The effect of N,P and KCl fertilizers on grain yield and Cd concentration of malting barley

A three-year field study, conducted on two Orthic Black Chernozemic soils, investigated the effects of application of N, P and KCl fertilizers on grain yield and Cd concentration of two cultivars of malting barley (Hordeum vulgare). Soil levels of N and P were good predictors of the likelihood of a yield response to fertilizer applications, while increases in yield with potassium chloride (KCl) application occurred in spite of high levels of soil K. Additions of ammonium nitrate increased Cd concentration in malting barley when soil nitrate levels were low, with increased Cd concentrations in the grain generally being associated with increasing crop yields. Applications of monoammonium phosphate or KCl tended to increase concentrations of Cd in malting barley, with the significance of the effect varying from year to year. Response of Cd concentration in the grain to P and KCl application was not related to levels of these nutrients in the soil. As the N and K fertilizer used in the study did not contain significant quantities of Cd, the increase in Cd concentration in the grain with fertilizer application was not solely a result of Cd addition as a fertilizer contaminant. The fertilizer salts may increase Cd concentration in the soil solution, increasing availability for crop uptake. Increased crop yield associated with N application may also increase Cd accumulation through increased root interception and enhanced mass flow.     

The movement into soil of P from superphosphate grains and its availability to plants

The movement of P applied as grains of triple superphosphate into two soils (laterite and podzol) of differing P sorption capacities was studied in a laboratory experiment. The availability of this P for plant growth was evaluated by measuring the P desorption characteristics of the fertilized soil and also through a plant growth experiment. Four weeks after fertilizer application to the soil 45% and 72% of the fertilizer P had dissolved for the laterite and podzol, respectively. For both soils all the added P was retained within 80 mm of the fertilizer grain and was considered to occur in the soil in three discrete zones. These zones consist of: (1) the residual grain and a small adjacent zone of soil where most P occurs as insoluble fertilizer compounds and possibly as compounds precipitated from fertilizer solution (2) an inner region where both precipitates and P adsorbed on to the soil at about the maximum adsorption value are present and (3) an outer region where all the added P is adsorbed on to the soil at levels less than the maximum adsorption value.The desorption of fertilizer P from soil in 0.01M CaCl₂ solution at different solution:soil ratios as a function of total soil P followed a relationship of the type Y = aX^b where Y is desorbed P and X is adsorbed P. For both soils the values of exponent (b) decreased and tended to unity as the solution:soil ratio increased. A much higher proportion of total P (1.5–3 fold) was desorbed from the podzol as compared to the laterite.The results of the greenhouse trial showed that P from soil reacted at three P concentrations corresponding to the three discrete zones surrounding fertilizer grains was equally available. This result was obtained for two successive wheat crops for both the soils. When the P fertilized soil was banded it was much more effective (about 3 to 5 times for the laterite and 2 to 3 times for the podzol) than when mixed through the soil.     

Cultivation reduces fertilizer residual effectiveness and affects soil testing for available phosphorus

The agronomic effectiveness of superphosphate and two rock phosphates that had been applied once only to the soil surface 8 to 12 years previously was measured in a field experiment with oats on a lateritic soil in south-western Australia. The soil was either undisturbed or cultivated with a rotary hoe before sowing. The rock phosphates were Christmas Island C-grade ore (C-ore, a calcium ironaluminium rock phosphate), and C-ore calcined (heated) at about 500°C (Calciphos).Cultivation reduced the effectiveness for all three fertilizers by 20 to 50%. The effectiveness of phosphorus (P) applied as superphosphate decreased with increasing period from time of application whereas the effectiveness of the rock phosphates increased but they were always much less effective than superphosphate.The relationship between grain yield and P concentration of plant tissue (i.e. the internal efficiency of P use curve) was similar regardless of fertilizer type, year of application of fertilizer, and whether or not the soil was cultivated. Thus differences in fertilizer residual effectiveness were solely due to the amount of P taken up by the plants.Values of bicarbonate-soluble P (i.e. soil test for P values) for superphosphate treated soil were reduced by about 20 to 25% when the fertilizer was incorporated into the soil whereas for the rock phosphate treated soils the values were little affected by cultivation. The relationship between yield and soil test for P values varied depending on cultivation treatment and fertilizer.We conclude that cultivation decreases the effectiveness of residual fertilizer P and that cultivation and fertilizer type influence the accuracy of yield prediction from soil test values.     

