PHOTOSYNTHETIC ACTIVITY OF SWEET SORGHUM IN DIFFERENT OPTIMIZATION WAYS OF HYDROREGIME

Abstract

The aim of the research is to identify the optimization of the irrigation regime and the depth of wetting of the meadow-chestnut light clay soil when growing sugar sorghum in the foothill zone of Dagestan. The studies were conducted in a two-factor field experiment in the SEC “Khalimbekulsky” of the Buinaksk district. Records, observations and analyzes were carried out in accordance with existing recommendations. It was established that the maximum leaf surface area (36.6, thousand m 2 / ha), FPP (0.60 ppm / ha day) and ChFF (3.86 gm2 / ha day) and the utilization ratio of PAR (1.71) sorghum sugar obtained by the appointment of irrigation at the lower threshold of soil moisture in the layer 0 ... 0.4 m 80 ... 85% HB and exceed the figures at a deeper threshold of pre-irrigation moisture and soil moisture by 5.2 thousand m 2 / ha, 0.08 million m 2 / ha day and 0.71 ppm / ha day. Reducing threshold of pre-irrigation soil moisture to 70…75% of normal field capacity also reduces net productivity of photosynthesis on average in depth of humidification by 0.19 g / m² per day. However, even in the case with of soil humidification depth of 0.6 m it is indicator decreases more (by 18.6%) than when it is wetted by 0.4 m (by 4.9%). High photosynthetic productivity is explained by more favorable hydrophysical soil indicators, which caused by more frequent irrigation with relatively low humidification soil depth, excluding water stagnation on its surface and sowings damping-off after vegetative irrigations. Fodder grasses are highly productive of photosynthesis. For them the possible PAR utilization factor is 2.30…2.34%. In our studies growing season of Sweet Sorghum (from seedlings until the grain milk-wax stage of ripeness) varied over the years from 110 to 114 days. During this period is supplied 25.7 kcal PAR per 1 cm².