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The favoured temperature range for soyabean seed germination is 25 -30 8C and the crop is sensitive to water stress. In northern India, the crop is sown in the hot-dry months of May -June. Straw mulching can alter the soil's hydrothermal regime by lowering the temperature and reducing evaporation losses. A field experiment was conducted from 1999 to 2002 at the Research Farm of Punjab Agricultural University, Ludhiana on a loamy sand soil to evaluate the effect of wheat straw mulch on soil temperature, soyabean seed yield and crop growth. Maximum soil temperatures at sowing depth, recorded during the 1-month period after sowing (seed germination to seedling establishment stage), were high under no-mulch, ranging from 30.6 to 48.6 8C, while mulching substantially reduced these temperatures by 1.4 to 12.7 8C. Mulching increased soyabean seed yield by 4.4 to 68.3% in different cropping seasons; it also increased plant biomass by 17 to 122% and nodule mass by 8 to 220%. Leaf area index, chlorophyll content of leaves and number of pods per plant were all increased. Seed yield improvement under mulch was negatively correlated with rainfall distribution (number of rainy days) and amount during the whole cropping season. The percentage increase in seed yield with mulching was regressed against the total number of rainy days and total rainfall in millimetres in the cropping season. Thereby 93% of the variation in response to mulching in different cropping seasons was explained by the distribution and amount of rainfall.

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Depleting water resources in many regions of the world and increasing fertilizer nitrogen (N) cost necessitate efficient resource use. This is crucial in shallow-rooted crops like potato due to a great probability of water and N loss. In Indian Punjab, autumn potato experiences high temperature at planting time that causes poor growth and tuber yield. Mulching with crop residues provides favorable soil hydrothermal conditions that may enhance yield and economize irrigation and N use. This study examined the combined effects of residue mulch, irrigation, and N regimes on potato productivity in two soils in a subtropical environment of north-west India. Treatments included combinations of two mulch rates (0 and 6 t ha −1 rice residues) in main plots, three irrigation regimes (irrigation water to pan evaporation ratio of 2.0, 1.4, and 0.8 in the sandy loam and 2.0, 1.5, and 1.0 in the loamy sand) in subplots and four N rates (0, 135, 180, and 225 kg ha −1 ) in sub-subplots with three replications. Potato was planted in the second week of October with recommended doses of P 2 O 5 and K 2 O and harvested in the last week of January. Tuber yield was higher in the sandy loam than in the loamy sand soil reflecting effects of available water capacity and inherent fertility. Mulching improved tuber yield by 22% on the sandy loam and by 31% on the loamy sand. Irrigation benefits were more in the sandy loam (20%) than in the loamy sand (14%). Nitrogen response was also greater in the sandy loam soil. Interactions between mulching and irrigation showed that yield gains from mulching were greater in less frequent irrigation regimes. For a given yield, mulching saved 90-100 mm of irrigation water. Mulching benefits were also greater at low N regimes, demonstrating a saving of 90 kg N ha −1 for a given yield. Mulching and N enhanced water productivity (WP), and these effects were greater in less frequent irrigations. Mulching effects on tuber yield, irrigation, and N economy are attributed to its effects on moderation of soil temperature and reduction in soil water evaporation.Potato Research

In northern India, chilli is transplanted in the hot and dry months of February and March when the crop depends upon irrigation water for canopy establishment. Hybrid chilli may require more irrigation water and fertilizer N due to its higher yield potential but the problem of the depleting groundwater table in the region necessitates developing a technique for reducing water requirement. Rice residue mulching can lower soil temperature and reduce evaporation losses from soil. An experiment was conducted on sandy loam soil for three years to evaluate the effect of rice straw mulch @ 6 Mg ha 71 on yield, fertilizer N and irrigation water requirement of hybrid chilli. Maximum and minimum soil temperatures at 50 mm depth during 2003 were lowered up to 8.9 and 2.28C, respectively, by rice residue mulching. Mulching improved fresh red chilli yield by 2.4 Mg ha 71 and required 120 mm less irrigation water. Substantial yield increase with mulching may be attributed to favourable soil hydrothermal regime as evident from lower soil temperature, higher profile moisture (12 mm) and 13.5 Mg ha 71 lower weed biomass. Chilli yield obtained with 45 kg N ha 71 with mulch was the same as that of 75 kg N ha 71 without mulch. Ascorbic acid content decreased with lower irrigation frequency but was significantly higher without mulch.