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  • 1
    Electronic Resource
    Electronic Resource
    Factors affecting N release of urea from reactive layer coated urea (1988)
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 273-284 
    Details
    ISSN: 1573-0867
    Keywords: Nitrogen ; coated fertilizer ; slow-release fertilizer ; RLCU
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An experimental fertilizer called reactive layer coated urea (RLCU) has been developed by coating urea with a mixture of diisocyanate and polyol in the presence of a catalyst. The hard, durable layer that is formed on the granule conveys slow-release character to the product. A series of soil incubation tests were conducted under simulated upland conditions for periods up to 56 days to study the effect of factors such as temperature, pH, soil moisture, and organic C additions on N release. The N release rate from RLCU was shown to be increased with increasing temperature and decreasing coating thickness. It was unaffected by the addition of lime to raise the pH or organic carbon sources to increase microbial activity. Although a slight effect of soil moisture was noted, it was not pronounced. Urea release tended to be in two stages — a constant diffusive stage in which, it is postulated, urea was still dissolving within the granule and diffusing to the soil at a constant rate and a slower logarithmic stage where the rate of release decreased with time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01051376
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  • 2
    Electronic Resource
    Electronic Resource
    Mineralization and nitrification of ureaform fertilizers (1988)
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 85-95 
    Details
    ISSN: 1573-0867
    Keywords: Dimethylenetriurea ; DMTU ; methylenediurea ; MDU ; ammonia volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In an attempt to produce N materials that exhibit some delayed-release character and yet make all the N available in one growing season, ureaform (UF) fertilizers were prepared using low amounts of paraformaldehyde (PFA) (6% to 15% PFA w/w). Mineralization and nitrification of the various water-soluble components of these UF materials were studied over a period of 35 days by use of15N and high pressure liquid chromatographic techniques. Only the dimethylenetriurea (DMTU) fraction and a fraction tentatively identified as triuret showed any slow-release character, whereas other water-soluble components mineralized rapidly. Less soluble fractions did not mineralize appreciably during the experiment. Due to their reduced solubility, these ureaforms were shown to be less susceptible to volatilization than was urea, and a 37% reduction in loss was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050459
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of efficiency of Mussoorie partially acidulated phosphate rock and single superphosphate in a shallow Alfisol of the Indian semiarid tropics (1993)
    Springer
    Nutrient cycling in agroecosystems 36 (1993), S. 29-33 
    Details
    ISSN: 1573-0867
    Keywords: Alfisol ; Bray 1-extractable P ; Mussoorie partially acidulated phosphate rock ; Olsenextractable P
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The agronomic effectiveness of a partially acidulated phosphate rock (PAPR) was measured in a field experiment with sorghum (Sorghum bicolor cv. CSH-6) in a shallow Alfisol at the ICRISAT farm, Patancheru (Hyderabad), India. The experiment compared PAPR with single superphosphate. The PAPR was made by acidulating an indigenous Indian phosphate rock (Mussoorie) with H2SO4 at 50% acidulation level. P response was evaluated at a single relatively high N rate (120 kg ha−1) with five rates of P (0, 2.2, 4.4, 8.8, and 17.6 kg P ha−1). A significant response to P was obtained at rates up to 17.6kg P ha−1. There was no significant difference due to source of P in terms of sorghum grain yield or total P uptake. Both Olsen and Bray 1 soil tests underestimated P availability from PAPR with respect to that from SSP. A rapid rate of P uptake was observed during grain filling to maturity (81–102 days), when 40% of the total P was taken by the plant. The internal efficiency of both P sources was the same.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749945
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  • 4
    Electronic Resource
    Electronic Resource
    Alleviating soil fertility constraints to food production in West Africa: Efficiency of nitrogen fertilizers applied to food crops (1991)
    Springer
    Nutrient cycling in agroecosystems 29 (1991), S. 21-33 
    Details
    ISSN: 1573-0867
    Keywords: Nitrogen ; urea ; calcium ammonium nitrate ; cropping density ; N use efficiency ; slow release ; urease inhibitors ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An overview is provided of the N efficiency research conducted within the West African Fertilizer Management and Evaluation Network (WAFMEN). Factors such as N rate, mode of N fertilizer application and choice of N sources for different agroecological zones of West Africa are discussed in relation to crop yield response. The interactive effects of cropping density and rainfall on N efficiency and yield are examined with particular emphasis on production of millet in Niger. The potential role of new, slow-release fertilizers as well as urea amended with urease inhibitors is mentioned in relation to present and future fertilizer N requirements in West Africa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048986
