Effects of irrigation and straw mulch on water use and tuber yield of potato in eastern India

Potato, being a temperate crop, its growth and tuber production are limited by high atmospheric temperatures (mean temperature >17 °C). As a result potato is grown in winter season only (November-March) in the eastern plain of India when temperature is favourable. But during winter season, rainfall is erratic and meagre, therefore, potato crop in the region can only be grown with supplemental irrigation. In this study, potato crop was grown with four phenology based irrigation treatments (75 mm water depth with each irrigation) with three replications. Straw mulch at a rate of 6 t ha-1 was applied during the first earthing up in half of the plots to observe the variation of plant growth, water use efficiency and tuber production between mulched and non-mulched plots. The experimental split-plot design consisted of irrigation treatments in the main plots with mulching and non-mulching as subplots. Two years of pooled data with four irrigations resulted in air-dry tuber yields of 14.9 and 11.2 t ha-1 for the mulched and non-mulched plots, respectively. Significantly (p < 0.05) higher leaf area index, water use efficiency and intercepted photosynthetically active radiation (IPAR) were recorded in the mulched plots compared to the non-mulched plots under the same irrigation treatment. Higher yield and better crop growth were observed in the mulched plots, which might be due to conservation of soil moisture and reduction of soil temperature by 4-6 °C. The highest PAR (89% of the PAR incident above the crop canopy) was found near the crop with mulching and four irrigations. The 77-103 mm less depleted soil moisture in the different treatments was due to the application of straw mulch. Application of straw mulch significantly increased the available phosphorus and potassium in the soil. Water use efficiency and tuber productions differed significantly among irrigation treatments in the non-mulched plots but they did not in the mulched plots with three and four irrigations. Therefore, three irrigations of 75 mm each and mulching were recommended for growing potato in the region when limited water was available.