Addition Of Superphosphate Research Articles

Dissolving mechanism of strain P17 on insoluble phosphorus of yellow-brown soil.

Strain P17 was a bacterial strain identified as Bacillus megaterium isolated from ground accumulating phosphate rock powder. The fermentation broth of strain P17 and the yellow-brown soil from Nanjing Agricultural University garden were collected to conduct this study. The simulation of fixed insoluble phosphorous forms after applying calcium superphosphate into yellow-brown soil was performed in pots, while available P and total P of soil were extremely positive correlative with those of groundwater. Then the dissolving effect of strain P17 on insoluble P of yellow-brown soil was studied. Results showed that Bacillus megaterium strain P17 had notable solubilizing effect on insoluble phosphates formed when too much water-soluble phosphorous fertilizer used. During 100 days after inoculation, strain P17 was dominant. Until the 120th day, compared with water addition, available P of strain P17 inoculation treated soil increased by 3 times with calcium superphosphate addition. Besides available P, pH, activity of acid and alkaline phosphatase and population of P-solubilizing microbes were detected respectively. P-solubilizing mechanism of P-solubilizing bacteria strain P17 seems to be a synergetic effect of pH decrease, organic acids, phosphatase, etc.

Relative effectiveness of indigenous populations of vesicular-arbuscular mycorrhizal fungi from four sites in the Negev

ABSTRACT Vesicular-arbuscular mycorrhizal (VAM) fungi indigenous in the soil of the semi arid northern Negev of Israel greatly enhanced phosphorus (P) uptake of mycorrhizal pepper plants in three out of four soils tested and at four P levels. In a calcareous loess soil, additions of superphosphate equivalent to 3,000 kg ha−1 could not alleviate the absence of the VAM association. Increasing internal leaf P levels were correlated closely with a stimulation of flower bud production in pepper. Subsequent planting of onion in the same soils with no further P addition revealed the total dependency of this species on the VAM symbiosis. Mycorrhizal infection reduced by half the R/S ratios of onion plants, mainly by the enhancement of shoot growth. Results indicate the presence of a highly efficient VAM population in the loess soil. These findings are considered with regard to the evolution of the mycorrhizal association and its effect on plant morphology and physiological processes.

Effect of Superphosphate as Additive on Nitrogen and Carbon Losses during Pig Manure Composting

A pilot scale experiment of composting in rotting boxes used pig manure with cornstalks was carried out to study the effects of superphosphate on nitrogen and carbon losses including gas emissions. Besides control, there were five amended treatments with superphosphate addition (counted by P content) at 0.05, 0.10, 0.15, 0.20 and 0.25 molar ratio of initial nitrogen. The results indicated that superphosphate addition decreased ammonia volatilization, total nitrogen and carbon losses in composting. Total nitrogen losses of superphosphate-amended treatments were reduced by 9.3%, 14.6%, 30.1%, 45.8% and 71.5%, respectively. About 0.8% to 1.2% of initial nitrogen lost in the form of N2O emission, and the CH4 emission accounted for less than 0.3% of initial carbon. More than 0.15 molar ratio of superphosphate in compost materials caused considerable adverse effects on degradation of organic matter.

Turnover of Manure 15N‐Labelled Ammonium during Composting and Soil Application as Affected by Lime and Superphosphate Addition

To determine N turnover and losses during aerobic composting of animal manure, a 41‐d laboratory study was performed on pig manure composting with three additive treatments (Straw: pig manure + straw only; Lime: pig manure + straw + quick lime; and SSP: pig manure + straw + single superphosphate). The NH4–N pool in the pig manure was initially labeled with 15N to determine the fate of manure NH4–N during composting. The composts were subsequently applied to soil to investigate the effects on soil mineral N and to trace the 15N during 60 d of incubation at 25°C. Of the initial manure 15NH4–N, approximately 30, 90, and 20% was lost by NH3 volatilization during composting in the Straw, Lime, and SSP treatments, respectively. Concurrently, 62, 16, and 41% of initial 15NH4–N was immobilized in the respective treatments. When the composts were applied to soil, the mineral N in soil with SSP compost was higher throughout the incubation than in soil with Straw and Lime composts. This was because of higher mineral N content in the SSP compost on application and higher net N mineralization from that compost in the soil. In soil with Straw compost, N mineralization and immobilization were slow or effectively in balance. In soil with Lime compost, net N immobilization was strong in the first 10 d, but then net N mineralization dominated the remaining period of soil incubation. Overall, adding lime before composting reduced the NH4–N content in the compost and the amount available in soil, while adding superphosphate increased the NH4–N content in both. Therefore, superphosphate addition increased the potential fertilizer value of composted pig manure.

