The great earthquake of 2011 triggered a tsunami that damaged large areas of paddy fields in northeastern Japan. In an effort to address the salt damage, supplementation of Ca-containing materials to exchange Na adsorbed on soil surface has been recommended. In addition, Si has also been shown to enhance paddy growth. Steelmaking slag, which contains a water-soluble solid solution phase of 2CaO·SiO 2 , can supply Ca and Si for soil remediation. In this study, the dissolution behaviors of nutrient elements from fertilizer made of steelmaking slag were investigated using the column test. In addition, crop cultivation experiments were also conducted using tsunami-damaged paddy fields. In column test, Ca content in soil solution increased by the application of fertilizer made of slag, but the Na content did not change significantly. These trends were also observed in the pore water of the actual paddy in crop cultivation experiments. In addition, the incremental trend of silicate content in the pore water by the application of fertilizer made of slag was more apparent than that in the column test. Paddy growth was enhanced and the yield of brown rice was increased by the application of fertilizer made of slag. In conclusion, the fertilizer made of steelmaking slag has the following three effects: (1) mitigating the damage caused by the Na ion through the supplementation of Ca, (2) enhancing the mineralization of soil N by increasing the pH, and (3) accelerating photosynthesis by the supplementation of silicate.
The available phosphorus (P) in soil is a major limiting factor for maize productivity in the Nacala corridor, Mozambique. In this study, soils were collected from three representative sites, Ribaue, Nampula, and Nacala, in the area, and each was used for maize pot experiment with five P fertilizer levels. The soil-available P content was determined by the Mehlich-3 method at 30 days after P fertilization. The shoot biomass and P concentration at the tasseling stage increased as the P fertilizer level increased and were significantly expressed as a function of soil-available P. Based on the function, the available P that attains 90% of the maximum shoot biomass was estimated as 79 mg P 2 O 5 kg −1. Consequently, the results in this study suggest a recommendation of 32-74 kg P 2 O 5 ha −1 fertilizer for maize production in the Nacala corridor although a field evaluation and economical evaluation are necessary.
Mehlich 3 (M-3) is a multi-nutrient extractant which provides a rapid and cost-effective soil test for various soils. This study investigated the applicability of M-3 for cation and micronutrient determination under the specific soil fertilization and crop rotation given in northern Mozambique. Cations and micronutrients extracted with M-3 were compared with the classical methods; neutral ammonium acetate (NH 4 OAc) for calcium (Ca), potassium (K), magnesium (Mg), and sodium (Na); diethylene triamine penta-acetic acid (DTPA) for copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn); and Bray I for phosphorus (P). Results indicated that M-3 was useful for Ca, K, Mg, P and Zn determination. Various types of soil fertilization or crop rotations did not alter the accuracy and precision of cation determination using M-3 and NH 4 OAc. Addition of organic and chemical fertilizers was thought to adversely affect the quantity of M-3 and DTPA extractable micronutrients and their correlations. However, levels of M-3 micronutrients in soils were well above those considered to be critical levels as same as that of DTPA. This suggested that M-3 was an acceptable procedure for determining cations and micronutrients in the routine analysis and could be advantageous for soil nutrient management in the specific conditions given.
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