterion to assess the performance of phosphate treatments. Potassium orthophosphate fertilizer was the most effective amendment for Cd stabilization; superphosphate and triple superphosphate fertilizers were the most effective amendments for Pb stabilization. By contrast, the release of As, Cu, Mn, Sb, and Zn were not significantly suppressed, and in several cases, increased, using bone meal, superphosphate, triple superphosphate, and potassium orthophosphate amendments. This study indicates that in situ phosphate stabilization of mining-impacted soils at Broken Hill would most likely be a complex and impractical undertaking in residential areas due to the risk of substantial metal, metalloid, phosphate, and sulfate release.  相似文献   

9.
Abstract

Quantifying the relative contribution of different phosphorus (P) sources to P uptake can lead to greater understanding of the mechanisms that increase available P in integrated P management systems. The 32P–33P double isotope labeling technique was used to determine the relative contribution of green manures (GMs) and P fertilizers to P uptake by Setaria grass (Setaria sphacelata) grown in an amended tropical acid soil (Bungor series) in a glasshouse study. The amendments were factorial combinations of GMs (Calopogonium caeruleum, Gliricidia sepium and Imperata cylindrica) and P fertilizers [phosphate rocks (PRs) from North Carolina (NCPR), China (CPR) and Algeria (APR), and triple superphosphate (TSP)]. Dry matter yield, P uptake, and P utilization from the amendments were monitored at 4, 8, and 15 weeks after establishment (WAE). The GMs alone or in combination with P fertilizers contributed less than 5% to total P uptake in this soil, but total P uptake into Setaria plants in the GM treatments was three to four times that of the P fertilizers because the GMs mobilized more soil P. Also, the GMs markedly increased fertilizer P utilization in the combined treatments, from 3% to 39% with CPR, from 6–9% to 19–48% with reactive PRs, and from 6% to 37% with TSP in this soil. Both PGM and the other decomposition products were probably involved in reducing soil P‐retention capacity. Mobilization of soil P was most likely the result of the action of the other decomposition products. These results demonstrate the high potential of integrating GMs and PRs for managing P in tropical soils and the importance of the soil P mobilization capacity of the organic components. Even the low‐quality Imperata GM enhanced the effectiveness of the reactive APR more than fourfold.  相似文献   

10.
Thermal utilization of sewage sludge through mono‐incineration or gasification results in phosphorus (P) rich sewage sludge ash (SSA) that must be returned to agricultural production systems to fulfill the need for recycling of P resources contained in wastewater streams. As the plant‐availability of P contained in SSA is low, we propose feeding SSA directly into the production of superphosphate fertilizers, thereby opening a further pathway for the recycling of phosphorus (P) from wastewater streams to agricultural production systems by using available technologies. We carried out laboratory‐scale production of superphosphate test‐products, in which rock phosphate (RP) was partially replaced with SSA (gasification) before digestion with concentrated sulfuric acid, and evaluated these products with regard to the solubility of P in H2O and neutral ammoniumcitrate solution. We further carried out a growth‐chamber experiment (28 d) using maize (Zea mays L. cv. Sulano) as a model plant on a low P (0.4 mg PCAL 100g?1), high pH (7.6) substrate to evaluate plant P availability of the test products. Our laboratory‐scale results show that at least 8% of P from RP can be replaced by P from SSA while maintaining both the high solubility of P in the fertilizer product and the growth of maize compared to pure RP digested with concentrated sulfuric acid. Further substitution of RP through SSA decreased the total P concentration of the test products, as well as the relative amounts of P soluble in H2O and neutral ammoniumcitrate solution, which affected early plant development of maize.  相似文献   