Effects of brown sugar and calcium superphosphate on the secondary fermentation of green waste

The generation of green waste is increasing rapidly with population growth in China, and green waste is commonly treated by composting. The objective of this work was to study the physical and chemical characteristics of composted green waste as affected by a two-stage composting process and by the addition of brown sugar (at 0.0%, 0.5%, and 1%) and calcium superphosphate (Ca(H2PO4)2·H2O) (at 0%, 3%, and 6%) during the second stage. With or without these additives, all the composts displayed two peaks in fermentation temperature and matured in only 30days. Compared to traditional industrial composting, the composting method described here increased the duration of high-temperature fermentation period, reduced the maturity time, and reduced costs. Addition of 0.5% brown sugar plus 6% calcium superphosphate produced the highest quality compost with respect to C/N ratio, pH, organic matter content, electrical conductivity, particle-size distribution, and other characteristics.

Effects of Reed Straw, Zeolite, and Superphosphate Amendments on Ammonia and Greenhouse Gas Emissions from Stored Duck Manure

Stored poultry manure can be a significant source of ammonia (NH) and greenhouse gases (GHGs), including nitrous oxide (NO), methane (CH), and carbon dioxide (CO) emissions. Amendments can be used to modify physiochemical properties of manure, thus having the potential to reduce gas emissions. Here, we lab-tested the single and combined effects of addition of reed straw, zeolite, and superphosphate on gas emissions from stored duck manure. We showed that, over a period of 46 d, cumulative NH emissions were reduced by 61 to 70% with superphosphate additions, whereas cumulative NO emissions were increased by up to 23% compared with the control treatment. Reed straw addition reduced cumulative NH, NO, and CH emissions relative to the control by 12, 27, and 47%, respectively, and zeolite addition reduced cumulative NH and NO emissions by 36 and 20%, respectively. Total GHG emissions (as CO-equivalents) were reduced by up to 27% with the additions of reed straw and/or zeolite. Our results indicate that reed straw or zeolite can be recommended as amendments to reduce GHG emissions from duck manure; however, superphosphate is more effective in reducing NH emissions.

Inorganic Materials as Ameliorants for Soil Remediation of Metal Toxicity to Wild Mustard (Sinapis arvensis L.)

The ameliorating effects of different inorganic materials were investigated on a soil originating from a zinc smelter dumping site contaminated by toxic metals. Wild mustard (Sinapis arvensis L.) was used as a test plant. The soil was amended with different doses of mining sludge, Perferric Red Latosol (LVj), steel shots, cyclonic ash, silifertil, and superphosphate. The most effective amendments improved plant growth with 45% and reduced metal uptake by over 70% in comparison to untreated soil. Reductions in availability as estimated by BaCl2-extractable metals reached up to 90% for Zn and 65% for Cd as compared to unamended soil. These reductions were associated with lower shoot and root metal contents. Shoot Zn content was reduced from 1,369 μg g−1 in plants grown on untreated soil to 377 μg g−1 when grown on cyclonic ash amended soil while Cd decreased from 267 to 44 μg g−1 in steel shots amended soil. Superphosphate addition had no ameliorating effect. On the contrary, it increased BaCl2-extractable amounts of Zn. Considering all parameters we determined, steel shots, cyclonic ash and silifertil are the most promising for remediating metal contaminated soil in the tropics. Further studies evaluating impacts, cost-effectiveness and durability of effects will be conducted.

