Grain yield and water use efficiency of wheat (Triticum aestivum L.) in relation to irrigation levels and rice straw mulching in North West India

Continuous cultivation with a rice (Oryza sativa L.)–wheat cropping system in north-western India has led to an irrigation water crisis due to excessive withdrawal of underground water. Large scale on-farm burning of surplus rice residue by the farmers has also caused intense air pollution. Retaining rice residue as surface mulch as an alternative to burning could be useful for soil moisture conservation, reducing air pollution and improving soil organic matter level. A field experiment was conducted for three years (2008–09, 2009–10 and 2010–11) to study the effect of four irrigation treatments with irrigations applied at critical growth stages and four rates of rice straw mulching on the grain yield and water use efficiency of wheat in North-west India. The irrigation treatments were irrigations at crown root initiation (CRI) and boot stage (I2); CRI, tillering, and boot stage (I3); irrigations at CRI, tillering, boot stage, and milk stage (I4); and irrigations as CRI, tillering, jointing, boot stage, and milk stage (I5). Mulch application included no mulch (M0) and 2 (M2), 4 (M4), and 6 (M6) tha−1. Significant irrigation×mulch interaction effects were observed on grain yield during 2008–09. Rice straw mulching decreased the maximum soil temperature by 2.0–3.3°C recorded during the emergence of the wheat crop in different years. Mulching at different rates reduced the mean weed dry matter by 12.5–52.7% compared with the no mulch treatment, and increased growth and yield attributes of wheat crop in different years. Protein content decreased from 12.15–13.04% in the I2 treatment to 11.95–12.58% in the I5 treatment. Straw mulch at M6 decreased the water use from 2.1 to 2.9cm compared with the no mulch treatment in different years. Water use efficiency decreased with the increasing irrigation level but increased with mulching. WUE increased as mulching increased for the I2, I3, and I4 treatments, but not for the I5 treatment. The increase in water use efficiency with the I5 treatment compared to no mulch was observed at the M2 treatment only and no further increase occurred thereafter. After three years of experimentation straw mulching decreased soil bulk density and increased organic carbon content in the 0–15cm soil layer. It may be concluded from this study that under limited irrigation water conditions, rice straw mulching will be beneficial in increasing yield, soil organic carbon and water use efficiency in wheat.