Quantity-intensity characteristics of Potassium (K) in relation to potassium availability under different cropping system in alluvial soils

Potassium availability to the plant is influenced by internal soil properties and other external properties. Quantity intensity characteristics are one of the satisfactory measures of potassium dynamics and its availability. So quantity intensity characteristics of potassium were studied to quantify the potassium availability in three different cropping systems viz., paddy-paddy, banana and paddy-pulse based. Three soil profiles were studied in each cropping system and soil samples were collected horizon wise for laboratory analysis. Q/I parameters were estimated by the method adopted by Beckett (1964a). Analysis of variance was performed to compare the impact of cropping system and pedons on different chemical and nutrient properties of soils. Significantly high organic carbon (0.47%), and available nitrogen (271.10 kg/ha), medium available phosphorus (17.00 kg/ha) and available potassium (230.50 kg/ha) recorded in paddy-pulse cropping system compared with other cropping system. Banana based cropping system recorded significantly higher clay (41.2%), soil reaction (8.24) and potassium fixing capacity (84.32%). The results of Quantity-Intensity (Q/I) dynamics studies shows that paddy-pulse based cropping system recorded high labile K KL (0.49 c mol (p+)/kg) and Potential buffering capacity PBCK (45.67 c mol (p+)/kg) whereas paddy-paddy cropping system recorded PBCK of 16.81 c mol (p+)/kg which needs frequent potassium fertilization. The results showed that most of the soil properties including K dynamics were greater extent influenced by changes in cropping systems which consecutively affects the potassium availability.   Key words: Quantity intensity (Q/I) characteristics, cropping systems, soil properties, K dynamics.