Answer:

When we heat air, the molecules jiggle and zip around faster, which causes them to spread out. When a mass of air takes up more space, it has a lower density. ... Warm air rises when it's surrounded by cold air because of its lower density.

aestivum L.)

Author links open overlay panelEl-Sayed E.A.El-Sobky

https://doi.org/10.1016/j.aoas.2017.05.007

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Abstract

This investigation was carried out in the Experimental Farm at Ghazala Village (Faculty of Agriculture, Zagazig University, Egypt) during two successive seasons (2014/2015 and 2015/2016) to study the effect of rice straw burning (rice straw plowing down and rice straw burning), phosphorus (P) level (0 and 15.5 kg P2O5/fad [fad = faddan = 4200 m2 and ha = 2.38 fad]), and nitrogen (N) level (30, 60 and 90 kg N/fad) on wheat (Triticum aestivum L. cv. Gemmiza 11). Burned rice straw significantly decreased the flag leaf area, spikes number/m2, 1000-grain weight, grain and total yields/fad. The increase of P level to 15.5 kg P2O5/fad produced significant increase in plant height, flag leaf area, grain weight per spike, 1000-grain weight but, decreased the number of spikes/m2 and the grain yield/fad and harvest index. The increase of N level up to 90 kg N/fad gave significant increase in grain yield and yield attributes except the number of sterile spikeletes/spike and 1000-grain weight which were decreased.