Nitrogen turnover and loss during storage of slurry and composting of solid manure under typical Vietnamese farming conditions

SUMMARYA high proportion of plant nutrients present in animal feed are excreted and therefore animal manure can be an important source of nitrogen (N) for crop production if losses of plant nutrients to the environment during storage and processing are minimized. The present study examines gaseous N losses from stored pig slurry and during composting of solid manure as affected by protein and fibre content in the feed and manure management. Two slurry storage treatments (with and without cover) and three additives to solid manure composting (straw only, straw+lime and straw+superphosphate) were examined for three common types of pig feed in Vietnam (low-protein high-fibre, medium-protein medium-fibre and high-protein low-fibre).Feed type was found to affect the N content in pig slurry or manure and thus potential N losses. The fraction of N loss caused by N emission from covered slurry storage was 0·25–0·30 of initial N content, while that from uncovered slurry was 0·60–0·70. After 90 days of storage, 1·15–1·20 times the initial ammonium-N (NH4-N) was found in the covered slurry and 0·40–0·50 in the uncovered. The fraction of N lost during composting with superphosphate was 0·25–0·35 of initial total N, while with lime or straw the total N loss was 0·45–0·55. With added superphosphate, 1·25–1·60 times the initial NH4-N in manure was found in the compost after 80 days compared with only 0·11–0·22 for lime and 0·22–0·36 for straw only. Covering stored slurry and addition of superphosphate when composting solid pig manure are thus important methods for Vietnamese farmers to minimize N losses and produce compost with a high content of plant-available N.

A COMPARATIVE STUDY FOR IMPACT OF LOW PHOSPHORUS FERTILIZATION IN DIFFERENT COMBINATIONS WITH SULPHUR, GYPSUM AND PHOSPHOREIN ON TOMATO GROWTH, MINERAL STATUS AND PRODUCTIVITY.

Two field experiments were conducted at Kalabshow district, Dakahlia Governorate during two successive summer seasons of 2007 and 2008 to study the effect of phosphorus fertilizers,i.e., super phosphate and rock phosphate in different combination with gypsum, sulphur and phosphorein on growth ,mineral composition and productivity of tomato cv. Super marmand . The experiment included fourteen treatments arranged in randomized complete block design. The treatments contained two sources of phosphorus (P) fertilizers [super phosphate (SP) and rock phosphate (RP) at 100% from recommended dose (RD),i.e,75KgP2O5] and different combination of SP or RP at low rate (65%),i.e,52.5 KgP2O5 of RD) with gypsum (G),sulphur (S)and phosphorein(Phn). The main results were as follows: 1- Addition of super phosphate(SP) at 65 % of the recommended phosphorus rate(RD) with gypsum(G) and phosphorein(Phn) as soil amendment had a significant effect on number of leaves per plant, plant height , roots& shoots and total dry weights per plant as well as relative dry weight (%)during the two seasons. 2-Application of rock phosphate (RP) at 65 % of the recommended phosphorus rate RD) resulted in significant decrease of foliage concentration of N and P as well as the N, P ,K total uptake from N,P,K in both seasons. 3- The highest significant N and P concentration and N, P and K uptake were resulted from application of super phosphate (SP) at 65 %from RD in the presence of gypsum (G) and phosphorein (Phn) at both seasons. 4- Addition of the recommended phosphorus rate as super phosphate(SP) or applying (SP) at 65% from RD with gypsum and phosphorein showed the most superior effect regarding average fruit weight, number of fruits and fruit yield of tomato plant as well as total yield per feddan. 5- Application of super phosphate (SP) at 65 %with gypsum (G) and phosphorein (Phn) resulted in 6.45 % increment in the total yield comparing to the control treatment (average of the two seasons) . 6- Applying super phosphate (SP) at 65% from RD with gypsum (G) and phosphorein (Phn) showed the superior significant values for most fruit quality, i.e., T.S.S %, Vit C and total carbohydrates content of tomato fruits. In general, this study demonstrated that it is possible to produce highest growth, yield and quality of tomato plants by applying super phosphate at 65 % of the recommended phosphorus rate with 2.5 ton/feddan of gypsum and 1 kg/feddan of phosphorein. Moreover, the phosphatic fertilization can be reduced by 35 % of the recommended rate beside reduction of chemical pollution.