11.
A range of low-molecular-weight organic acids were identified in rhizosphere soil, leaf litter, and poultry manure compost. Laboratory and greenhouse experiments were carried out to examine the effects of seven low-molecular-weight organic acids on phosphate adsorption by soils, and the solubilization and plant uptake of P from soil pre-incubated with monocalcium phosphate and North Carolina phosphate rock. Acetic, formic, lactic (monocarboxylic), malic, tartaric, oxalic (dicarboxylic), and citric (tricarboxylic) acids were used in the study. The addition of organic acids decreased the adsorption of P by soils in the order tricarboxylic acid>dicarboxylic acid>monocarboxylic acid. The decreases in P adsorption with organic acid addition increased with an increase in the stability constant of the organic acid for Al (logK Al). Organic acids extracted greater amounts of P from soils meubated with both monocalcium phosphate and phosphate rock than water did. Although more phosphate was extracted by the organic acids from monocalcium phosphate — than from phosphate rock — treated soils in absolute terms, when the results were expressed as a percentage of dissolved phosphate there was little difference between the two fertilizers. The amount of P extracted by the organic acids from both fertilizers increased with an increase in logK Al values. The addition of oxalic and citric acids increased the dry matter yield of ryegrass and the uptake of P in soils treated with both fertilizers. The agronomic effectiveness of both fertilizers increased in the presence of organic acids and the increase was greater with the phosphate rock than with the monocalcium phosphate. The results indicated that organic acids increase the availability of P in soils mainly through both decreased adsorption of P and increased solubilization of P compounds.  相似文献   

12.
The objective of this work was to assess the changes of soil P fractions by Lotus corniculatus and to determine contribution of each fraction to plant P nutrition. Phosphorus was added at a rate of 240 mg/pot as triple superphosphate (20% P), phosphate rock (13% P), or poultry litter (2% P) to a Vertisol or an Inceptisol; a control treatment (without P fertilizer) was also included. Then, L. corniculatus was sowed and harvested eight times; both yields and P content of plant were determined at each harvest. Soil P fractions were determined by Hedley’s modified method. The content of labile and moderately labile P [anionic exchange membrane-Pi (AEM-Pi), NaHCO3-Pi, and NaOH-Pi] fractions were markedly reduced and were probably due to P uptake by plants. The content of the HCl-Pi fraction of the phosphate-rock-treated soil decreased whereas that of the residual P fraction was not modified. The content of organic forms increased in all treatments. The content of both labile organic P and moderately labile organic P were positively and significantly correlated with the P concentration of roots and with roots biomass, suggesting that the increase in these two organic fractions was related to root production. AEM-Pi accounted for 95% and 84% of absorbed P in Vertisol and Inceptisol, respectively.  相似文献   

13.
Abstract

In order to study the effects of repeated phosphate fertilization under protected cultivation, tomato (Lycopersicon esculentum Mill.), radish (Raphanus sativus L.), celery (Apium graveolens L.), and lettuce (Lactuca sativa L.) plants were grown in subsequent cycles on the same substrate and fertilized with increasing amounts of superphosphate containing varying amounts of heavy metals. The accumulation of metals in the soil and the consequent increased uptake of metals by plants did not result in any reduction in the marketable production. The reduced plant yield observed in lettuce and in radish with the increase in the addition of superphosphate was most likely due to the increased salinity of the growth substrate, which affected the metabolic processes of the plants. The high concentration of salts as a result of the addition of high amounts of phosphorus fertilizer made it unadvisable to reuse the substrate under the experimental conditions adopted.  相似文献   

14.
Recycled phosphorus (P) fertilizers from sewage sludge can contribute to the ongoing effort of closing the P cycle. Five recycled P fertilizers (Struvite SSL, Struvite AirPrex®, P‐RoC®, Pyrolysis coal, and Na‐SSA) were tested for their P availability in a two‐year field experiment with maize. The experiment was conducted on an organic certified research station at soil pH 6.5. Other P fertilizer treatments included: phosphate rock (PR), compost, and an unfertilized control. In addition, the rhizobacteria strain Bacillus sp. Proradix (Proradix®) was applied to test its ability to increase P bioavailability. Each year, shoot DM and P offtake of maize was measured and P use efficiency of the tested fertilizers was calculated. No significant differences in shoot DM were found among fertilized treatments and the unfertilized control in both years of experiment. Fertilization with recycled fertilizers increased P offtake by between 0% (Na‐SSA) and 27.5% (Struvite SSL) compared to the unfertilized control. Rhizobacteria application led to an increase in P offtake of maize from 25.9 to 38.7 kg P ha?1 when combined with PR fertilization in the year of fertilizer application, while no significant effect was found for the recycled fertilizers. Some of the tested recycled fertilizers from urban waste water can be considered as effective fertilizers for their use in organic agriculture.  相似文献   

