Dryland wheat is raised on stored water and limited precipitation. Nitrogen is known to increase grain yield and water use efficiency. But the crop response to N in relation to stored water, effect of N on water extracttion, effect of stored water and rainfall on water use are not sufficiently understood. Field experiments were conducted for a 3‐year period on clay loam (Haplustaff) and loamy sand (Ustifluvent) soils using four rates of N viz. 0, 40, 80 and 120 kg N/ha to probe the above aspects in two‐gene dwarf dryland winter wheat. Stored available water varied from 133 mm in a 180 cm profile to 204 mm in 120 cm profile and the rainfall varied from 62 to 141 mm. Maximum grain yields and response to N application increased with increasing water storage irrespective of growing season rainfall. Compared with a control, N application increased yield, water use, and water use efficiency under all situations. Differences in water use and water extraction pattern by unfertilized and fertilized wheat were small during early stages. But after 80 days, 80 kg N/ha increased water depletion from 60 to 180 cm layer by 25 to 300%. Under comparable rainfall, 52 mm higher initial available‐water storage in clay loam than in loamy sand, caused 90 mm greater water depletion from 180 cm profile. With adequate moisture in the lower layers, a heavy rain during tillering followed by a long dry spell induced deeper rooting which depleted all the available water from 180 cm profile.

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In dryland areas, where rains recede much earlier than the time of sowing of crops, moisture in the seed zone becomes limiting for stand establishment. Mulches are known to conserve moisture in the upper soil layers, so we studied the effect of mulching a standing maize or fallow on the yield of the maize and on following wheat. Mulching maize with green twigs of'basooti' a few weeks before harvest increased its yield by 16%. Both in maize and on fallow mulching increased water storage, particularly in the upper soil layers, and increased wheat yields from 19.0 to 22.5 q/ha after maize and 29.1 to 33.3 q/ha after fallow. It also led to increased water use and water use efficiency of wheat.As in many other areas, dryland wheat is grown in sub-montanous Punjab on water stored after fallow or on residual moisture left in the profile after harvesting the preceding monsoon season (kharif) crop. There is relatively little rainfall during the growing season of the crop and withdrawal of the monsoon (which is a characteristic of the area) results in the upper soil layers, and particularly the seed zone, drying out by the time wheat should be sown. Conditions are more adverse when wheat is sown after a kharif crop than after fallow, and both the total amount of residual or stored moisture in the profile and moisture in the seed zone limit the achievement of optimum yield.To ensure proper germination it is necessary to conserve adequate moisture in the seed zone, and organic mulches of crop residues are known to increase soil moisture storage (Greb et al., 1970) and maintain a higher water content in the upper few centimetres of the soil (Army et al., 1961). Even small differences in water content of the seed zone caused by mulching may have a considerable effect on the yield of wheat, whilst the better overall moisture regime resulting from mulching may also affect the yield of the kharif crop itself. We therefore conducted a 3-year study on the effect of organic mulch on the soil moisture regime and yield of kharif (summer) maize and the following crop of winter wheat, when the mulch was applied a few weeks before sowing the wheat, either in the standing kharif crop or on a fallow. MATERIALS AND METHODSField experiments were conducted from 1972 to 1975 on a non-saline, well-drained, deep, loamy sand to sandy loam soil of pH 8-o. Water retention at 1/10 bar suction in different layers varied from 9-5 to 20-5% and at 15 bar from 3-4 to 5-6% on an oven-dry weight basis. The bulk density of soil clods determined by the saturation 9 0014-4797/79/0000-1351 $01.00

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