Economic control of fertilizer in highly productive pastoral systems. I. A theoretical framework for the fertilization problem

A hypothetical model, based on plant physiology and termed ‘Mitscherlich-Liebig’, is proposed as a general solution to the problem of estimating an optimum fertilizer rate from results in a field trial; in combining the ideas of Liebig and Mitscherlich the model involves the following proposals:

1. Diminishing returns in a smooth exponential relation between input and output culminating in a yield-plateau.
2. The difference between this plateau and the ideal asymptotic maximum is the result of an unavoidable osmotic depression caused by salts in the root zone.
3. Liebigian nonsubstitution of one essential elemental nutrient by another.
4. Quantitative equivalence in output from essential inputs when each is expressed in terms of a physiologically standardized amount defined as a Baule unit.
5. Pooling response data according to a relative yield theory and the Baule unit concept, rather than grouping data according to a soil type theory and the concept of a response curve unique for the element concerned.

In addition to certain other biometrical implications, these concepts provide an explicit method for estimating the composition of a balanced fertilizer mixture, whereby a profit maximising calculation may be applied through the ratio: cost of applied fertilizer/price of harvested yield. This approach to the problem permits a formulation of fertilizer advice theoretically sound in plant physiology as well as economics.     

Changing fertilizer practices

Traditional fertilizer practices using mostly single (ordinary) superphosphate applied to pastures on sandy-surfaced soils in the coastal areas of south-western Australia has contributed greatly to the eutrophication of waterbodies of the region. To reduce eutrophication, it is necessary to modify traditional fertilizer practices, involving the accurate definition of nutrient requirements for specific situations, and the evaluation of fertilizer strategy options to achieve optimal levels of yield. A model was developed to integrate available information on phosphorus, sulphur and potassium responses in pastures, and to estimate optimum fertilizer application requirements. The model uses a Mitscherlich function to describe pasture responses to applied fertilizer. Use of the model to estimate optimum fertilizer application rates also allows evaluation of the cost to agricultural production of reducing fertilizer application rates based on environmental rather than on agricultural productivity objectives.     

Residual soil P values for permanent pastures on reclaimed scrubland from Galicia (NW Spain).

In the reclamation of scrublands of Galicia in NW Spain, fertilization is necessary to establish pastures. The area is particularly responsive to P fertilizer. In order to maximize the efficiency of use of fertilizer in planning fertilization programs, it is necessary to take into consideration the residual as well as the freshly added P.Phosphate fertilization experiments were conducted in four sites in Galicia having a range in soil properties. The treatment design allowed estimation of residual P one year after fertilization in terms of freshly applied P equivalents.Four non-linear models were fitted to the data from the experiments after it was determined that residual soil P one year after fertilization was proportional to the amount of P applied. The estimated proportion of P remaining one year after application appeared to be independent of the model chosen. The Mitscherlich performed best from the standpoint of average residual mean squares, total rank, residual behavior after the fit and ease of fit.The percent of fresh fertilizer equivalent estimated one year after addition ranged from 60–90 for soils formed from granite, 30–60 for soils from slates, and 30 for soils over schist and gabbros.     

Economic control of fertiliser in highly productive pastoral systems. V. Extending advice through the Mitscherlich-Liebig model

A general solution is proposed to the problem of extending economic fertilizer advice over a highly productive pastoral area. The scheme implies a subdivision of the area through objective information obtained from widely dispersed, long-term, 3 level field trials; within sub-areas advice appropriate to a particular farm, or part thereof, is specified by incorporating more or less subjective estimates concerning level of output from the current input of fertilizer and carry-over of fertility in the field from one year to the next. The mathematical model used to facilitate an economic evaluation has been termed ML because it combines two cardinal principles: Mitscherlich's Law of Diminishing Returns and Liebig's Law of the Minimum, and is thus in accord with both economic and physiological theory. The model has been used to assess the effectiveness of chemical soil testing as a means of estimating carryover of fertility and to study the sensitivity of economic advice to error in the vital ratio: cost of input/selling price of output. The concept of a common response curve for essential elements has been developed as a basis for calculating the composition of a complete physiologically balanced fertilizer.The articles I–IV appeared inFertilizer Research 4:4 (1984)     

Relationship between electroultrafiltration (EUF) extractable nitrogen,grain yield,and optimum nitrogen fertilizer rates for winter wheat

