A study of basal crop coefficient for wheat under humid regime from heat unit accumulations

A methodology has been presented to compute basal crop coefficient from soil moisture and heat unit accumulations, for wheat in the humid region of northeast India. In developing the method data from 1976-77 to 1981-82 crop seasons for the Sonalika variety of wheat from germination to maturity have been used and tested on independent data set for 1982-83 and 1985-86 crop seasons. Milk stage to physiological maturity stage is found to use maximum fraction of heat unit totals. The largest value of basal crop coefficient is about I 5 occurring during milk stage of the crop growth. Very high correlation is noticed between the actual ET and those computed from the model.

Requirement of heat unit and agrometeorological indices in selected wheat growing zones

Wheat growing ET -stations (viz., Jorhat, Varanasi, New Delhi, Ludhiana, Raipur, Jabalpur, Akola, Bellary, Banswara and Jodhpur) situated in arid to per humid climatic zones were selected. Heat unit and three agromeleorological indices, viz., ARI (agroclimatic rainfall index), YMI (yield moisture index) and AI (aridity index) were computed at various growth stages of wheat crop using latest available five years data for each of the stations. The study revealed that the crop degree days requirement varied from 1580 (at Jorhat) to 2350 (at Akola) with the maximum requirement at tillering and milk stages. All the stations (except Jorhat) recorded ARI values less than 25%, while for the stations in peninsular and western India, the values were even below 10%. Low cumulative YMI values were obtained in peninsular and western India, while high values were observed over eastern India. The wheat crop did not experience any aridity during tillering to flowering stages for all the stations (except Bellary and Banswara). High values of At were observed at early and late crop growth stages. Negative correlation was obtained between AI and ARI with the highest value (-0.89) observed at New Delhi. Depending upon this study, the wheat growing areas were divided into five zones.

Evapotranspiration and heat unit requirement of cowpea

Weighing gravimetric lysimeters are used to measure actual evapotranspiration of cowpea for an experiment conducted for two years during Kharif 2004 and 2005. A multiple regression equation has been generated for relating crop coefficient of cowpea with week after sowing. The highest value of crop co-efficient was found to be 1.015 on 6th week after sowing under Bangalore climate, the average values of actual evapotranspiration from cowpea crop and heat unit requirements over a period of 89 days in the Kharif season are found to be 284.8 mm and 1293 degree days respectively.

Crop specific requirement of growing degree days and agrometeorological indices in rice growing zones

The spatial and temporal distributions of heat unit and various agrometeorological indices for the rice crop, are studied in this paper. Eight ET – stations were selected from six rice growing zones, viz., Canning (in lower Gangetic plains), Bikramganj and Varanasi (in middle Gangetic plains), Ludhiana (in trans Gangetic plains), Ranchi, Shymakhunta (in eastern plateau and hills), Annamalai Nagar (in east coast plains and hill region) and Pattambi (in western plains and ghat region). Eleven crop growth stages were identified for this study, viz., germination, nursery seedling, transplanting, tillering, active tillering, lag phase, panicle initiation, flowering, grain formation, grain maturity and harvesting, the duration of each of the growth stages varied widely, station wise. Daily data were collected growth stagewise for latest available five years and the mean values were computed for the derived parameters, viz., the crop requirements of heat unit, agroclimatic rainfall index (ARI), yield moisture index (YMI), aridity index (AI). The study revealed that for rice crop the total degree days requirement varied from 1706 degree – days (at Ranchi) to 2815 degree – days (at Shymakhunta). It showed primary peak (with 16.7 % of total requirement) at active tillering stage. The ARI values were mostly higher than 100 per cent. The mean YMI values varied widely from 477 mm (at Bikramganj) to 1523 mm (at Pattambi). The values showed main peak at active tillering stage. The AI values showed moderate aridity at early growth stages, which increased at advanced crop growth stages.

Water and heat unit requirement in different growth stages of Soybean (Glycine max L. Merrill) at Bhopal

In this study, ET data available on Soybean crop for Bhopal during 1991-95 have been utilized. With regard to water need of the crop, the life span of soybean has been divided into five important growth stages viz., seedling up to 2 weeks after sowing (WAS), vegetative (3-8 WAS), flowering (9-10 WAS), pod development (11-13 WAS), and maturity (14-15 WAS). In this paper, consumptive use of water (ET), Water Use Efficiency (WUE), Heat Units (HU), Heat Use Efficiency (HUE) and crop coefficient (Kc) for different growth stages of the crop have been computed and discussed. The study revealed that on an average, Soybean crop consumed about 450 mm of water. The average WUE was found to be 3.23 kg /ha/mm. It was also observed that WUE does not depend only on the total amount of water consumed by the crop but also indicates the importance of its distribution during various growth stages. On an average, the crop consumed nearly 7%, 36%, 24%, 25% and 8% of water during seedling, vegetative, flowering, pod development and maturity stage respectively. The crop consumed maximum amount of water during vegetative stage. However, the average weekly ET rate was found to be highest during flowering stage (nearly 52 mm). Average heat unit requirement of soybean was found to be 1694 degree-days. Maximum heat units were required during vegetative stage (638 degree days) followed by pod development stage (358 degree days). The average HUE was found to be 0.86 kg/ha/degree days. Crop coefficient (Kc) values varied in the range 0.30 – 0.45, 0.55 – 0.90, 1.00 – 1.15, 0.85 – 0.70 and 0.55 – 0.40 during seedling, vegetative, flowering, pod development and maturity stage respectively. The crop coefficient values attained the peak during the flowering stage.

Maize seedling emergence in response to climatic variability in a tropical rainforest area

<p>Environmental factors causing low seedling emergence often observed in tropical maize (Zea mays L.) are poorly documented. This study was conducted to investigate the effects of weather factors on maize seedling emergence at the Obafemi Awolowo University Teaching and Research Farm (OAU TRF). Five maize varieties sown weekly, in 3-replicate RCBD experiments throughout the 2016 and 2017 cropping seasons, were used to monitor emergence percentage (E %), emergence index (EI) and emergence rate index (ERI). Climatic data were obtained from the automatic weather station located on the farm. Analysis of variance revealed highly significant (P ≤ 0.01) environmental effect for all traits. Soil moisture (Sm), relative humidity, air temperature, heat unit and soil heat flux (SHF) showed significant (P ≤ 0.05) correlation coefficients with all traits, but there was no relationship between the emergence traits and grain yield. Stepwise multiple regression and sequential path coefficient analyses indicated that increased Sm, rather than rainfall per se, increased the speed of emergence. Minimum air temperature and SHF with direct effects, and heat unit with indirect effect, negatively affected emergence the most. Relatively low Tmin and SHF, along with just enough Sm maximized seedling emergence in the rainforest agro-ecology of southwestern Nigeria.</p>