15.
Abstract

The agronomic effectiveness of Mussoorie phosphate rock (MPR) from India and a 2:1 mixture of MPR and single superphosphate (SSP) was compared against SSP as phosphate fertilizers for crops. The experiment was conducted for three seasons and was designed to study the response of crops to current application as well as residual effects of the various P fertilizers. Three crops were grown in sequence: finger millet (Eleusine coracana), maize (Zea mays L.), and blackgram (Phaseolus mungo) on a calcareous soil under irrigated conditions. The phosphate fertilizers were applied to finger millet and/or maize but not to the blackgram. Soil samples were collected at intervals and analysed for Olsen bicarbonate‐extractable P. The agronomic effectiveness of fertilizers relative to SSP (RAE) were calculated from the fertilizer substitution ratios. When used on finger millet, the RAE of MPR, calculated at a yield which corresponded to 90% of calculated maximum yield on applying SSP, was 42%. For the mixture of MPR and SSP the RAE was 68%. On maize, yield in MPR treatment plateaued at too low a level (about 80% of calculated maximum yield for SSP) to calculate RAE but for MPR/SSP the RAE was 80%. The residual effectiveness of fertilizers on the second crop, compared against freshly applied SSP was 41% for SSP, 49% for MPR, and 73% for MPR/SSP. Olsen bicarbonate‐extractable P values determined one month after fertilizer application increased over control by about 55% in MPR and 86% in MPR/SSP treatments relative to SSP. Economic calculations indicated that, application of MPR is of equal value to SSP for the cropping sequence whereas MPR/SSP for the cropping sequence as well as for individual crops.  相似文献   

16.
We evaluated the ability of Brassica napus L. (oilseed rape), Helianthus annus L. (sunflower), and Glycine max L. (soybean) plants grown inoculated with or without bacteria to utilize organic P sources. Plants were supplied with inorganic (dibasic sodium phosphate) and organic P sources (phytate and glucose phosphate) at three concentrations and grown for 40 d under sterile conditions. Three inoculation treatments were compared: control (non‐inoculated plants), inoculation with Bacillus amyloliquefaciens BNM340, and inoculation with Pseudomonas fluorescens BNM296 (two bacteria with proven phytase activity). Oilseed rape, sunflower and soybean could utilize organic P sources. For example, when phytate (0.5 mM) P was used as the external P source, the increase factors over the no‐P treatments were 4.5, 1.4, and 1.4 for oilseed rape, sunflower, and soybean P uptake, respectively. When glucose 1‐phosphate disodium salt (G1P, 0.5 mM) was the P source, the increase factors were 8.8, 1.7, and 1.9 respectively. Positive responses to the organic P sources were found for the biomass accumulation of oilseed rape and soybean but not for sunflower. The inoculation with bacteria did not exert a promoting effect on P uptake. We demonstrate that the three species can effectively use organic P sources. The existence of crop plants that are more efficient in the utilization of different soil P sources would be particularly beneficial to improve P recycling and use of P fertilizers in agriculture.  相似文献   

17.
Abstract

The quality of phosphate rock (PR) is declining and the use of lower quality PR results In lower water‐soluble and higher citrate‐soluble P in the fertilizer product. A greenhouse study was conducted to evaluate the plant availability of P in commercial superphosphate fertilizers having various levels of water‐soluble P. Seven commercial fertilizers, Including 6 granular concentrated superphosphates and one normal superphosphate, were evaluated. Reagent grade monocalcium phosphate served as a control. The fertilizers were manufactured from PR deposits located in the United States (Florida, Idaho and North Carolina) and Morocco. Water‐soluble P ranged from 77 to 92 X of the total fertilizer P. Citrate‐soluble, water‐insoluble P ranged from 7 to 20 % of the total fertilizer P. Four of the 5 American fertilizers had a lower percentage of water‐soluble P as compared to the concentrated superphosphate from Morocco. Fertilizers manufactured from U.S. phosphate deposits contained an average of 6 times more Fe and 4 times more Al than the Moroccan concentrated superphosphate.

Each source was added to a Mountvlew slit loam soil (pH = 6.5) at rates to supply 0, 10, 20, 30, 40 and 50 mg P kg‐1soil (0, 22.9, 45.8, 68.7, 91.6, and 114.5 ppm P2O5, respectively). Sorghum‐sudangrass (Sorghum bicolor) was harvested at 28 and 56 days after planting in the treated soil. Herbage yields and the P concentration in harvested forage were not affected by the source of added P. The effect of the rate of added P on forage yield and P concentration was described by polynomial regression. The granular concentrated superphosphate fertilizers used in this study contained ≥ 80 % of their plant available P in a water‐soluble form and were as effective as reagent grade monocalcium phosphate. Thus the level of water‐soluble P that will be required to reduce the performance of a fertilizer is lower than the levels currently found in American commercial concentrated superphosphates  相似文献   

