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  • 1
    ISSN: 1573-0867
    Keywords: 32P ; plant P uptake ; soil P taken up by plants ; soil-plant relationships ; soil test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A laboratory method and a laboratory index is proposed to estimate the phosphorus taken up by plants that is derived from fertilizers (Pdff). Pdff values were measured using greenhouse experiments and32P labelling technics. The laboratory index estimates the proportion of PO4-ions derived from the fertilizer in the soil solution and is measured by means of an isotopic exchange of32PO4-ion procedure. This indicator was named JCF. Two typical soil-fertilizer conditions were studied. One concerned measurement of Pdff and JCF values for freshly-applied phosphorus as diammonium phosphate (DAP) at levels of 15, 30, 45, 60 and 90 mg P kg−1 soil. The other concerned measures of Pdff and JCF values for two types of P residues previously applied in soils as concentrated superphosphate (CSP) or Gafsa rock phosphate (GRP) applied at 0 and 43.7 kg.ha−1 each year over a 15 yr period. For freshly-applied DAP a linear relationship between Pdff and JCF values was obtained over the range of 0 to 90 mg P (kg soil)−1 levels of application: JCF = 1.16 Pdff + 1.78, (r 2 = 0.98). For the P residues, JCF and Pdff values were not significantly different for a given residual treatment. However JCF and Pdff pair data for CSP treatments (56.0, 65.9) were about tenfold superior to those for GRP treatments (5.3, 4.6)). Consequently the nearly 1:1 ratio between JCF and Pdff values that was obtained for the two different soil-fertilizer conditions suggests that the proposed laboratory method can be used to predict availability of P fertilizers to plants. Thus it deserves to be considered in helping to estimate P fertilizer applications.
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  • 2
    ISSN: 1573-0867
    Keywords: Ammonium sulphate ; urea ; sub-surface placement ; broadcast application ; N yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of different methods of N fertilizer application-sub-surface placement (SS) and broadcast application (BC) as a single basal dose of 40 kg N ha−1 of urea (U) and ammonium sulphate (AS)-on fresh weight (FW) and acetylene reduction activity (ARA) ofAzolla pinnata (Bangkok) and yield of rice was studied for consecutive three seasons. The FW, ARA and N yield ofAzolla were significantly superior with SS placement than with BC application. Of the two N sources, AS was superior to U in recording higher FW, ARA and N yield of Azolla irrespective of methods of N application. Crop yield and crop N uptake were higher with SS application alone and in combination with Azolla as compared to that of surface application of N fertilizers. The combined use of AS and Azolla recorded significantly higher crop yield and crop N uptake than that of U combined with Azolla, irrespective of methods of application.
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  • 3
    ISSN: 1573-0867
    Keywords: Acid soil ; calcareous soil ; nitrogen fertilization ; ammonia volatilization ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonia loss from surface-applied urea occurs because urea hydrolysis increases the pH of the placement site microenvironment. Addition of Ca-salts with urea will control or reduce the microsite pH, thus reducing NH3 losses. The degree of Ca-saturation of the cation exchange sites may influence the ratio of calcium:urea required to control ammonia loss. A laboratory study was conducted to determine if adsorbed Ca or CaCO3 additions (acid soils only) had a measureable impact on Ca control of NH3 loss from surface applied urea at various Ca:urea ratios. With urea alone applied to the soil surface varying the adsorbed Ca content of the treatment soil did not influence NH3 loss. The addition of CaCl2 with urea on the same pretreated soils generally resulted in NH3 losses reflecting the initial pH of the soil. The Ca-saturated acid soils and those acid soils receiving CaCO3 had higher NH3 losses than untreated soils in the presence of urea with soluble CaCl2. It was noted that increasing the calcium:urea ratios progressively depressed the NH3 loss from all soils. Increasing the percent Na-saturation of the calcareous Harkey soil to 25 and 50% (ESP) reduced Ca control of NH3 loss due to Ca being exchanged for Na on the cation exchange sites. Inclusion of CaCl2 with the urea mixture on the surface of the pretreated acid soils resulted in stepwise differences in NH3 loss concuring with the increases in pretreatment soil pH values (differing exchangeable Ca content). Other parameters that influence the amount of NH3 loss, such as acidic buffer capacity and CEC, appeared more important than anticipated for control of NH3 loss with the calcium:urea mixture. On Ca enriched soils the calcium:urea mixture was only slightly less effective in its ability to control NH3 losses than on untreated soils.
