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Ammonium Sulphate

Oct 09

Include Ammonium Sulphate in your fertilizer program

By FERTILIZER PRODUCTS, Nitrogen, Nitrogen Products, PLANT & SOIL NUTRITION No Comments

AFRIKAANS: Maak Ammoniumsulfaat deel van jou bemestingsprogram Specific applications of Ammonium Sulphate may serve as an important source of Nitrogen (21% N) and Sulphur (24%S), for crop production. Ammonium Sulphate can generally be regarded as a suitable supplemental source of nitrogen (N), which can address all Sulphur(S) requirements. Under specific conditions the use of Ammonium Sulphate can result in higher grain yields compared to other N-sources when used as the primary N-source. Before planting Large quantities of Ammonium Sulphate can be broadcast before planting under Centre Pivot Irrigation, especially when soil pH is high and where considerable quantities of plant residues are incorporated in the soil. The volatilization of Ammonium Sulphate is relatively low compared to other N sources, however volatilization can be significant under alkaline conditions and therefore Ammonium Sulphate should rather be incorporated. The application of Ammonium Sulphate as the main source of N before planting could result in higher grain yields compared to other N-sources under specific conditions (Figure 1). Possible reasons for higher yields obtained with Ammonium Sulphate compared to other N-Sources as in Figure 1: Wheat response to S due to S-deficiency in the soil. Less leaching compared to other N-Sources. Under strong alkaline conditions the greater acidifying effect of Ammonium Sulphate can enhance the uptake of other plant nutrients. In Plant Mixtures All N in Ammonium Sulphate is in the ammonium (NH4+) form while most crops prefer a combination of both nitrate (NO3–) and ammonium. Furthermore the conversion of ammonium-N to nitrate-N is usually very slow when band placed. Relatively small amounts of Ammonium Sulphate are incorporated in some granular and liquid plant mixtures to increase the sulphur and ammonium content. Extra ammonium in the plant mixture will accordingly reduce leaching of N in the plant mixture. The application of Ammonium Sulphate as the only source of N in plant mixtures is not recommended. After planting Large quantities of Ammonium Sulphate can be broadcast after planting as the main N-source, either through spreading or Centre Pivot applications. As previously indicated soil incorporation is preferred. The practice of applying up to 100kg Ammonium Sulphate/ha over maize plant rows directly after planting serves as an insurance against possible leaching losses of N in plant mixtures and an effective way of meeting all crop S requirements. The band placement of large quantities of Ammonium Sulphate as the main source of N after planting is not recommended. Mixtures of LAN and Ammonium Sulphate in a ratio of 75% LAN : 25% Ammonium Sulphate (marketed as KANAS by some local fertilizer suppliers)  combines the optimal benefits of both products and contains 26.25% N and 6% S. This ratio of N : S closely resembles the requirement of many crops, with the added benefit that the N is applied in both the ammonium and nitrate forms. Similarly AS is mixed with Ammonium Nitrate Solution to provide a liquid product called Ammonium Sulphate Nitrate (ASN) containing 18% N and 2.4% S. Relatively large quantities of either KANAS or ASN may be…