Evaluation of the Bray 1, calcium acetate lactate (CAL), Truog and Colwell soil tests as predictors of triticale grain production on soil fertilized with superphosphate and rock phosphate

In a field experiment in Western Australia, six different levels of three different phosphorus (P) fertilizers (triple superphosphate, TSP; Queensland (Duchess) rock phosphate, QRP; North Carolina rock phosphate, NCRP) were applied at the start of the experiment in 1984. Grain yield of triticale (×Triticosecale) was measured from 1984 to 1988. In February-March of each year from 1985 to 1988, soil samples were collected to measure soil extractable P (soil test values) using four reagents (Bray 1, calcium acetate lactate (CAL), Truog and Colwell). Soil test values were related to triticale grain yields, determined either as absolute yield or percentage of the maximum yield, produced later on in each year. The relationship differed with fertilizer type, reagent and year. All four soil test reagents were equally predictive of yield. It is concluded that these soil P tests provide crude predictions of plant yield regardless of the reagent used.     

Yield and P uptake by wheat as affected by P fertilization and soil moisture regime

The influence of different moisture regimes and the method of phosphate application on the availability and uptake of native and fertilizer P by wheat (Triticum aestivum L.) was studied in a field experiment on sandy loam soil low in available P. Phosphorus application up to 39 kg ha^?1 signficantly increased wheat yield irrespective of the method of application. Wheat yield with drill application of 26 kg P ha^?1 was almost equal to that with broadcast application of 39 kg P ha^?1. A mean increase of 230 kg ha^?1 grains was obtained, when P fertilizer was drilled below seed. The relative efficiencly of placement was found to be 1.4 times that of broadcast method. The increase in IW/PAN-E ratio from 0.6 to 1.0 significantly increased grain yield. Scheduling of irrigation at narrow IW/PAN-E ratio but with fertilizer placed gave almost the same yield as was obtained with irrigation scheduled at IW/PAN-E equal to 1.0 and P fertilizer broadcast. Total P uptake by wheat was greater under wetter moisture regimes. The uptake of applied P decreased with increase in soil moisture regime, while that of soil P tended to increase with frequent irrigation. The uptake of soil P was a linear function of moisture supply and under conditions of this experiment P uptake by wheat beyond a P dressing of 20 kg ha^?1 was limited by soil water.     

Nitrate leaching and soil moisture prediction with the LEACHM model

The LEACHM model developed by Wagenet and Hutson [1989] was used to predict the mineral nitrogen and water content in the soil under a winter wheat crop from February to April in two years and three locations. The model grossly overestimated soil water content, probably due to the bad fitting of the assumed water retentivity function to the experimental data at high water contents, and to the presence of a relatively shallow water table (1.0–1.5m). Measured soil hydraulic conductivity varied with water content in a different manner than predicted by the model. By assuming a sandy or gravelly soil layer between the bottom of the measured soil profile and the water table, prediction of soil water content improved considerably. Simulation showed that, under the experimental conditions studied, soil mineral nitrogen varied mainly due to the fertilizer additions, mineralization and denitrification. Nitrogen uptake by plants and leaching were small. Low values of nitrate leaching were predicted by the model because of low drainage. Large differences between predicted and observed values in the mineral nitrogen in the soil occurred in some cases, both in the total amount and its profile distribution.     