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  • 5
    Electronic Resource
    Electronic Resource
    Impact on ammonia volatilization losses of mixing KCl of high pH with urea (1994)
    Springer
    Nutrient cycling in agroecosystems 40 (1994), S. 89-92 
    Details
    ISSN: 1573-0867
    Keywords: KCl ; ammonia volatilization ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonia volatilization associated with urea hydrolysis has been shown to be primarily associated with the pH of the soil solution and its buffering ability in the immediate zone of the fertilizer granule. Numerous studies have also shown that these losses can be reduced significantly by the addition of large amounts of KCl with the urea. Because the pH of commercial sources of potash ranges from 6.5 to 9.5, investigations were conducted to determine if the high pH of these K sources had an effect on the ammonia lost from three contrasting soils. Despite large ammonia losses (approximately 50% of N applied) and a significant reduction in loss due to the use of KCl (30%-50% reduction), the experiments showed no effect of potash pH on ammonia loss. It may be concluded that no risk of enhanced ammonia loss can be associated with the use of high-pH potash sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750092
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of five soil testing methods to establish phosphorus sufficiency levels in soil fertilized with water-soluble and sparingly soluble-P sources (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 271-279 
    Details
    ISSN: 1573-0867
    Keywords: Bray P1 ; Bray P2 ; Mehlich 1 ; Olsen ; water-extractable P ; phosphate rock ; partially acidulated phosphate rock ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field experiments were conducted in Niger with pearl millet (Pennisetum glaucum [L] R. Br.) in which the crop was fertilized with phosphate rock (PR) from two deposits from Niger (Tahoua and Parc W). The PR was applied either as ground rock or as partially acidulated phosphate rock (PAPR) and was compared to water soluble sources (TSP and SSP) in terms of millet yield response. The ability of five soil testing procedures (Bray P1, Bray P2, Mehlich 1, Olsen, and water extraction) to establish P sufficiency levels for millet was tested. The results of all soil testing methods were highly correlated amongst each other for the treatments receiving water-soluble fertilizers or PAPRs. None of the soil testing procedures which were evaluated was able to accurately measure available P when PRs were applied. Sufficiency levels were calculated for the PAPR and water-soluble fertilizers using nonlinear regression analysis and a graphic procedure for each of the P soil testing methods. The Bray P1 method appeared to be the most reliable procedure and was used to study the effect of accumulated total or total water + citrate-soluble P rates on final P availability. A single quadratic function was able to describe this effect when the P rates were expressed as water + citrate-soluble P for both PAPRs and water-soluble fertilizers independently of the P fertilizer source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054328
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of crop residue and fertilizer use on pearl millet yields in Niger (1993)
    Springer
    Nutrient cycling in agroecosystems 34 (1993), S. 251-258 
    Details
    ISSN: 1573-0867
    Keywords: nutrient recycling ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was conducted over a 4-year period in Niger, West Africa, to determine the effects of crop residue (CR), fertilizer, or a combination of crop residue and fertilizer (CRF) on yields of pearl millet (Pennisetum glaucum [L.] R. Br.). Despite a decline in yields of control plots (initial yields were 280 kg grain ha−1 declining to 75 kg grain ha−1 over 4 years), yields of fertilizer plots were maintained at 800–1,000 kg grain ha−1. Continued application of CR slowly augmented yields to levels similar to those of the fertilized plots. The effects of CR and fertilizer were approximately additive in the CRF plots. Addition of CR and fertilizer increased soil water use over the control by 57 mm to 268 mm in an average season and helped trap wind-blown soil. These plots tended to exhibit slightly higher soil pH and lower Al saturation than did the fertilized treatments. Return of CR to the soil resulted in significantly reduced export of most plant nutrients, especially Ca, Mg, and K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750571
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  • 8
    Electronic Resource
    Electronic Resource
    Agronomic assessment and 15N recovery of urea amended with the urease inhibitor nBTPT (N-(n-butyl) thiophosphoric triamide) for temperate grassland (1994)
    Springer
    Plant and soil 161 (1994), S. 167-177 
    Details
    ISSN: 1573-5036