INTERACTIONS BETWEEN ORGANIC AMENDMENTS AND PHOSPHATE FERTILIZERS MODIFY PHOSPHATE SORPTION PROCESSES IN AN ACID SOIL

To determine how organic amendments and phosphate fertilizers interact to modify P sorption processes, three phosphate fertilizers were applied to lignite- and compost-amended acid soil and incubated for either 3 or 26 days. The fertilizers applied were potassium dihydrogen phosphate, triple superphosphate, and diammonium phosphate (DAP). After 3 days of incubation, sorption of all three P sources was decreased in the lignite-amended treatments, whereas P sorption was increased in the compost-amended treatments. Increased incubation time (26 days) resulted in significantly decreased P sorption when DAP was added to lignite-amended treatments. Addition of triple superphosphate increased P sorption in lignite- and compost-amended treatments and decreased solution pH compared with DAP application. In addition to the effect of P source, differences in P sorption between the lignite- and compost-amended treatments were driven by differences in solution chemistry, predominantly solution pH and cation dynamics. Soil amendment and fertilizer addition also increased microbial activity in the incubation systems, as measured by carbon dioxide respiration. It is proposed that the combination of lignite and DAP may contribute to decreased P sorption in acid soils, with the positive effects likely caused by both chemical and biological processes, including the formation of soluble organic-metal complexes.

N 2O emission from the semi-arid ecosystem under mineral fertilizer (urea and superphosphate) and increased precipitation in northern China

Soil management and climate change affect N 2O emission significantly. The semi-arid grassland in northern China is under strong anthropogenic disturbance (fertilization and land use) and toward a 30% increase in precipitation in future. To investigate their impacts on N 2O emission, N 2O fluxes were measured monthly in the grassland and abandoned cropland under mineral fertilizer (urea and superphosphate) and increased precipitation during the growing season. During the measured period, WFPS (water filled pore space) from all the treatments never exceeded 70%, suggesting that nitrification was the predominant source of N 2O for all the treatments. Increased precipitation induced an additional growing season emission of 0.28–0.30 kg N 2O-N ha −1 y −1. N 2O emission increased linearly with nitrogen application rate and emission factors (EFs) for grassland and abandoned cropland averaged 0.35% and 0.52%, respectively. Superphosphate addition induced N 2O emission from abandoned cropland ( P<0.05), but had no significant effect in the grassland ( P>0.05). Despite of substantial differences in soil properties, N 2O emissions were not significantly different between the grassland and abandoned cropland ( P>0.05). Increased precipitation and nitrogen application at 15 g N m −2 y −1 across the grassland and abandoned cropland of northern China will increase the growing season emissions of 71.4–76.5 and 139.23 Gg N 2O-N into atmosphere annually. These increased emissions are about 40% and 75% of the annual emission of 186.15 Gg N 2O-N from untreated soils, respectively. Therefore, in the temperate semi-arid ecosystem, abandoned cropland does not constitute a potent source for increasing N 2O while the effect of nitrogen fertilization and increased precipitation cannot be neglected from the regional or national emission.