Evaluation of two rock phosphates and a calcined rock phosphate as maintenance fertilizers for crop — pasture rotations in Western Australia

Two long-term (11 and 12 y) field experiments in south-western Australia are described that measured the relative effectiveness of three rock phosphate fertilizers (C-grade ore, Calciphos and Queensland (Duchess) rock phosphate), single, double and triple superphosphate. The experiments were on established subterranean clover (Trifolium subterraneum) — based pasture that had received large, yearly, applications of single superphosphate for many years before the experiments began so that in the first year the nil phosphorus (P) treatment produced 80 to 90% of the maximum yield. The experiments were conducted using a rotation of one year cereal crop (oats,Avena sativa at one site, and barley,Hordeum vulgare, at the other): 2 y pasture, a typical rotation on farms in the region. Five levels of each P fertilizer were applied every third year with the crop. Grain yield of cereals, P content of grain, pasture yield, and bicarbonate-soluble P extracted from the soil (available P) were used to estimate fertilizer effectiveness values.The three superphosphate fertilizers had identical values of fertilizer effectiveness. Superphosphate was always the most effective fertilizer for producing grain. The rock phosphate fertilizers were one-seventh to one-half as effective per kg P as superphosphate when assessed on the yield or P content (P concentration × yield) of grain within each cropping year. Bicarbonate-extractable soil P values demonstrated that superphosphate was two to fifteen times as effective as the rock phosphate fertilizers. The relationship between grain yield and P content in grain (i.e. the internal efficiency of P use curve) was similar for the different P fertilizers. Thus for all P fertilizers yield was not limited by other factors as it varied solely in response to the P content, which in turn presumably depended on the P supply from the fertilizers.The relative agronomic effectiveness of rock phosphates is greater for marginally P deficient soils than for highly P deficient soils but rock phosphate remains less effective than superphosphate. We conclude that the rock phosphates studied should not be substituted for superphosphate as maintenance fertilizers for soils in Western Australia that are marginally deficient in P. This result is consistent with the results of many field experiments on highly P deficient soils in south-western Australia. These have shown that a wide variety of rock phosphate fertilizers are much less effective than superphosphate in both the short and long term.     

The residual value of superphosphate and rock phosphates for lateritic soils and its evaluation using three soil phosphate tests

The residual value of superphosphate and several rock phosphates was measured in three field experiments in Western Australia. The rock phosphates were Christmas Island C-grade ore, calcined C-grade ore (Calciphos) and apatite rock phosphates. The predictive capacity of the Colwell, Olsen and Bray 1 soil tests for phosphate were also evaluated.As measured by yields of variously wheat, oats, barley or clover, the effectiveness of an initial application of superphosphate decreased to about 50% of that of newly applied superphosphate between years 1 and 2, and further decreased to about 20% over subsequent years. At low levels of application, all the rock phosphates were between 10–20% as effective as superphosphate in the year of application for all experiments. Relative to newly applied superphosphate their effectiveness remained approximately constant in subsequent years for two experiments and doubled for the other experiment.The Colwell soil test predicted that the effectiveness of superphosphate decreased to about 45% between years 2 and 3, followed by a more gradual decrease to approximately 15%. At low levels of application, the effectiveness of the rock phosphates as predicted by the Colwell soil test values was initially very low relative to superphosphate (2–30%), and remained low in subsequent years (2–20%). For superphosphate treated soil, the proportion of the added phosphorus extracted generally increased as the level of application increased. By contrast, for rock phosphate treated soil, the proportion of added phosphorus extracted decreased as the level of application increased.For all three experiments there were highly significant positive correlations between amounts of P extracted by the three soil tests. Consequently all soil tests were equally predictive of yield but usually for each soil test separate calibrations between yield and soil test values were required for the different fertilizers and for each combination of fertilizer and plant species and for each year.     

