Reprint - Central Arid Zone Research Institute

when sown early during the 25th week under Jodhpur conditions.The crop is vulnerable to drought with 78 per cent probabilitymostly during the reproductive stage when sown during 29th to 31stweek. The crop is more vulnerable to drought during the grandgrowth stage when sown during 27th week contrary to vulnerabilityduring reproductive stage of growth when sown in 26th week.30 Ramakrishna, Y.S., Singh, R.P. and Singh, K.C. (1982)Influence of systems of planting pearl millet on crop micro-climate.Annals of Arid Zone. 21: 171-179It was revealed that the crop canopy in the triple and paired rowsystems absorbed 3.6 and 2.0 times more radiant energy,respectively, than the uniform system of planting. The albedo of thecrop canopy remained almost the same throughout flowering andgrain formation stages, irrespective of the systems of planting.Lower values of vapour pressure deficit (VPD) and canopytemperatures, obtained during most of the day period in the tripleand paired row systems of planting, and lower ratios ofRn(G) / Rn(T), led to lower ET demand and improved crop yields ofthe order of 7.7 to 15.0%.31 Ramakrishna, Y.S., Rao, A.S., Singh, R.S., Kar, A. and Singh,S. (1990)Moisture, thermal and wind measurements over two selected stableand unstable sand dunes in the Indian desert. Journal of AridEnvironments. 19: 25-38Studies on the morphology, thermal, moisture and wind regimeacross a barchan and a parabolic dune in the Indian desert indicatea higher summer air temperature and a higher annual diurnalrange over the barchan than over the parabolic dune, due tovegetation cover over the latter. Vegetation was also responsible for30% less moisture over the parabolic dune than over the barchanduring the rainy season. Direction and rate of movement of sandacross the dunes changed with the direction of peak winds andgusts. A curvilinear relationship has been established between meandaily wind speed and sand movement over the barchan. The longerduration of turbulent wind at the barchan crest, compared with thaton the parabolic dune crest was a major factor influencing sandmovement from the former compared with the latter. The barchanmoved 7.0 m during a one year cycle, while the parabolic crestmoved 0.5 m.32 Ramakrishna, Y.S., Sastri, A.S.R.A.S., Rao, G.G.S.N. andRamana Rao, B.V. (1984)