international fertilizer correspondent No 5

LATEST RESEARCH FINDINGS - a selection of research papers from the semi arid/arid region

Tariq Siddique, M. Ilyas and Aslam John: Evaluation of chemical extractants for K release and their correlation with K uptake by wheat in different soil series of Punjab. Pak. J. Soil Sci. 15: 16-20, 1998.

A pot experiment was conducted to test five extractants for K extraction from six soil series in Punjab, Pakistan for their correlation with K uptake by wheat. The efficiency of the extractants was in the order of H₂O < CaCl₂ < MgOAc < NH₄OAc < HNO₃. Significant correlation was found between extracted soil K and K in grains and straw. It is suggested that 1 N NH₄OAc, 0.5 N MgOAc or 0.025 N CaCl₂ can be used for K indexing.

Muhammad Idris and Muhammad Shafiq: Response of cumin (Cuminum cuminum) to various fertilizer levels. Pak. J. Soil Sci. 15: 44-46, 1998.

Cumin holds an important economic position in the agriculture of Baluchistan, Pakistan, but farmers in this area are not aware of the importance of fertilizers. The study was conducted to find out the most suitable combination of NPK. The highest seed yield (1180 kg/ha) was recorded with 120-60-30 kg/ha N-P₂O₅-K₂O.

Awan, Z.I., M. Arshad, and M.S. Akthar: Potassium release characteristics of sand and silt in relation to soil parent material and weathering stage. Pak. J. Soil Sci. 15: 94-105, 1998.

The study was conducted to determine the non-exch. K pool of the sand and silt fraction in soils in relation to their mineralogical composition. In less weathered alluvial soils the sand fraction released higher K quantities in boiling HNO₃ acid. In moderately weathered soils the silt fraction became the major source of K released in boiling HNO₃. Highly weathered soils released lower HNO₃ extractable K from the sand and the silt fraction than other alluvial soils, which suggested that HNO₃ extracted K follows the degree of profile development.

Awan, Z.I., M. Arshad, and M.S. Akthar: Potassium fixation in relation to soil parent material and weathering stage in Pakistan. Pak. J. Soil Sci. 15: 106-115, 1998.

Potassium fixation in alluvial soils is influenced by the weathering stage. Moderately weathered soils were found to have the highest fixation capacity compared to highly weathered or less weathered soils. In contrast to other findings, K fixation did not relate to the clay content.

Mirza B. Baig, M. Sharif Zia, M.T. Rashid, M. Aslam, M. Salim and M.B. Tahir: Sorghum growth and chemical composition as influenced by potassium fertilization and moisture regimes. Pak. J. Soil Sci. 15: 84-88, 1998.

In a greenhouse study the effect of K sources, the rate of application and moisture regimes was investigated on sorghum yield and K and S uptake. Use of potassium sulphate gave higher dry matter yield and led to higher K and S uptake than potassium chloride. Soil water depletion reduces dry matter yield of sorghum and affected K and S uptake.

Murugappan, V., P. Santhy, D. Selvi, P. Muthuvel and M. Dhakshinamoorthy: Land degradation due to potassium mining under high intensive cropping in semi arid tropics. Fertiliser News, 44 (5), pp. 75-77, 1999.

The effect of potash use on the soil K status was investigated in South India in a long-term experiment with a finger millet-maize-cowpea rotation. The results indicate that none of the crops responded to potash use because of the high level of initial soil K. However, over the years, total K and exchangeable K levels in soils were found to decline, irrespective of the nutrient input, i.e. whether K was added or not. The strongest soil K depletion occurred under the N and NP treatment. The observed K depletion in cases where K fertilizers were added suggests higher K uptake due to luxury consumption. The observed soil K mining would in the long run limit crop yields and render the land chemically degraded.