Effect of potassic and phosphatic fertilizer type, fertilizer Cd concentration and zinc rate on cadmium uptake by potatoes

In some areas of southern Australia, cadmium (Cd) concentrations in excess of the Australian maximum permitted concentration (0.05 mg kg^–1 fresh weight) have been found in tubers of commercially grown potato (Solanum tuberosum L.) crops. Field experiments were therefore conducted in various regions of Australia to determine if Cd uptake by potatoes could be minimised by changes in either phosphorus (P), potassium (K) or zinc (Zn) fertilizer management.Changing the chemical form in which either P fertilizer (monoammonium phosphate, diammonium phosphate, single superphosphate and reactive rock phosphate) or K fertilizer (potassium chloride and potassium sulfate) were added to crops had little influence on tuber Cd concentrations. Fertilizer Cd concentrations also had little influence on tuber Cd concentrations, suggesting that residual Cd in the soil was a major contributor to Cd uptake by the crops on these soils.Addition of Zn at planting (up to 100 kg Zn ha^–1) significantly reduced tuber Cd concentrations at four of the five sites studied. However, the largest variation was between sites rather than between treatments, with site mean tuber Cd concentrations varying tenfold (from 0.018 to 0.177 mg Cd kg^–1 fresh weight). Factors associated with irrigation water quality at the sites, in particular the chloride concentration, appeared to dominate any effects of changing fertilizer type or Cd concentration.     

入世后高浓度磷肥中镉的问题

入世后 ,TBT协议所形成的技术贸易壁垒将影响我国磷肥进出口贸易 ,讨论高浓度磷肥中放射性元素镉的分布、除去方法 ;针对磷肥中潜在镉的污染问题 ,建议利用 TBT协议建立必要的技术壁垒。     

Assessment of fertilizer P residues in a calcareous vertisol

The amounts of available P in a Typic Pellustert containing different levels of residual fertilizer P were assessed in a field experiment and chemically with cation-anion-exchange resin, using: (i) P desorbed after 1 extraction, (ii) cumulative P from 8 extractions [Resin8-P] and (iii) the asymptote of the extraction curve. P exchangeable to³²P, Olsen-P and P extracted by dilute salt solution (0.03M KCl) were also measured. P available to sorghum in 1989 was strongly influenced by fertilizer P applied in 1988, but not by P applied in 1987. Olsen-P and Resin8-P both reflected well the effects of residual P on yield and P uptake and could therefore be used to predict available residual P. The amounts of Resin8-P were much larger than Olsen-P, so it was easier to observe the differences between soil treatments, but Olsen-P gave the better correlations with grain yield and P uptake.Multiple regressions of crop yield or P uptake with amounts of P applied in 1987 and 1988 gave the best correlations, without the need for practical work. Thus, the development of an appropriate model based on records of P fertilization is seen as the most effective way to predict availability of residual P. Assessments related to the P intensity and desorption rate using resin were not able to improve predictions of available P, indicating that within one soil the quantity of residual P is most important, but for comparisons between soils, account will need to be taken of differences in soil characteristics.Approved for publication as Journal Article No. 1309 of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Agronomical evaluation of phosphate fertilizer as a nutrient source of phosphorus for crops: Isotopic procedure

The agronomic effectiveness of P fertilizers, as sources of phosphorus for crops, was evaluated using the quantities, P_f, of phosphorus taken up byLolium perenne grown on 14 soils during greenhouse experiments in pot cultures. The P_f quantities were determined using³²P-labelled fertilizers. Data were analysed using a new concept: the Isotopic Relative Agronomic Effectiveness (IRAE). The IRAE value was defined as the ratio of the P_f quantity, taken up by a crop, of a tested fertilizer over the P_f quantity, taken up by a crop, of a fertilizer used as standard. In our experiments diammonium phosphate (DAP) was used as standard P fertilizer and two rock phosphates, the North Carolina rock phosphate (NCPR) and a calcium-iron-aluminium phosphate (Phospal), were tested. As a linear relationship between P_f(NCPR) quantities and P_f(DAP) quantities was obtained, with r² = 0.95, when the application rates increased from 15 mgP (kg soil)^–1 to 200 mgP (kg soil)^–1, it is conciuded that IRAE values for a given fertilizer, other than the standard fertilizer, could be determined with a single rate of application. As regards soil pH in the range 4.7 to 8.2 the IRAE_NCPR is related to soil pH by a curvilinear relationship: log IRAE_NCPR = –(0.44) pH + 4.05 with r² = 0.89. The average of IRAE_phospal values was 0.15 with a standard error = 7% irrespective of soil pH. Then a logarithmic relationship was obtained between IRAE values of the two tested fertilizers and their water P-solubility determined at the soil pH where they were applied.     

