Effects of different Mg fertilizer sources on the magnesium availability in soils
- 418 Downloads
Pot experiments with different soils were conducted to determine the effect of different Mg fertilizer sources on magnesium availability. The sources studied included Kieserite (MgSO4 H2O), a synthetic magnesium sulphate (SMS) with variable content of crystal water and a calcined magnesite (Mg-oxide). The three magnesium fertilizers vary greatly in their solubility in water, affecting the availability to plants once applied to the soil. Whereas Kieserite dissolved gradually and SMS immediately, Mg-oxide released only insignificant amounts of Mg in cool water (20 °C) after intensive stirring. Due to the fact that these dissolution properties may distinctly affect Mg availability in soils, Kieserite as a standard magnesium source was tested against a slow release Mg-oxide in the fine and the coarse form. Soil extraction of samples taken from 0–10 and 10–20 cm depths at 4, 8 and 12 weeks after applying the fertilizers to the soil surface revealed that the rate at which Mg appeared in the available pool (CaCl2 extracts) varied significantly between Mg sources. Mg availability from Kieserite was much greater than from Mg-oxide. Nutrient availability from Mg-oxide depended on the fineness of the material, i.e. the coarser the less available. Maize grown as test plant in the pots revealed a 10.6% larger yield and 19.6% larger Mg uptake in Kieserite than in Mg-oxide treated pots. High solubility of a fertilizer under high rainfall conditions, however, may also affect the Mg availability through large losses occurring by Mg leaching. Therefore, in a second experiment, the behaviour of surface applied magnesium fertilizers, Kieserite versus a quickly dissolving synthetic magnesium sulphate (SMS) was studied, using an Ultisol (Serdang Series soil from Malaysia). A simulation of high rainfall by excessive irrigation of 20 mm per day over a period of 16 days to a water saturated soil revealed that the amount of Mg lost by leaching differed between the two Mg sources tested. The lowest amount with 8.7% of the applied Mg was lost in the Kieserite treatment at the low application rate and the highest with 22.3% in the SMS treatment at the high application rate. It is concluded that a gradual but strong release to match plants requirements is the most desired characteristic to maximize crop uptake and minimize losses.
Unable to display preview. Download preview PDF.
- Durrant M.J. and Draycott A.P. 1976. Improvements in calcined magnesite as a magnesium fertilizer. J. Agric. Sci., Camb., 86: 543–552.Google Scholar
- Härdter R. 1992. Magnesium-The forgotten macronutrient. IFA-FADINAP Regional Fertilizer Conference for Asia and the Pacific.Google Scholar
- Bali, Indonesia, Nov. 29-Dec. 2, 1992, International Fertilizer Association, Paris, France, 16 pp.Google Scholar
- Heming S.D. and Hollis J.F. 1995. Magnesium availability from Kieserite and calcined magnesite on five soils of different pH. Soil Use Manage. 11: 105–109.Google Scholar
- Lau C.H., Mahmud A.W. and Zainab Hamzah 1994. Chinese magnesium sulphate as magnesium fertiliser for Hevea. Planters' Bulletin, No. 220–221, Rubber Research Institute of Malaysia, pp. 40–43.Google Scholar
- Sher D. 2002. Understanding magnesium fertilisers for better results. The Orchardist, New Zealand, Febr. 2002, pp. 18–19.Google Scholar
- Tang M.K., Mohd Nazeeb and Loong S.G. 2001. Oil palm responses to different sources of magnesium on an inland reworked soil in Peninsular Malaysia. Proc. 2001 PIPOC International Palm Oil Congress (Agriculture), pp. 261–271.Google Scholar