Potassium and crop rotation impact on productivity and resource conservation in maize and cowpea based cropping systems

Conservation tillage requires higher amount of potassium application for augmenting crop productivity due to its stratitification (reduction in K supplying capacity in medium and long-term duration) in upper soil layer. To address this issue, a field experiment was carried out for five years (2002–03 to 2006–07) at Central Soil and Water Conservation Research and Training Institute, Research Farm, Selakui, Dehradun, Uttarakhand on a land with a gentle slope (2%) to study the effects of higher K application on grain yield, soil K status, carbon sequestration, soil erosion control and benefit: cost ratio in maize (Zea mays L)/cowpea (Vigna sinensis L.) based cropping systems under minimum tillage (MT). All crops recorded higher grain yields in the plots under higher (120 kg K₂Oha⁻¹) K application than the ones under recommended K (40 kg K₂Oha⁻¹). The five years’ mean yield data showed that the plots under higher K application produced 16% more maize equivalent yield than the recommended doses. Plots under cowpea based rotation yielded 14% higher crop productivity than the plots with maize based rotation. The added effects of higher K application in kharif (rainy season) crops also showed a significant enhancement in yield of winter crops [wheat (Triticum aestivum L.), lentil (Lens esculentum Medicus.) and mustard (Brassica juncea L.) and the maximum enhancement was found in the plots under cowpea-mustard rotation. Relationship between yield and sustainable yield indices revealed that only agronomic efficiency of mineral fertilizer input was significantly correlated with grain yield. Similarly, higher doses of K application not only increased the water use efficiency (WUE) of all the crops but also reduced runoff and soil loss by 17 and 16% under maize and by 23 and 20% under cowpea cover, respectively. On an average, 17% of left over carbon input contributed to soil organic carbon (SOC). Further, plots under cowpea based rotation with higher doses of K application recorded increased SOC contents. Over five years, the K balance coefficient for the plots under recommended rate was 0.67, indicating that more K was removed than applied. At the higher rate, the average K balance coefficient recorded was 1.29. Net return was also increased with the application of higher doses of K than recommended K and the trend was similar to that of grain yield. Thus, the present study demonstrates several beneficial effects of higher annual K application than the recommended dose to all crop rotations (especially to cowpea-mustard rotation), hence, the same is advocated for adoption by the farmers in this part of the country.