Objectives: to develop the optimal water saving technology for subsoil irrigation of cotton, which provides uniform moistening, favorable reclamation state of lands, reduced water consumption per unit produced, high cotton yields; to determine the effectiveness of the subsoil irrigation for cotton and the system efficiency.
Natural and economic conditions of the plot are typical for the Colodnaya steppe. Relief of the plot is smooth. Soils are gray-meadow, non-saline and slightly saline in some places. Soil texture shows light and medium light loam with fine interlayers of heavy loam, gypsum and carbonate.
Water table is 2,7-3,0 m. Groundwater is low saline (up to 4 g/l of soil residue).
Subsoil irrigation system is constructed within area of 120 ha (net) and connected with typical flume network. It consists of subsoil pipeline network. Watering tubes are perforated. Diameter of perforation holes is 2-2,5 mm and distance between them is 0,1 m. Depth of distributive tubes is 0,6 m, while it is 0,45 m for watering tubes. Subsoil irrigation system is equipped with regulation devices and gate-drossels. Field drainage is absent.
This plot was compared with the control plot under furrow irrigation.
The research determined the following optimal subsoil irrigation schedule: 4 irrigations by duty of 1,0-1,2 thousands m3/ha and irrigation norm of 4,2-4,5 thousands m3/ha; dates of irrigation - the end of May, the beginning and second half of July, second ten-days period of August.
On furrow irrigation plot irrigation norm was respectively 5,5-5,8 thousands m3/ha.
Cotton yield under subsoil irrigation was 4,25-4,57 t/ha, while it was 3,06-3,13 t/ha under furrow irrigation.
Water saving reached 20-25%, while yield increased by 1,0-1,5 t/ha.
Water balances were calculated for both compared irrigation methods followed by recommendations on subsoil irrigation technique and technology.
Disadvantages of the experiment:
- difficult wetting of top layer during first irrigation under conditions of dry spring;
- siltation of watering tubes.
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