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  • 4
    ISSN: 1573-0867
    Keywords: Urea ; urea supergranule ; phenyl phosphorodiamidate ; 15N balance ; N losses ; pH ; acid sulfate soil ; ammonium phosphate sulfate ; Oryza sativa L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was conducted on an acid sulfate soil in Thailand to determine the effect of N fertilization practices on the fate of fertilizer-N and yield of lowland rice (Oryza sativa L.). A delayed broadcast application of ammonium phosphate sulfate (16-20-0) or urea was compared with basal incorporation of urea, deep placement of urea as urea supergranules (USG), and amendment of urea with a urease inhibitor. Deep placement of urea as USG significantly reduced floodwater urea- and ammoniacal-N concentrations following N application but did not reduce N loss, as determined from an15N balance, in this experiment where runoff loss was prevented. The urease inhibitor, phenyl phosphorodiamidate (PPD), had little effect on floodwater urea- and ammoniacal-N, and it did not reduce N loss. The floodwater pH never exceeded 4.5 in the 7 days following the first N applications, and application of 16-20-0 reduced floodwater pH by 0.1 to 0.3 units below the no-N control. The low floodwater pH indicated that ammonia volatilization was unimportant for all the N fertilization practices. Floodwater ammoniacal-N concentrations following application of urea or 16-20-0 were greater on this Sulfic Tropaquept than on an Andaqueptic Haplaquoll with near neutral pH and alkaline floodwater. The prolonged, high floodwater N concentrations on this Sulfic Tropaquept suggested that runoff loss of applied N might be a potentially serious problem when heavy rainfall or poor water control follow N fertilization. The unaccounted-for15N in the15N balances, which presumably represented gaseous N losses, ranged from 20 to 26% of the applied N and was unaffected by urea fertilization practice. Grain yield and N uptake were significantly increased with applied N, but grain yield was not significantly affected by urea fertilization practice. Yield was significantly lower (P = 0.05) for 16-20-0 than for urea; however, this difference in yield might be due to later application of P and hence delayed availability of P in the 16-20-0 treatment.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 15 (1988), S. 89-99 
    ISSN: 1573-0867
    Keywords: solubility ; fertilizer solutions ; phosphate ; urea ; ammonia ; potassium ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Data from four solubility studies for liquid fertilizer solutions containing three or more plant nutrients are presented on equilateral triangles. Isoconcentration contour lines indicate the maximum solubility of the nutrients as the sum of the plant food components, i.e., total plant nutrient = %N + %P2O5 + %K2O. One study was based on an ammoniated phosphoric acid (80% polyphosphate level)-urea-potassium chloride-water system. The base solution was a nominal 11-37-0 grade, with one-fifth of the total phosphate derived from wet-process phosphoric acid and the remainder from electric-furnace acid. Two of the studies were with nonchloride sources of potash, and the fourth study was with ammonium sulfate as a source of sulfur and supplemental nitrogen. All solubility data were measured at 0°C. However, estimates of solubility at other temperatures can be made by proper use of temperature-solubility factors. Also given are areas on the figures indicating precipitating salts, as determined by petrographic examinations.
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  • 6
    ISSN: 1573-0867
    Keywords: manpower requirements ; public policy ; training ; fertilizer sector ; sub-Saharan Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract 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.