The objective of the investigation was to examine whether there exist relationships between the optimum nitrogen fertilizer rate for winter wheat and soil nitrogen fractions extracted by electroultrafiltration (EUF) from autumn samples of the upper soil layer (0–30 cm). Optimum nitrogen fertilizer rates were derived from grain yield curves of field trials carried out with increasing nitrogen fertilizer rates on 19 different sites in 1985/86 and 1986/87. Most soils were luvisols derived from loess, two soils were brown earths and one a pararendzina. Total Nitrogen fertilizer rates were 0, 40, 80, and 120 kg N/ha applied twice before ear emergence. The final nitrogen rate at ear emergence was the same for all treatments, namely 60 kg N/ha.Optimum nitrogen fertilizer rates were derived from the grain yield curve fitted to a modified Mitscherlich equation. The optimum nitrogen fertilizer rates were correlated with the nitrogen fractions extracted by EUF. The regression equation thus obtained showed that NO ₃ ^- , the organic N fraction (EUF Norg), and the EUF Norg-quotient each had a highly significant impact on the optimum nitrogen fertilizer rate. The higher the amounts of EUF-N extracted the lower the optimum nitrogen rate. Substituting the EUF Norg-fraction for total nitrogen concentration in the upper soil layer gave a poorer relationship between the optimum nitrogen fertilizer rate and the soil data. In absolute terms the EUF Norg-fraction had by far the greatest impact on calculating the optimum nitrogen fertilizer rate. The investigation shows that the EUF method is a suitable technique for the determination of available soil nitrogen from which optimum nitrogen fertilizer rates can be derived for winter wheat cultivated under soil and climatic conditions typical for cereal growing areas in central Europe.     

Yield response of lentil to directly applied and residual phosphorus in a Mediterranean environment

The response of lentil grown under rainfed conditions to directly applied and residual phosphorus (P) was described by a modified Mitscherlich equation, accounting for the effects of rainfall on (1) potential yield, and (2) the availability of soil-P to the crop. The response of lentil yield to directly applied and residual P was studied in two-course cereal–lentil rotational trials under rainfed conditions in a Mediterranean-type environment. Cereal crops were grown at different P application rates during 4 growing seasons at 3 sites, representing different rainfall zones in northwest Syria. Lentil (Lens culinaris Med.) was grown during 4 seasons at the same sites, each lentil crop following a cereal crop. In 3 out of 4 lentil-growing seasons, additional P was applied to lentil in subplots to compare the residual and direct effects of P application. The initial contents of extractable soil-P (P-Olsen) were low at all sites, in the range of 2–5 ppm P. Under the conditions of the experiments, lentil appeared to benefit slightly more from P applied to the preceding wheat crop (residual P) than from directly applied P. It is shown that the modified Mitscherlich equation could be used as a basis for P fertilizer recommendations for rainfed farming. As for lentil, it was concluded that a single application of P to the wheat crop in a wheat/lentil rotation could reduce the cost of lentil production, without reducing lentil yield.     

Incorporating the effects of plant density into fertilizer response models

Equations describing the yield response to a limiting nutrient (the Mitscherlich equation) and the effect of plant density on yield are combined into a single model for the yield response surface as a function of both plant density and rate of application of a nutrient. As an example, the model was applied to data from an experiment studying the response of soybeans to phosphorus in which between-plot variation in plant density was large. The model gave a good fit and thus considerably improved the definition of the phosphorus response.     

Ability of a dynamic model of phosphorus to account for observed patterns of response in a series of phosphate fertilizer trials on pasture

