Ranjodh Singh

Effect of N-rates on dryland wheat in relation to mulching previous crop or fallow

In many rainfed areas a rainy season crop is followed by a post rainy season (rabi) crop and the yield of the latter is directly related to the profile-stored water at the time of its sowing. Mulching is known to help increase soil moisture storage. The yields of dryland crops are also limited by availability of nutrients, particularly nitrogen. We studied the effect of organic mulching in rainy season maize or fallow on the yield of maize and the yield and water use efficiency (WUE) of the following wheat fertilized with different rates of N.Mulching increased yield of maize by 9–12% and that of the following wheat by 25–28%. The increase in wheat yield with mulching in the previous crop of maize is attributable to greater residual moisture after maize particularly in the seed-zone and enrichment of soil with nutrients. In wheat following mulched maize, the yields with 0 and 40 kg N ha−1 were comparable to those with 40 and 80 kg N ha−1 in the absence of mulch. For a given N rate the yield of wheat was a function of available water supply. The yield increased with water supply up to a certain level beyond which it decreased with additional water supply. The threshold water supply and the corresponding yield increased with increase in N rate. Favourable effects of mulching in maize on the yield of wheat decreased with increase in water supply. The results suggest that to achieve optimum yield of wheat in double cropping the previous crop should be mulched and the N rate for wheat should be chosen in relation to available water supplies.

Response of dryland wheat to small supplemental irrigation and fertilizer nitrogen in submontane Punjab

In northern India, the monsoon rains recede much earlier than the sowing time of post-rainy crops and the seed-zone gets dried. Excess rain water collected in near-farm or on-farm reservoirs permits small presowing and/or postsowing irrigation(s) to increase yield which is also limited by N supplies. Field experiments were conducted to match N application rates with available water supplies to optimise wheat (Triticum aestivum L.) yields. Five rates of fertilizer N (0, 25, 50, 75 and 100 kg ha−1) were combined with five irrigation treatments (no-irrigation; 5 cm and 10 cm presowing irrigation, 5 cm irrigation 30 days after sowing and; equal presowing and postsowing irrigations totalling 10 cm). The yield was regressed over crop water supply inclusive of irrigation (W) or exclusive of irrigation (W1) and applied nitrogen (N). Grain yield increased with increase in both water supply and N-rate. Within certain limits N and W1 substituted each other for yield and so did irrigation and W1. Irrespective of irrigation, the amount of N required to substitute for given W1 to maintain a given yield decreased with increasing W1. At low W1, irrigation substituted for small changes in W1 but with increased W1, irrigation substituted for larger changes in W1. Also with increase in N level given irrigation substituted for smaller amount of W1. These regressions permit recommendations of N in relation to stored water and seasonal rain with or without limited irrigation. The latter was most useful at intermediate W1.

Nitrogen response of maize under temporary flooding

The adverse effect of temporary flooding on maize (Zea mays L.) yields and the nitrogen management required to mitigate the effect of flooding were studied for five years in field experiments on Choa sandy loam soil.Maize yields decreased with increase in duration of flooding and with decrease in the age of the crop at the time of flooding. Flooding periods exceeding 48 hours caused significant crop damage. The loss in yield on account of flooding was, however, less in 40-day old crops. A 24 hours flooding decreased grain yield by 17.7 and 3.9 per cent in 20-day and 40-day old crops respectively. Maximum yield loss amounted to 1.23 t ha−1 of grains with 72 hours of flooding of 20-day old crop indicating that a younger crop is more prone to the deleterious effect of flooding.The nitrogen content of grains decreased significantly with increase in flooding period. A supplemental dose of 7 kg N ha−1 as urea spray significantly increased grain yield. Soil application of supplemental nitrogen at the rate of 14 or 20 kg N ha−1 enhanced the maize yield by 0.7 to 0.9 t ha−1 under temporary flooded conditions. Spraying with urea solution increased nitrogen removed by the crop.Successive increments of 60 kg N ha−1 gave an additional yields of 1.23, 1.01 and 0.41 t ha−1 over the crop that received no nitrogen. Flooded maize responded to even higher rates of N fertilization than the dose of 120 kg N ha−1 which is recommended in this region.

Response of dryland wheat to fertilizer nitrogen in relation to stored water, rainfall and residual farm yard manure

Yield response of dryland wheat to fertilizer N application in relation to components of seasonal water (available soil moisture and rainfall) and residual farm yard manure (FYM) was studied for five years (1983–84 to 1987–88) on a maize-wheat sequence on sandy loam soils in Hoshiarpur district of Punjab, India. Four rates of N viz. 0, 40, 60 and 80 kg ha−1 in wheat were superimposed on two residual FYM treatments viz. no FYM (F0) and 15 t ha−1 (F15) to preceding maize. FYM application to maize increased the residual NO3-N content by 19–30 kg ha−1 in the 180 cm soil profile. For a given moisture distribution, F15 increased attainable yields. Over the years, F15 increased wheat yield by 230 to 520 kg ha−1. Response to fertilizer N was lower in FYM amended plots than in unamended plots. Available soil moisture at wheat seeding and amount and distribution of rainfall during the vegetative and the reproductive phases of crop development affected N use efficiency by wheat. Available soil moisture at seeding alone accounted for 50% variation in yield. The residual effect of FYM on wheat yield could be accounted for by considering NO3-N in 180 cm soil profile at seeding. The NO3-N and available soil moisture at wheat seeding along with split rainfall for two main phases of crop development and fertilizer N accounted for 96% variation in wheat yield across years and FYM treatments.

Estimating Potato Tuber Yield in a Sub-tropical Environment with Simple Radiation-Based Models

Dry matter and tuber yields of potato grown in a sub-tropical environment were estimated employing simple radiation-based models which require meteorological information on air temperature and solar radiation. Two versions of the MacKerron and Waister (1985) model, in which estimation of dry matter accumulation relies on a single composite parameter, radiation use efficiency (RUE), were compared with the Versteeg and Van Keulen (1986) model, which explicitly accounts for temperature and radiation effects on dry matter accumulation. In the original version of the MacKerron and Waister model, a linear change in the radiation interception factor with leaf area index is assumed; in the modified version an exponential change in the interception factor with leaf area index is considered. The accumulation of dry matter estimated from all three models was close to the measured values throughout the growing season, but estimates of tuber yield differed widely. Our analysis showed that the best agreement with measured values was obtained using the MacKerron and Waister linear model with RUE values adjusted according to the incident radiation level

Effect of N fertilization on yield and moisture extraction by rainfed maize as affected by soil type and rainfall in Punjab, India

Abstract Field experiments were conducted in a sub-humid region of Northern India for a 3-year period on loamy sand (Ustifluvent) and sandy loam (Haplustalf) soils using four rates of N (0, 40, 80 and 120 kg/ha) to study their effect on yield and moisture extraction by rainfed maize. Seasonal rainfall varied from 477 to 861 mm. Grain yield and response to N application varied with soil type irrespective of seasonal rainfall. Response to N application was observed up to 40 and 80 kg N/ha in loamy sand and sandy loam soils, respectively. Compared with control, N application increased yield and water use in all situations. The fertilized crop used 23–49 mm more profile water than the unfertilized crop. The fertilized crop particularly utilized more water from lower layers (120–180 cm) during a low rainfall year.