Differential responses of litter decomposition to increased soil nutrients and water between two contrasting grassland plant species of Inner Mongolia, China

Soil chemistry and physical conditions are the key factors controlling litter decomposition. We studied the effects of increased soil nitrogen (N), phosphorus (P), and water on the decomposition rates and associated nutrient dynamics of two dominant grassland plant species (i.e. Allium bidentatum Fisch. ex Prokh. & Ikonn.-Gal. and Stipa krylovii Roshev.) with contrasting life forms and tissue chemistry in a typical steppe of Inner Mongolia, China. The treatments included addition of urea at the rates equivalent to 0, 8, 16, and 32 gN/m 2, and additions of mixed urea and triple superphosphate at the rates equivalent to 0, 8 gN/4 gP, 16 gN/8 gP, and 32 gN/16 gP/m 2, with and without water added. We found marked differences between the two species in the rates, as well as in the responses to water and addition rates of N and P, of litter decomposition. Additions of N alone or in mixture with P stimulated the rate of litter decomposition in both species. Adding water significantly increased the values of decay constant, k, in A. bidentatum, but not in S. krylovii. N and P concentrations in litters of A. bidentatum and S. krylovii all increased corresponding to increases in the rates of N or mixed N and P additions. Our results clearly indicate that the decomposition of high quality litter is more likely to be limited by soil moisture regimes, while that of low quality litter is more sensitive to nutrient availability. Our findings suggest that plant species with different litter qualities should be taken into consideration when we are to model the carbon cycle and nutrient dynamics in grassland ecosystems and that A. bidentatum is expected to contribute more than S. krylovii to the carbon cycle and nutrient dynamics of the semi-arid grasslands of Inner Mongolia.

Effects of several common chemical fertilizers on Tolypothrix scytonemoides (Gardner) Geitler

Good growth of Tolypothrix scytonemoides (Gardner) Geitler was observed in low concentrations of NPK fertilizer, single superphosphate, and urea. Protein content decreased in cells grown in higher concentrations of tested tested chemical fertilizers. Phycobilin pigment contents were enhanced in cells grown in medium amended with NPK fertilizer but were lower in cells grown in 15 and 20 mg·L−1 of single superphosphate and 10, 15, and 20 mg·L−1 of urea. The rates of photosynthetic oxygen evolution and respiratory oxygen consumption were enhanced in cells grown in medium amended with all different concentrations of NPK fertilizer and low concentrations of single superphosphate. Nitrogenase activity was completely inhibited by 20 mg·L−1 NPK fertilizer and 15 mg·L−1 urea but it remained unaffected with the addition of single superphosphate. On one hand, glutamine synthetase activity decreased gradually in a dose-dependent manner in cells grown in NPK fertilizer and urea-amended medium, on the other hand, the cells grown in 10 mg·L−1 single superphosphate exhibited the highest glutamine synthetase activity. Greatest exogenous carbohydrate release was observed in cells grown in 15 mg·L−1 urea.

Efeito de condicionadores químicos na cama de frango sobre o desempenho de frangos de corte

Estudou-se o efeito de condicionadores químicos na cama de frango sobre o desempenho de frangos de corte criados em três lotes consecutivos. Foram utilizadas 1320 aves, 440 em cada lote, em delineamento experimental em blocos ao acaso, com cinco tratamentos (Trat. 1 - cama sem tratamento; Trat. 2 - cama tratada com sulfato de alumínio; Trat. 3 - cama tratada com gesso agrícola; Trat. 4 - cama tratada com superfosfato simples e Trat. 5 - cama tratada com cal hidratada) e quatro repetições. As aves e as rações foram pesadas no início e no final do período experimental para obtenção do peso final, do consumo de ração, da conversão alimentar e da viabilidade. O uso dos condicionadores não influenciou (P&gt;0,05) o peso final, o consumo de ração e a conversão alimentar. A adição do sulfato de alumínio e do superfosfato simples reduziu (P&lt;0,05) a viabilidade das aves. Não é necessário o uso dos condicionadores na cama de frango reutilizada até o terceiro lote.