18.
Abstract

The agronomic effectiveness of five partially acidulated phosphate rocks (PAPRs) and an unground phosphate rock (PR) were compared against single superphosphate (SSP) in a glasshouse experiment using a high phosphorus (P) retention soil at a near‐neutral pH (pH 6.5), and corn (Zea mays L.) as the test crop. The PAPRs were prepared by acidulating unground North Carolina PR with either phosphoric or sulphuric acid (expressed as Phos‐PAPR and SA‐PAPR, respectively) and at three levels of acidulation (20, 33, and 50%). The relative agronomic effectiveness (RAE) and substitution value (SV) of the test fertilizers, calculated with respect to SSP using the standard “vertical”; and “horizontal”; comparisons, showed that 50% phosphoric acidulated PAPR performed as effectively as SSP whereas the other fertilizers were less effective. The PR treatment showed a small yield response. The dry matter yield and P uptake were linearly related to water‐soluble P of the fertilizers up to 66% of total P and there was no advantage in acidulating fertilizers above this level of water‐soluble P using reactive PR. Whereas very little of the directly‐applied PR dissolved (3.4% of PR applied), PR applied as a component of PAPRs dissolved up to 22%. The dissolved proportion of added PR component increased with increasing water‐soluble P content of the fertilizer. The results suggest a greater efficiency of PAPR than SSP as a P supplier to plants.  相似文献   

19.
The aim was to investigate different organic fertilizers derived from plant materials with respect to their nitrogen and carbon turnover in soil in comparison with organic fertilizers derived from animal‐waste products. In a 64‐day incubation study at 5°C and 15°C, the following fertilizers were used: coarse faba bean–seed meal (Vicia faba L.), coarse meals of yellow and white lupin seeds (Lupinus albus L. and Lupinus luteus L.), Phytoperls® (waste products of maize [Zea mays L.] processing), coarse meal of castor cake (Ricinus communis L.) as a widely used organic fertilizer, and horn meal as a reference fertilizer‐derived from animal waste products. At 15°C, horn meal showed the highest apparent net N mineralization of fertilizer‐derived N, followed by castor cake and the two lupin meals. At 5°C, apparent net N mineralization of fertilizer‐derived N from horn meal and coarse meal of yellow lupin seeds was nearly identical, followed by castor‐cake meal. Net N mineralization from legume‐seed meals showed no or even a negative temperature response, at least temporarily. In contrast, the other fertilizers showed a positive temperature response of net N mineralization. The content in recalcitrant structural components and the decoupling of decomposition of N‐rich and C‐rich tissue components in time are discussed as controlling factors of fertilizer‐N turnover at low temperature. Microbial residues seem to be an important temporary sink of fertilizer‐derived C and N. Legume‐seed meals induced considerable N‐priming effects. Temperature induced differences in the decomposition of total fertilizer C, indicated by changes in the sum of cumulative CO2‐C evolution, total K2SO4‐soluble organic C and microbial‐biomass C were much smaller than indicated by cumulative CO2‐C evolution alone. Our results indicate that legume‐seed meals have the potential to replace horn meal and castor‐cake meal in organic vegetable production, especially when soil temperatures in early spring are still low.  相似文献   

20.
The effects of farmyard manure (FYM), Tithonia diversifolia (tithonia) and urea when applied alone or in combination with Minjingu phosphate rock (MPR), Busumbu phosphate rock (BPR) or triple superphosphate (TSP) on soil acidity, P availability, maize yields and financial benefits were evaluated at Bukura and Kakamega in western Kenya. A reduction in exchangeable acidity and Al was observed in most tithonia- and FYM-treated soils, but not with inorganic P sources when applied in combination with urea. The effectiveness in increasing available soil P followed the order; TSP > MPR > BPR among inorganic P sources, and FYM > tithonia among organic materials at both sites. At Bukura, a site higher in both available P and Al saturation compared with Kakamega, maize did not respond to inorganic P sources applied in combination with urea. Maize, however, responded when inorganic P sources were applied in combination with FYM or tithonia at this site. At Kakamega, maize responded to TSP but not to MPR or BPR when applied with urea. Application of TSP in combination with tithonia gave the highest maize yields at both sites. Of the tested technologies, only FYM when applied alone at Bukura was economically attractive.  相似文献   

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