1. Ahmad M, Amin R (1986) Distribution of higher categories of soil taxonomy in Pakistan. In: Proc XII int forum on soil taxonomy and agrotechnology transfer. Soil Surv Pak, Islamabad, pp 31?44
2. Ahmad I, Rahman S (1984) Yield, protein and amino acid composition of wheat grain (Triticum aestivum) as influenced by potash fertilizer. Pak J Agric Res 5:96?101
3. Bajwa MI (1989) Potassium mineralogy of Pakistani soils and its effect on potassium response. In: Tahis Saleem M (ed) Potassium and fertilizer use efficiency. National Fertilizer Development Centre of Pakistan, Islambad, pp 203?216
4. Bergmann W (1988) Ernährungsstörungen bei Kulturpflanzen, Entstehung, visuelle und analytische Diagnose. Gustav Fischer Verlag, Jena
5. Bernas B (1968) A new method for decomposition and comprehensive analysis for silicates by atomic spectrophotometry. Anal Chem 40:1682?1687