A national series of rates × forms of phosphate fertilizer trials has provided a large amount of data on patterns of response of pasture production and soil P tests to forms, rates and frequencies of P fertilizer application over time. A simple mechanistic model of P in pastoral systems has been developed in an attempt to account for the observed patterns. The model considers active P in the soil to be in one of two compartments: undissolved fertilizer P (P_F) and a pool of labile, plant-available P (P_A). P dissolving from P_F enters P_A, and P is lost from P_A by immobilisation in the soil and by net removal above ground through non-recycled uptake by plants. Both these transfers are taken to follow first order kinetics, with rate constants designated K₁ and K₂ respectively. Pasture dry matter (DM) production in any year is related to the mid-year value of P_A by the diminishing-returns Mitscherlich equation, with nil pasture yield being associated with nil P_A.Data from different sites with the same design were combined to give generalised response patterns with which to assess the model. Only the control treatment and treatments receiving triple superphosphate (TSP) and Sechura phosphate rock (SPR) were considered. With a value for K₁ corresponding to almost immediate dissolution, the model accounted well for the Olsen soil P test patterns from TSP when K₂ corresponded to an annual loss of 16.3% of P in P_A and a factor of 10 was used to convert Olsen P to kg P/ha in P_A. Pasture DM yield response curves to rates of TSP in individual years were well accounted for when the mid-year value of P_A required for 90% relative yield was taken as 130 kg P/ha. The model also accounted well for the difference between response patterns to annual and triennial TSP applications for both soil P tests and DM production. The declines in soil P tests and DM production which occurred in nil P controls were less than model predictions: this could be due to unfertilised pasture making more use of P from greater soil depth or less available forms.Olsen P tests with the higher rates of SPR were always lower than model predictions using a value for K₁ derived from chemical measurement of SPR dissolution rates in the trials. However, DM yields from SPR were generally close to model predictions. These divergent results support independent data suggesting that available soil P from reactive phosphate rocks (RPRs) is underestimated by the Olsen P test.The relative success of this simple compartmental model in accounting for generalised response patterns in such a large body of data suggests that it could be a useful starting point for a dynamic P fertilizer recommendation model.     

一次基施缓释肥对小麦产量和效益的影响

通过不同缓释肥与普通肥料进行肥效试验,结果表明:一次性施用缓释肥比普通复合肥增产效果明显,小麦增产幅度在2.6%~17.1%;提高了小麦有效穗数和穗粒数;经济效益增幅在598.6~2 683.8元/hm2;缓释肥施用量减少15%的施肥条件下,小麦保持稳产。     

Manpower requirements for the fertilizer sector in sub-Saharan Africa

The manpower requirements are estimated for the fertilizer sector (production, marketing, and use) in sub-Saharan Africa from 1982/83 to 2002/3. The additional technical manpower requirements in sub-Saharan Africa over a 20-year period are about 15,917 persons for fertilizer production, 7959 for fertilizer marketing and 7958 for fertilizer use. It is estimated that, on the average, an additional 1592 persons will be required annually for the fertilizer sector. There is thus a need to establish —through both national and international organizations— appropriate fertilizer training facilities. This will relax serious manpower constraints in fertilizer sector development and thus will accelerate the contribution of fertilizer to economic growth in sub-Saharan Africa.     

经济危机背景下中国磷肥工业面临的问题与机遇

中国磷肥工业面临的处境从来没有今天这样尴尬,它既要替政府担负农业安全的重任,又要直接去面对市场。2008年的宏观调控和经济危机的双重冲击,使中国磷肥工业遭受巨额损失。其全年经济总量仅2400亿元,单就高价硫磺给行业带来的损失就超过200亿元。全行业过去10多年的积累毁于一旦,进入成本与市场严重倒挂、产能严重过剩、对国外市场过度依赖的泥潭。如今,全球性经济危机尚未见底,中国磷肥工业如何走出泥潭,是业界普遍关注的话题。本文试图通过历史的回顾,挖掘行业存在的问题,探索中国磷肥工业新生的希望。     

Residual effects of phosphate fertilizers in relation to phosphate sorptivities of 27 soils

Three different parameters of the long term effects of phosphate fertilizers on perennial clover-based pastures were measured over 3–4 years in 27 experiments on acidic soils in an elevated region of eastern Australia. Recovery of fertilizer P was the difference between herbage P uptake in the presence of fertilizer and uptake in its absence, expressed as a % of the amount of P applied in the first year. Residual value was the size of the response to fertilizer P, applied in the first year, expressed as a percentage of the response to freshly applied P in the second and third years. Effectiveness was the product of the values of the Mitscherlich curvature and response parameters for each response curve, and residual effectiveness was relative to initial effectiveness. Soils varied widely in their P sorptivities, and represented Alfisols, Entisols, and Ultisols of basaltic, granitic and sedimentary origin. Mean P recoveries of 29% in the first year and 49% over 3 years, residual values of 84% in the second year and 60% in the third, and residual effectiveness of 77% in the second year and 47% in the third were high by most standards. Increasing P sorptivity tended to increase fertilizer effectiveness in the first year and residual value in the second year, but it depressed P recovery in the first year and residual effectiveness in later years. The long term effect of increasing P sorptivity on cumulative P recoveries tended to be negative at low to medium rates of fertilizer application and positive at high rates of application. There was a much smaller decline in residual values and effectiveness over the 3 or 4 years than there was in P recovery, and this was attributed to the beneficial effects of P on soil N fertility, via clover N fixation, and the subsequent growth of grasses in the phosphated treatments.     