Monitoring long‐term changes in reserve potassium in some New Zealand soils using a modified sodium tetraphenyl‐boron method

Changes in reserve‐K status were measured on a number of historical and current pasture trials using a modified sodium tetraphenyl‐boron incubation method (TBK incubation). Trials included four P, K, and S trials from North Otago, a long‐term (>40 years) P fertiliser trial from Canterbury (Winchmore), a long‐term (>20 years) nutrient depletion trial from Manawatu, and a 2‐year N × K trial from Southland. While only two trials showed a clear DM response to K, testing by both the original (Jackson's) test and the TBK‐incubation method showed changes in soil K status for all soils. The long‐term fertiliser trial showed that K reserves declined with normal annual superphosphate additions when no K fertilisers were applied. Failure of net changes in K reserve status to adequately account for K removal in nutrient budgets appeared to be best explained by significant plant uptake of K below the soil sampling zone (0–75 mm). Prediction of a dry matter K response when exchangeable‐K levels are near or below critical levels i.e., at Quicktest K (QTK) values < 6–7, is governed by the buffering capacity of soil K reserve. This was linked in this study to measures of both readily available (short incubation; 1–20 h) and long‐term available (168‐h) K. Soils with a large long‐term K reserve can still exhibit a K response under high K demand, but this occurred in only one trial when QTK values were 3 or less, and when short‐term available K was also low. The biphasic nature of K release underlies the complications of predicting K response in many sedimentary soils. The main means of classifying and predicting K response in New Zealand has historically been from Metson's soil class Kc values. This study showed that K reserve status for a significant number of New Zealand soils is not adequately represented by these values, and that better prediction of K response could be achieved using the new TBK‐incubation method after optimisation against field trial data. Implications for using this method to advance routine soil testing of K are discussed.

PERSISTENCE AND DEGRADATION OF COUMAPHOS IN MODEL CATTLE DIPPING VATS

The stability of coumaphos [O,O-diethyl O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7 yl)phosphorothioate] was studied in model dipping vats under field conditions using 14C-labelled and unlabelled coumaphos, with or without additives. The stability of coumaphos in model vats increased significantly by maintaining a pH of 5 by addition of superphosphate. Copper sulphate amendment did not seem to have any additional effect on stability. Potasan was the major metabolite in addition to chlorferon and 4-methylumbelliferone. Coumaphos concentration was doubled in the sediment of vat treated with copper sulphate as compared to the control vat as a result of emulsion breakdown. Chlorferon was the only metabolite detected in the sediment of the former vat indicating inhibition of the anaerobic degradation.

Chemical changes in argisols under irrigated grape production in the central São Francisco river valley, Brazil

This study compares the chemical composition of the solution and exchange complex of soil in a 3-year-old irrigated vineyard (Vitis vinifera L., Red Globe cultivar) with that of adjacent clearing in the native hyperxerophyllic 'caatinga' vegetation. The soils are classified as Plinthic Eutrophic Red-Yellow Argisol; according to Soil Taxonomy they are isohyperthermic Plinthustalfs. Detailed physiographic characterization revealed an impermeable gravel and cobble covering the crystalline rocks; the relief of this layer was more undulating than the level surface. Significant higher concentrations of extractable Na, K, Mg and Ca were observed within the vineyard. Lower soil acidity, higher Ca/Mg ratios, as well as lower sodium adsorption and Na/K ratios reflected additions of dolomitic lime, superphosphate and K-bearing fertilizers. As the water of the São Francisco River is of good quality for irrigation (C1S1), the increases in Na were primarily attributed to capillary rise from the saline groundwater table. None of the soil in the study area was found to be sodic. About 62% of the vineyard had an Ap horizon with salinity levels above 1.5dSm-1 (considered detrimental for grape production); according to average values for this horizon, a potential 13% reduction in grape production was predicted. Differences in chemical composition in function of distance to the collector canals were observed in the clearing, but not in the vineyard. The influence of differences in the elevations of the surface and impermeable layers, as well as pediment thickness, was generally weaker under irrigation. Under irrigation, soil moisture was greater in points of convergent surface waterflow; the effect of surface curvature on chemical properties, though less consistent, was also stronger in the vineyard.

