Fractions, uptake and fixation capacity of phosphorus and potassium in three contrasting soil orders

Journal of Soil Science and Plant Nutrition, 2014, 14 (3), 640-656 RESEARCH ARTICLE Fractions, uptake and fixation capacity of phosphorus and potassium in three contrasting soil orders D. Chatterjee1,2, *, S.C. Datta1 and K.M. Manjaiah1 Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi- 110 012, India. 2ICAR Research Complex for NEH Region, Nagaland Centre, Jharnapani, Medziphema, Nagaland- 797 106, India. *Corresponding author: 1 Abstract A controlled greenhouse experiment was conducted to study the fraction, uptake and fixation of phosphorus (P) and potassium (K) in three soils with contrasting characteristics. The experiment was carried out in two phases, viz., sorghum-Sudangrass depletion and test crop experiment with maize with three levels of fertility status (depleted, original and fertilized with 40 mg kg-1 P and K) and two levels of rhizospheric status (rhizosphere and non rhizosphere). Clay was separated by ultrasonic vibration followed by fractionation into colloidal and non colloidal clay and short-range order (SRO) minerals, P and K fixation were measured in these clays. Phosphorus and potassium fractions and uptake were measured in soil samples. The results showed that, available and non-exchangeable potassium was highest in Vertisol and Inceptisol, respectively. Calcium-P was the dominant fraction in soil and highest in Inceptisol. Maximum K-fixation capacity for both the clay fractions was found in Vertisol (32.57% for colloidal clay and 37.94% for non colloidal clay), depleted soils (30.58% for colloidal clay and 31.04% for non colloidal clay) and rhizosphere (28.34% for colloidal clay and 29.59% for non colloidal clay). Phosphorus fixation was highest in Alfisol (58.72% for colloidal clay and 67.26% for non colloidal clay), depleted fertility status (53.41% for colloidal clay 55.45% for non colloidal clay) and non-rhizosphere (52.53% for colloidal clay and 54.26% for non colloidal clay) for both the clays. Phosphorus fixation was positively correlated with different pools of iron and aluminum compounds whereas, potassium fixation showed positive significant correlation with amorphous ferri-alumino silicate content. Keywords: Clay, fixation, phosphorus, potassium, Alfisol, Vertisol, Inceptisol, maize, short-range order mineral Abbreviations: LMOWAs low-molecular weight organic acids, P phosphorus, K potassium, AFAS amorphous ferri-alumino silicate, SRO short-range order, NEK non-exchangeable potassium, Ca-P- calcium P fraction 640 641 Chatterjee et al. 1. Introduction Fixation of plant nutrients is the major concern for economical use of fertilizer. Huge amount of applied phosphorus (P) and potassium (K) are fixed into the soil in such a form, which is not readily available to the plants. This is a soil problem and to meet the plants’ need, a higher dose of nutrient is required. Phosphorus fixation in soils depends upon many factors, viz., the pH of the soil, organic matter content, type of clay and sesquioxides etc. Potassium is second only to nitrogen (N) in the quantities required by plants; hence its fixation is also a matter of apprehension. Potassium fixation capacity of the chemically synthesized amorphous minerals was reported in the range of 2-6 meq 100 g-1 (Van Reeuwijk and De Villiers, 1968). The effect of low-molecular weight organic acids (LMWOAs) on the sorption and desorption of phosphorus by clay minerals was established since fifties. Hydrous oxides of aluminum and iron were mostly responsible for the fixation of phosphate in soils. Research work revealed that tri and di-carboxylic acids were effective in reducing phosphate sorption, whereas monocarboxylic acids had little effect on phosphate fixation (Violante et al., 1996). The clay size inorganic colloidal fraction of soils contains appreciable quantities of 'free' and ‘combined' oxides of Si, Al and Fe, known as short-range order (SRO) minerals. For example, allophane, protoimogolite allophane, imogolite, allophane like constituents, imogolite like constituents, ferrihydrite, etc. Since the size of these minerals fall under 1-100 nm range, these can be considered as soil inherited nano-minerals. Volcanic ash soils, by virtue of the shortrange order variable charged nano-materials (allophane, imogolite, aluminum (Al) and iron (Fe) oxides) and organo-mineral complexes, may adsorb high amounts of phosphate characterized by high surface area and reactivity (Vacca et al., 2003). The chelation of P-fixing elements by LMWOAs could be another mechanism governing the role of plant materials in P solubilization in the rhizosphere or decomposition system. Under K-stress environment, K from nonexchangeable pool replenishes the available pool which contributes in plant K uptake (Srinivasarao et al., 2007). Studies have shown that a significant portion of K (70–90%) required by plants comes from the nonexchangeable pool in the absence of easily supplied K, thus indicating the beneficial role of the fixed K. The quantity of interlayer K in vermiculite and illite containing soils high compared with the amount of K taken by crops. This interlayer K is also the major source controlling the long-term K supplying potential of soils. Soils derived from volcanic materials have a strong K+ or NH4+ retention (Escudey et al., 1997). But, no common mechanism has been identifiedaccount for this high K selectivity. Niebes et al. (1993) reported that the contribution of non-exchangeable K to K uptake ranged from 50% in the fine clay to 80-100% in the coarser fractions and due to high supplying power and their relative abundance, the silt fractions provided a major part of the supply of K. Potassium fixation capacities of some Inceptisols of India were decreased with increasing size of the clay-humus complex (Kumar et al., 2004) and the removal of allophane, peroxidation and CBD treatment resulted in an increase in K-fixation capacity. There is a very scanty of work on the role of the shortrange order minerals in P and K fixation capacity. Moreover, most of the studies are made under artificial environment with synthetic materials. So far, under the complexity of natural soil environment a few attempts might be made. Keeping all the above facts under consideration, a study was conducted on phosphorus and potassium fractions, uptake and fixation capacity in relation to plant roots mediated changes of SRO minerals. 2. Materials and Methods 2.1. Collection and properties of initial soil samples Three soils representing soil orders viz. Alfisol (Typic Haplustalfs), Inceptisol (Typic Haplustept) P & K fraction, uptake, fixation and Vertisol (Typic Haplustert) from Parvathipuram (Andhra Pradesh), IARI research farm (New Delhi) and Rajahmundry (Andhra Pradesh), respectively was used for the present study. The surface (0-15 cm) soil samples were collected, ground and passed through 2-mm sieve and characterized for physico-chemical properties and mineral (...truncated)