不同添加剂对铅锌矿渣污染土壤中重金属有效态含量的影响

用不同土壤添加剂:石灰、钙镁磷肥、粉煤灰及磷酸氢二铵,以逐步增加的改良剂施用于土法练锌废渣混合土壤,研究不同改良剂处理对土壤中重金属有效态的影响,并分析了其变化趋势。结果表明,土壤添加剂施用量增多,土壤中重金属有效态随之降低;在一定添加剂施用区间内,重金属有效态并不随添加剂施用量的增多而降低,而是呈现一种稳定状态;同时,在这个区间内,土壤添加剂的处理效果大致为磷酸氢二铵钙镁磷肥石灰粉煤灰。     

Phase mixture modeling of the grain size dependence of Young’s modulus and thermal conductivity of alumina and zirconia ceramics

The grain size dependence of Young’s modulus and thermal conductivity of alumina and zirconia ceramics is predicted via phase mixture modeling, using both analytical and numerical approaches. Using typical values for the thickness and properties of the grain boundaries, the equivalent volume fraction of “grain boundary phase” is calculated for a given grain shape. Based on this volume fraction estimate and a rough estimate of the grain boundary properties, the effective properties of the polycrystalline materials are calculated and compared in terms of volume-equivalent sphere diameters. For grains of cubic and tetrakaidecahedral shape excellent agreement is found between numerical calculations and analytical predictions based on the lower Hashin-Shtrikman bound. The grain size dependence is extremely weak for Young’s modulus, but can be more significant for thermal conductivity, especially when the intrinsic conductivity of the material is high. The predictions are compared to literature data.     

Influence of soil organic carbon on the interpretation of soil test P for wheat grown on alkaline soils

Organic carbon is known to alter crop response to applied phosphorus (P) but that fact has not been incorporated in soil test interpretations. To achieve this objective, field experiments with wheat were conducted for four years on alkaline soils of Punjab, India. The experimental soils ranged from loamy sand to loam in texture, 7.4 to 9.6 in pH, 0.16 to 0.75% in organic carbon (OC) and 2 to 40 mg Olsen extractable P kg^–1 soil. Response of wheat to fertilizer phosphorus application was related to the combined effect of Olsen P and soil OC content. At a given Olsen P level, wheat yield was a function of soil OC content. Multiple regression analysis of the data showed that OC content <0.2% did not affect yield significantly. At values >0.6%, OC along with Olsen P accounted for 97% of the variation in yield and there was no response to applied fertilizer P. Yield isoquants for 4 and 5 tons grains ha^–1 showed that for a given Olsen P level, as OC content increased the amount of fertilizer P required to achieve a yield target decreased. It was shown that OC may be used to approximate the contribution of organic P mineralization to plant available soil P during a growing season. The reliability of fertilizer recommendations based on Olsen P may be improved on some alkaline soils by consideration of soil OC content.     