Mineralização de nitrogênio e enxofre em solos brasileiros sob influência da calagem e fósforo

O presente estudo, desenvolvido em laboratório no período de outubro de 1995 a janeiro de 1996, objetivou avaliar a influência da calagem e fósforo (P) sobre a mineralização de nitrogênio (N) e enxofre (S) em sete solos, com ampla variabilidade nas características químicas e físicas. Os solos (200 g), numa etapa anterior à aplicação de P (KH2PO4 p.a.), foram pré-incubados por sete dias com CaCO3p.a.Aseguir,foramincubadosnovamente,pormais70dias.OsteoresdeN (NO3- + NH4+) e S (SO4(2-)) mineralizados em condições aeróbias foram avaliados a cada catorze dias, e notou-se neles uma dinâmica diferenciada, com o N mineral apresentando maior variação do que o sulfato. As quantidades de N mineralizado não se mostraram dependentes da acidez do solo, porém notou-se uma aceleração na mineralização do N com a calagem do Glei Húmico e do Latossolo Vermelho-Amarelo coletado no Rio de Janeiro. Ao contrário, a mineralização de S no Glei Pouco Húmico e no Latossolo Vermelho-Amarelo coletado no Rio de Janeiro foi influenciada pela correção da acidez do solo, que promoveu maior disponibilidade de sulfato nesses solos. Os teores de N e S mineralizados não foram influenciados pelos níveis de P disponível. A maior prevalência de nitrato e sulfato em alguns dos solos calcariados implica maior cuidado no estabelecimento da época de aplicação de corretivo.

Decreases in Colwell bicarbonate soil test P in the years after addition of superphosphate, and the residual value of superphosphate measured using plant yield and soil test P

Decreases in Colwell bicarbonate soil test P in the years after applying single (ordinary) superphosphate, and the residual value of superphosphate, was measured in a long-term field experiment on a duplex (texture contrast) soil (sand over lateritic ironstone gravel clay sand at 10–15 cm), at Wongan Hills, Western Australia, typical of many soils used to grow crops in Western Australia. Ten levels of P (0–91 kg P ha-1) were applied once only in late May to different plots in different years from 1988 to 1993. Wheat (Triticum aestivum), or lupin ( Lupinus angustifolius)) were sown in late May of each year, when the P treatments applied that year were banded (drilled) with the seed. Soil samples were collected each June to measure soil test P. Seed (grain) yields of the crops were measured each December. The residual value (RV) of P applied in previous years was calculated relative to P applied in the current year, using grain yields (RVyield) and soil test P (RVsoil). Soil test P measured on soil samples collected in June was related to yields measured in December that year to provide soil P test calibrations. Relative to P applied in the current year, soil test P decreased by between 15 to 30% for P applied one year previously, by 25 to 30% for P applied three years previously, and by 60 to 70% for P applied six years previously. Soil test P was affected by spatial variation, and it also varied in the different years, for P applied in the current year, one year previously, two years previously, etc. Compared with P applied in the current year, mean RVyield determined in the different years decreased by about 40% one year after P application, followed by a further 20% decrease for P applied two years previously, followed by a further 20% decrease for P applied three to five years previously. Relative to current P, RVsoil decreased by about 25% one year after P application, followed by a further 20% for P applied two years previously, followed by a further 10% for P applied three years ago, and followed by a further 6% for P applied four and five years ago. As measured in the different years, the soil P test calibration varied between years for P applied one, two etc. years previously. This was so even when the same cultivar of wheat was grown at the same site in different years.

Degradation of atrazine in soil by Streptomyces

Streptomyces sp. PS1/5 was able to degrade atrazine in soil while growing on a mixture of chitin and ground cornstalks as carbon and nitrogen source. The addition of triple superphosphate greatly stimulated the degradation of atrazine by Streptomyces sp. PS1/5, while the addition of lime stimulated the degradation to a lesser degree. Ferrous sulfate had a small positive effect on atrazine degradation. Atrazine in soil was reduced from 20 g g‘1 dry soil (20 ppm) to 6 ppm within 30 days in soil amended with 8% chitin, 2% cornstalks and 0.1% triple superphosphate and incubated at 25°C. The results indicate that it may be possible to use bacteria of the genus Streptomyces to degrade pesticide residues in contaminated soils.