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  • 7
    ISSN: 1573-0867
    Keywords: rice ; urea supergranules ; sulfur-coated urea ; placement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Conventional as well as modified nitrogen sources and application methods were evaluated under rainfed lowland conditions in heavy clay soils of Bihar, India for 4 years. Modified nitrogen sources, viz. sulfur-coated urea (SCU) and urea super-granules (USG) were tested against prilled urea (PU) under four levels of N (0, 29, 58 and 87 kg N/ha) in the wet season. A high yielding nonphotoperiod sensitive, long duration variety ‘Pankaj’ was grown in all the four years. Point placement of USG and basal incorporation of SCU resulted in significantly higher panicle numbers per square meter, 100 grain weight and grain yield at all the levels of N tested. The unfilled grain percentage was lower in USG and SCU treatments. Regression analysis using a multifertilizer response model (MRM) showed that rice responded significantly to PU in three years out of four years, to SCU in four years and USG in three years. Economic analysis viz. input and output analysis based on the price of fertilizer (1 kg N as PU at $0.5; USG and SCU costing 10% more than PU), rough rice (ranging from 18.0 to 20.0 $ per ton) and labour wages at 1.0 $ per man day unit, also showed that USG and SCU are more input efficient than PU.
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  • 8
    ISSN: 1573-0867
    Keywords: corn ; soybean ; wheat ; maximum yield ; optimum yield ; Bray P1 ; exchangeable K
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Data from 32 years of a rotation-fertility experiment were analyzed to determine the average P and K application rates required for maximum yield and for optimum yield. A four-year rotation of corn, soybean, wheat, hay was used for the first 10 years and then changed to corn-1, soybean, wheat, corn-2. Rates of P application per 4-year rotation ranged from 0 to 196 kg ha−1 and for K from 0 to 558 kg ha−1. Multiple regression equations were fitted to the mean yields per 4-year rotation for the response of each crop to P and K applications. The range in P application rates in kg of P per 4-year rotation required to get maximum yields of corn was 118 to 172, for soybeans was 134 to 150, and for wheat was 116 to 138. The range in K application rates in kg K per 4-year rotation to get maximum yields of corn was 378 to 411, for soybeans was 324 and 476, and for wheat was 11 to 323. For rates of application where P and K added exceeded crop removals, soil test P and K increased linearly with the cumulative positive balance of P and K. Where crop removal exceeded application rate, no relation was found between crop removal and soil test.
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  • 9
    ISSN: 1573-0867
    Keywords: Exchangeable calcium ; incubation ; level of phosphate rock application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of the particle size of North Carolina phosphate rock on its dissolution in soil was investigated in the laboratory using four size fractions (150–250, 106–125, 45–53 and 〈 38µm) and two levels of application. Dissolution as measured by soil-exchangeable Ca increased to a minor extent with both decreasing particle size and incubation period. For a PR application of 400µg P/soil the percentage dissolution ranged with decreasing particle size from 13 to 18% and 14 to 20% of applied P for 7 and 35 days incubation periods respectively. The highest percentage dissolution occurred for the smallest particle size. The percentage dissolution was much lower (6–7% and 7–8% of applied P for 7- and 35-day incubation respectively) for the higher application level of 1600µg P/g soil although the absolute amounts of dissolution were larger. Amounts of bicarbonate-soluble p in the soil also increased with decreasing particle size and were about 3–4% and 1% of applied P for 400 and 1600µg P/g levels of application respectively for the 35-day incubation.
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  • 10
    ISSN: 1573-0867
    Keywords: Citrus sinensis ; leaf analysis ; nitrogen uptake ; Phosphorus Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A long-term experiment was carried out in a mature orange grove comparing broadcasting versus continuous application of nitrogen at three rates (80, 160, 280 kg ha−1), 22 kg P ha−1 and 126 kg K ha−1 annually. The trees were irrigated with minispriklers wetting 70% of the soil area. The level of NO3-N in the leaves varied according to the rate of N application. Leaf K and P content were not affected by fertilization. High N applications caused excess N in the soil solution. The rate of N application did not affect orange yield, fruit size or quality. Fertigation at 160 kg N ha−1 caused higher yields than when the same amount of fertilizer was broadcast. At the high application rate, no differences between modes of application were found.
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