    Keywords: ammonia volatilization ; N-(n-butyl) thiophosphoric triamide ; 15N recovery ; temperate grassland ; urea ; urease inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three field experiments were undertaken concurrently at one site to evaluate a range of surface-applied nBTPT-amended urea products (0.01, 0.05, 0.1, 0.25 and 0.5% nBTPT w/w) on NH3 volatilization, grass yield and 15N recovery in the plant-soil system. Each experiment was repeated on five separate occasions over the 1992 growing season to cover a range of weather conditions. Total NH3 loss from unamended-urea ranged from 5.5% in early May to 20.8% in June. The inhibitor was highly effective in reducing ammonia volatilization and delaying the time at which maximum rate of NH3 loss occurred. Over all time periods the % inhibition was 50.4, 82.8, 89.0, 96.5 and 97.0% at the 0.01, 0.05, 0.1, 0.25 and 0.5% nBTPT levels respectively. There was no significant difference in the overall % inhibition in ammonia loss at different times suggesting that the effectiveness of the inhibitor was not dependent on climatic conditions. Over all times incorporation of nBTPT at the 0.05% level increased dry-matter yield by 9% compared to urea alone and increased the shoot recovery of N from 66.7% to 80.9%. Nitrogen saved from volatilization was taken up by the plant, however, the subsequent translation into dry-matter yield appeared to be adversely affected at the high inhibitor rates. There was no significant effect of inhibitor on 15N recovery in soil at any depth down to 15 cms. nBTPT significantly increased (p 〈 0.001) the % N derived from fertilizer (% N dff) in the shoot compared to unamended-urea and increased (p 〈 0.01) the shoot recovery of 15N from 32% up to 39%. Total 15N recovery in the soil-plant system was increased by up to 17% by amending urea with nBTPT. This urease inhibitor has been shown to improve the efficiency of urea however, its potential for the European market will be dependent on economic factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046388
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of soil tillage and fertilizer use on pearl millet yields in Niger (1990)
    Springer
    Plant and soil 123 (1990), S. 51-58 
    Details
    ISSN: 1573-5036
    Keywords: millet ; Niger ; partially acidulated phosphate rock ; phosphorus placement ; phosphate rock ; tillage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Farmers in Niger generally do not plow their fields and are therefore unable to incorporate phosphate. Experiments were conducted in Niger to assess the effect of soil tillage, P source, and fertilizer placement on yields of pearl millet (Pennisetum glaucum [L.] R. Br.). Treatments included single superphosphate (SSP) or ground Tahoua phosphate rock (PRT) incorporated into the soil during tillage or SSP surface applied after tillage. In plots which were not tilled, P sources (SSP, PRT, and PAPR-partially acidulated rock) were broadcast on the soil surface with no incorporation. In order to improve P efficiency under zero tillage, P was point placed in the soil near the plant with either broadcast or point-placed urea. Treatments in which tillage was used showed a slight though nonsignificant yield increase over untilled plots. The yield increase did not appear to be due to phosphate incorporation but rather to direct tillage effects on early plant growth. In a comparison of SSP with PRT or PAPR broadcast on soils not receiving tillage, PRT performed poorly relative to the other P sources. SSP outyielded PAPR and PRT in 1986, but in subsequent years, no significant difference was found between PAPR and SSP. Point placement of P or N near the plant did not significantly increase yields over broadcast treatments even though the millet was planted with wide 1×1 m spacing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009925
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  • 10
    Electronic Resource
    Electronic Resource
    Fate and efficiency of N fertilizers applied to pearl millet in Niger (1990)
    Springer
    Plant and soil 125 (1990), S. 221-231 
    Details
    ISSN: 1573-5036
    Keywords: calcium ammonium nitrate (CAN) ; 15N ; urea ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field studies were conducted in Niger using 15N-labeled fertilizers to assess the fate and efficiency of fertilizer N in pearl millet (Pennisetum glaucum [L.] R.Br.) production. Total plant uptake of fertilizer N was low in all cases (20%–37%), and losses were severe (25%–53%). The majority of N remaining in the soil was found in the 0- to 15-cm layer though some enrichment at lower depths was found when the N fertilizer was calcium ammonium nitrate (CAN). In a comparison of urea placement methods (band, broadcast, or point placement), no significant differences in 15N uptake or yield were noted though point placement did exacerbate 15N loss. The mechanism of N loss is believed to have been ammonia volatilization. Yields were similar whether urea or CAN was used, but 15N uptake from CAN was higher. A statistical model was developed relating millet yield and N response to midseason rainfall. In drought years, no N response was found, whereas in years of good rainfall a response was found of 15 kg grain for each kilogram of N applied (at 30 kg N ha-1 rate).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010660
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