Intercropping of Wheat and Pea as Influenced by Nitrogen Fertilization

The effect of sole and intercropping of field pea (Pisum sativum L.) and spring wheat (Triticum aestivum L.) on crop yield, fertilizer and soil nitrogen (N) use was tested on a sandy loam soil at three levels of urea fertilizer N (0, 4 and 8 g N m⁻²) applied at sowing. The ¹⁵ N enrichment and natural abundance techniques were used to determine N accumulation in the crops from the soil, fertilizer and symbiotic N₂ fixation. Intercrops of pea and wheat showed maximum productivity without the supply of N fertilizer. Intercropping increased total dry matter (DM) and N yield, grain DM and N yield, grain N concentration, the proportion of N derived from symbiotic N₂ fixation, and soil N accumulation. With increasing fertilizer N supply, intercropped and sole cropped wheat responded with increased yield, grain N yield and soil N accumulation, whereas the opposite was the case for pea. Fertilizer N enhanced the competitive ability of intercropped wheat recovering up to 90% of the total intercrop fertilizer N acquisition and decreased the proportion of pea in the intercrop, but without influencing the total intercrop grain yield. As a consequence, Land Equivalent Ratios calculated on basis of total DM production decreased from a maximum of 1.34 to as low as 0.85 with increased fertilizer N supply. The study suggests that pea–wheat intercropping is a cropping strategy that use N sources efficiently due to its spatial self-regulating dynamics where pea improve its interspecific competitive ability in areas with lower soil N levels, and vice versa for wheat, paving way for future option to reduce N inputs and negative environmental impacts of agricultural crop production.     

A simple model for estimating the nitrogen fertilizer requirement of a cereal crop

A static model that predicts the nitrogen (N) fertilizer requirement of grain sorghum or wheat crops is described. Inputs required by the model are soil nitrate-N (kg ha^–1) in the profile at sowing, total N (%) in the plough layer, available water in the profile at sowing (mm) plus rainfall during the growing season (mm). Output includes fertilizer N required for both maximum yield and optimum economic yield.The model was tested by using published field data from Nebraska and Kansas (U.S.A.), South Australia and Northern Territory (Australia), and Saskatchewan (Canada). The model was accurate when no fertilizer N was required, and when large amounts were required, but quantitative prediction of moderate requirements was only fair. Predictions for grain sorghum were better than for winter wheat, probably because total water use was a better predictor of yield potential for grain sorghum than for winter wheat. Further refinement for specific environments should make the model practical for dryland cereal crops.     

A comparison of seven soil P tests for plant species with different external P requirements grown on soils containing rock phosphate and superphosphate residues

Seven soil tests for phosphate (P) (Bray 1, Bray 2, Truog, ammonium oxalate, Colwell, iron oxide-strip (Pi) and resin-strip soil tests) were evaluated for predicting the yield of plant species which have very different external P requirements. Two acid, sandy soils that had been fertilized six years previously with superphosphate and three rock phosphates were used. A glasshouse pot experiment with lettuce, wheat and maize was used to calibrate the soil tests.For some soil P tests, different calibrations relating yield to soil P test values were required for each plant species, P fertilizer and soil combination. The Bray 2 and Truog soil P tests were the worst predictors of yield for both soils and all plant species. The Pi and ammonium oxalate tests were the most predictive tests for one soil when data for all fertilizers were considered. The Bray 1 and Colwell soil P tests were the most predictive for the other soil. The resin-strip P test was poorly predictive of yield of lettuce and wheat for both the soils. The accuracy in prediction of yield on the basis of P test value decreased in the sequence maize > wheat > lettuce. This rank is opposite to the increasing external P requirements of these species.     

The role of manganese and nitrogen nutrition in the susceptibility of wheat plants to take-all in Western Australia

Five field experiments are described which measured the effect of take-all on grain yield of wheat when 5 levels of manganese fertilizer were applied in a factorial combination with 5 different types of nitrogen fertilizer.Ammonium nitrogen fertilizer, either as ammonium sulphate or ammonium chloride, lowered the severity of take-all. By contrast, sodium nitrate had no effect on the incidence and severity of take-all. Ammonium chloride and ammonium sulphate were equally effective at controlling take-all, suggesting that the chloride or sulphate ion had little or no effect on the disease.Manganese sulphate decreased take-all severity at two trial sites. Where manganese was deficient, an application of manganese lowered the severity of take-all, had no effect on the incidence and increased the dry matter and grain yields of the wheat plants. There were no beneficial effects of applied manganese if the wheat plants were adequately supplied with soil manganese.The results suggest that take-all is more severe where plants are deficient in either manganese or nitrogen. The work also suggests that manganese deficiency is not necessarily the reason why the wheat plants grown on the acid soils of south-west Western Australia are prone to take-all.