Effect of potassium on soil conservation and productivity of maize / cowpea based crop rotations in the north - west Indian Himalayas.

Abstract

Plots under conservation tillage may require higher amount of potassium (K) application for augmenting productivity due to its stratification in upper soil layers , thereby reducing K supplying capacity in a medium or long- term period. To test this hypothesis , a field experiment was performed in 2002- 2003 and 2006- 2007 to study the effect of K and several crop rotations on yield, water productivity , carbon sequestration, grain quality, soil K status and economic benefits derived in maize ( Zea Mays L) cow pea ( vigna snensis L) based cropping system under minimum tillage ( MT) . All crops recorded higher grain yield with a higher dose of K( 120 kg K2O ha -1) than recommended K( 40 kg K2 ha-1) . The five years average yield data showed higher K application ( 120 kg K2O ha-1) produced 16.4% (P<0.05) more maize equivalent yield. Cowpea based rotation yielded 14.2% ( P,0.05) higher production tha maize based rotation. The maximum enhancement was found in cowpea - mustard rotation. Relationship between yield and sustainable indices revealed that only agronomic efficiency of fertilizer input was significantly correlated with yiled. Similarly, higher doses of K application not only increased the water use efficiency (WUE) of all crops , but also reduced runoff and soil loss by 16.5% and 15.8% under maize and 23.3% and 19.7% under cowpea cover, respectively. This study also revealed that on an average 16.5% of left over carbon input contributed to soil organic carbon (SOC) . Here, cowpea based rotation with the higher K application increased carbon sequestration in soil. Potassium fertilization also significantly improved nutritional value of harvested grain by increasing the protein content for maize by ( 9.5%0 )and cowpea by ( 10.6%). The oil content in mustard increased by 5.0% and 6.0% after maize and cowpea, respectively. Net return also increased with the application f the higher K than recommended K and the rend was similar to yield. Hence, the present study demonstrated the potential yield and profit gains along with resource conservation in the Indian Himalayas due to annual additions of higher amount of K than the recommended dose. The impact of high K application was maximum in the cowpea - mustard rotation.