Calibration of available P in soils from derived savannah zone of western Nigeria

Extractants for determining soil available P are useful in fertilizer recommendations when calibrated with actual yield responses. The relationships between relative (or percent) yield and soil P test levels can be described using various mathematical models, and the relevant critical P levels estimated.Critical P values for 60 cultivated savannah surface soils estimated in a greenhouse study and for 20 soils in 20 field observations varied with extractants. Most of the soils studied were deficient in P with 4–10 mg kg^–1 available P range. Calibration of P in soil using the Cate and Nelson's analysis of variance method, Mitscherlich and quadratic equations compared favourably. The advantages of the Cate and Nelson's procedure were discussed.     

Fertilizer adoption by small-scale farmers in Nakuru District,Kenya

This study identifies the socio-economic factors responsible for fertilizer adoption in Nakuru District, Kenya. Data for the study were obtained from a cross section of the farmers by using a multi-stage random sampling technique to purposively select both adopters and non-adopters of fertilizers. The probit model was employed to analyse the data via the maximum likelihood estimation technique. In addition, by making use of changes in stimulus level due to changes in socioeconomic variables, the effect of different policy options on fertilizer adoption was explored.The results of the study indicate that fertilizer adoption in the area of study is more sensitive to sociological and institutional factors than to economic factors such as labour and credit availabilities. Specifically, it is recommended among others that efforts be made to encourage farmers in the area to join cooperative societies. Also, frequency of extension visitation to the farmers should be increased for wide spread fertilizer adoption in particular and for the adoption of other new appropriate technologies by small-scale farmers in the area.     

味精厂废水生产麸酸有机复混肥在芥菜上的应用效果

采用田间试验方法研究了麸酸有机复混肥在芥菜上的应用效果。结果表明:与进口复合肥及单质化肥相比,施用麸酸有机复混肥的单季芥菜产量有所降低,但品质和经济效益增加。此外,施用麸酸有机复混肥有降低芥菜硝酸盐含量的趋势。综合产量、品质与效益分析,芥菜以1/2麸酸有机复混肥 1/2化肥配施模式最佳。     

Effects of fertilizer price on feasibility of efficiency improvement: Case study for an urea injector for lowland rice

Efficiency improving techniques, such as the introduction of a urea injector for lowland rice production, appear to lead to higher yields, lower fertilizer use and less environmental pollution at the same time. If farmers are free to decide on the amount of fertilizer they use, economic rationality leads to a choice between using the improved technique for saving fertilizer while obtaining the same yield, for increasing yield (at the same fertilizer rate) or for a mixed strategy (a slightly higher yield and a different fertilizer rate). The economic optimum fertilizer rate was calculated with a simple yield model for a low and a high fertilizer application efficiency to predict which strategy would be best for the farmer.Calculations for a standard data set for lowland rice show that the greatest benefit from an increase in application efficiency by urea deep placement instead of broadcast application can be expected when a marginal efficiency of about 9 kg rice per kg fertilizer N is used for determining the fertilizer rate. For a marginal efficiency of less than 6, savings on fertilizer are the main benefit of efficiency improvement; for higher marginal efficiencies yield increases become the main component of total benefit; for marginal efficiencies above 9, fertilizer use will increase when a more efficient technique is used, but increased yields compensate for their costs. In the four countries where a manually operated pneumatic urea injector was tested (Togo, Bangladesh, Indonesia and Ivory Coast) the price ratio of rice and fertilizer N ranged from 1.1 to 2.5. Even when a risk-avoidance multiplier of 2 is used, we may conclude that fertilizer prices were too low relative to rice to make optimum use of the existing techniques for efficiency improvement. An equation is derived for estimating the price ratio at which the probability of farmer acceptance of techniques for improving fertilizer use efficiency is highest.     