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Sep 21

Leaching of different N Sources

By Nitrogen, Nitrogen Products, PLANT & SOIL NUTRITION No Comments

AFRIKAANS: Verskille in loging tussen Stikstofbronne Inorganic nitrogen (N) dissolved in groundwater could be lost for crop production through downward and sideway movements of groundwater, resulting in lower yields and profit margins above costs. Differences in leaching between N sources can effectively be utilized to reduce the risk of N leaching. N management practices such as application methods and timing could also contribute significantly to reductions in leaching losses. Basic scientific principles and case studies associated with severe losses in revenue were used to develop guidelines for combatting N leaching losses. The application of different N-sources results in one or a combination of nitrate-N, ammonium-N and urea-N dissolved in groundwater. The vertical movement of these forms of inorganic N in groundwater are displayed for a Sandy Loam soil in Figures 1 and for a Clay Soil in Figure 2. Ammonium-N resulted in very little leaching but large portions of the applied Nitrate-N en Urea-N moved with the groundwater to the level of water penetration. A little bit more Ammonium-N moved into the Sandy Loam soil compared to the Clay Soil but these amounts were insignificant for both soils. Larger portions of the applied Urea-N and Nitrate-N moved with the groundwater to the level of water penetration in the Sandy Loam soil compared to the Clay soil. Half of the LAN will show a similar response to Ammonium Sulphate and the other half similar to Calcium Nitrate since LAN consists of 50% Ammonium-N and 50% Nitrate-N. According to Figures 1 and 2 the immediate leaching potential of LAN is about 50% less than that of Urea. Ammonium-N could however over time be converted to leachable nitrate-N through the process of nitrification. The effect of LAN which was applied shortly before planting and at planting, followed by heavy downpours, resulting in severe leaching are presented in Figure 3. Severe N deficiencies in leaves and in the soil up to a depth of 60 cm have been confirmed with this case study. Yield loss as a result of N leaching was estimated between 7 and 8 ton/ha. Although risks of N-leaching are much less with LAN compared to Urea it is recommended that neither LAN nor urea be applied before planting on well drained soils. The effect of vertical as well as lateral movement of applied N due to excess rain is visible in Figure 4. N analysis in a strip over the rows to a depth of 750 mm was 39 kg/ha for A where the maize was yellow and stunted but 179 kg/ha where the maize was much more prolific and also greener. N analysis between the rows where N was not applied was 32 kg N/ha in the top 60 cm soil for both A and B. Variation in crop growth was therefore directly related to variation in soil N analysis over rows. This effect is often observed under high rainfall conditions on sandy soils, irrespective of time of N application. These symptoms are often incorrectly ascribed to poor fertilizer quality…

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Sep 14

Volatilization differences between N sources

By FERTILIZER PRODUCTS, Nitrogen, Nitrogen Products, PLANT & SOIL NUTRITION No Comments

Afrikaans Version: Verskille in vervlugtiging tussen Stikstofbronne Volatilization of applied nitrogen (N) is primarily in the form of ammonia (NH3), although losses in the form of atmospheric N (N2 and N2O) may also occur when soils are waterlogged. Ammonia is released from ammonium (NH4+) containing and forming fertilisers when there is insufficient soil water present in which the ammonia can dissolve. This will also occur when fertilisers are applied and left remaining on or close to the soil surface. Atmospheric nitrogen is formed from nitrate nitrogen (NO3–) when the topsoil is waterlogged and deprived of oxygen for long periods. Water scarcity rather than long periods of water logging are far more common in South Africa. This article therefore focusses on ammonia losses from applied fertilisers combined with factors affecting this process such as soil pH and temperature. The efficacies of urease inhibitors which delay the conversion of urea to ammonia together with other possible solutions for the problem of ammonia volatilization are also discussed. Soil pH significantly affects Ammonia volatilization losses. Ammonia losses from urea were increased by 18% over five soils when the pH was increased from 6.5 to 9.1 (Figure 1). Most losses occurred from urea, followed by DAP, Ammonium sulphate, MAP and LAN (Figure 1). The difference in ammonia volatilization between urea and LAN was 15% at a pH of 9.1 (Figure 1). The conversion of urea to ammonium and also DAP to ammonium are alkaline reactions. This explains why these products will lose more N in the form of ammonia than other products, forming or releasing similar quantities of ammonium with no increase in pH. High application rates of urea or DAP which would result in high concentrations on the soil surface will increase soil pH more and consequently more ammonia will be formed and lost. Nitrogen loss in the form of ammonia could be much higher than indicated in Figure 1. Du Preez & Burger (1986) showed ammonia losses of 55% which resulted from urea applications at a rate of 240 kg N/ha, on a soil containing 50% clay and which had an original pH (H2O) of 7.5. Botha & Pretorius (1988) showed ammonia losses of as much as 61% following urea applications at a rate of 83 kg N/ha on a soil with a clay content of 9.5% and a pH (H2O) of 7.9 after urea applications. Fenn & Miyamoto (1981) showed ammonia losses of 66% following urea surface applications on a soil with a pH (H2O) of 7.8. Ammonia losses are significantly affected by temperature. As temperatures increased from spring to mid-summer ammonia losses increased tremendously when using urea but also significantly with UAN (Figure 2). Ammonia losses from LAN however remained very low with increasing temperatures (Figure 2). Hoeft, et.al. (2000) stated that the potential for urease inhibitors to be effective would be best above 10° C. Urease inhibitors such as Agrotain, SKW Piesteritz and Hanfeng Evergreen delay the conversion of urea to ammonia and therefore also the release of ammonia. The…

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