Orthogonal polynomial models to describe yield response of rice to nitrogen and phosphorus at different levels of soil fertility

Yield responses of rice (Oryza sativa L. cv JD1187)to variable rates and combinations of fertilizer nitrogen (N) and phosphorus(P), to available soil N and P, and to cation exchange capacity (CEC) wereexamined in 41 field trials. The trial sites were located in the rice-growingregion of Hebei Province, Northern China, covering a diversity of soilfertilitylevels. Relationships between crop yields, fertilizer rates and soil nutrientsupply were established using an orthogonal polynomial model. The optimumeconomic fertilizer rates at different levels of soil N and P supply wereestimated by using fertilizer-yield response functions and soil properties foraparticular site. A difference in trend coefficients, reflecting yield responseto fertilizer, was observed, which was mainly dependent on variance of soilfertility across 41 experimental sites under the relatively consistent climateand farming practice. The results of correlation analysis showed that there wasa positive correlation between trend coefficient T₀ and yieldwithoutfertilizer (Y₀) (r = 0.80**). Trend coefficientT₁, the major effect of N fertilizer on yield, showed negativerelationships with the quadratic transformation of alkali-hydrolysable N(N_s) and CEC (r = –0.60**). Trend coefficientT₂, the major effect of P fertilizer on yield, had negativerelationships with the logarithmically transformed data of soilNaHCO₃-extractable P (P_s) (r = –0.57**).Trend coefficients T₃, T₄ and T₅, representinglinear interaction of N and P, and quadratic trend of N and P, respectively,showed no significant correlation with soil fertility variables. Yieldresponsesto N and P fertilizers, optimum economic fertilizer rates and gross profit fromfertilization decreased with increase in available soil N and P, and CEC. Themodel was validated in 19 field trials. The results suggest that the modeldeveloped in this study can reasonably predict optimum economic fertilizerratesthrough routine soil tests in the rice production region. The model can also beextrapolated to other regions and include other variable factors, provided thatnew relationships between yield response to fertilizer and site variables areestablished and incorporated into the model.     

Spent mushroom compost as a nitrogen source for spring barley

Spent mushroom compost (SMC) contains a range of plant nutrients, including nitrogen (N), a large proportion of which originate from arable crops. Using SMC as an organic fertilizer for crops recycles these nutrients. Effective use of SMC in fertilizer regimes requires knowledge of the nitrogen fertilizer value (NFV) of the SMC, which is the amount of mineral fertilizer N required to give the same N yield, or marketable yield, as an application of SMC. The objectives of these experiments were to evaluate the effect of SMC on spring barley grain yield and quality and to determine its NFV. Experiments were carried out on two soils, light- and medium-textured, over 3 years (2008–2010). The experiments compared the yield response and N uptake of spring barley to fertilizer N with and without SMC. SMC application gave similar or higher grain yield and N uptake compared to fertilizer only treatments at corresponding fertilizer N rates. SMC had no significant (P > 0.05) effect on the economic optimum fertilizer N rate but the maximum yield was significantly (P < 0.05) higher where SMC was applied in two of the six experiments. Effects of SMC on grain quality were small. Results indicated that the NFV, expressed as a proportion of the total N applied in SMC, ranged from 0.05 to 0.29 kg kg^?1 N applied in SMC, with a mean of 0.15 kg kg^?1. It is concluded that SMC can contribute to the nitrogen nutrition of small grain cereal crops in high yield potential environments.     

A simple equation for calculating the residual effect of phosphorus fertilizers

A simple equation to calculate the residual effect of fertilizer phosphorus is derived from a model distinguishing only two soil phosphorus pools. With time intervals of one year the model calculates the phosphorus transfers between the pools, the uptake of phosphorus by the crop and the resulting pool sizes. Most input data required to operate the model can be obtained from ordinary one-season phosphorus fertilizer trials.For easily soluble phosphorus fertilizers the residual effect can also be calculated with a formula: Rt = (0.8 – R1)^t-1* R1 where Rt and R1 are the recovery fractions in year t and year 1, respectively. During the first five years after fertilizer application the residual effects, as calculated with the equation, are almost equal to those obtained with the model.     

水稻专用BB肥施用效果及运筹方法研究

根据江苏宿豫县土壤肥力状况及水稻需肥规律,研制推广水稻专用 ＢＢ肥（２０—８—１７）,在有代表性的土壤上进行试验。结果表明：施用水稻专用 ＢＢ肥,有利于稳定水稻群体,减轻病虫危害,增产效果显著,经济效益明显。运筹方法上以每公顷基施 ３７５ ｋｇ专用 ＢＢ肥加 ３７５ ｋｇ碳铵作返青肥,加 １５０ ｋｇ尿素作稳肥效果较好。