Thesis for the Candidate of the agricultural science academic degree, specialty 06.01.02 – agricultural melioration (agricultural sciences) – Institute of Water Problems and Land Reclamation of NAAS, Kyiv, 2021.
The thesis presents the scientific substantiation of the methods of irrigation of soybeans and corn in the conditions of the Steppe of Ukraine at their cultivation in the chain rotation.
The experimental part of the research was carried out in 2018-2020 on the lands of the Kamyansʼko-Dniprovska research station of IWPaLM NAAS.
The formation of the water regime of the soil, the processes of evapotranspiration, and the productivity of crops were investigated depending on the methods of irrigation: sprinkler irrigation, drip irrigation with the ground-based laying of irrigation pipelines, and subsurface drip irrigation with laying of irrigation pipelines to a depth of 25 cm. The option without irrigation was a conditional control.
Comprehensive assessment and scientific evaluation of the effectiveness of soy and corn irrigation methods at their cultivation in crop rotation are the main scientific and applied results.
Based on the results of studies of the water regime of the soil, the actual parameters and features of the formation of irrigation regimes and the processes of plant evapotranspiration were established, and the statistical models «Water consumption-Yield» were built. Researched and established the patterns of growth and development of the plants, depending on the irrigation methods, soybean productivity indicators, and corn. It was found that the maximum levels of the yield of soybeans and corn were obtained with drip irrigation – 5,87 t/ha and 20,69 t/ha, respectively, while with subsurface irrigation, a significant decrease in yield was obtained – 4,14 t/ha of soybeans and 16,44 t/ha of corn. As for sprinkling, the decrease in yield by 0,22 t/ha and 0,62 t/ha compared to subsurface irrigation was within the margin of error of the field experiment (MEFE0,5 = 0,49 and 1,93). Without irrigation the lowest levels of crop's yields were obtained, – 1,38 t/ha of soybeans and 3,85 t/ha of corn.
The adaptation of the calculation method «Penman-Monteith» on soybean for irrigation conditions by sprinkling was tested and performed. It was found that in the initial and final phases of soybean plant development, the recommended Kc (FAO) overestimates the actual values of ETс to 42,8 %, and in the middle of the growing season, on the contrary, underestimates by 4,2-11,5 %. Therefore, for the practical use of the method, the correction of the culture coefficients Kc under the climatic conditions of the Steppe is a necessary condition.
Peculiarities of formation of zones of moistening of an average loamy soil under subsurface drip irrigation have been investigated; their geometric parameters have been established depending on the duration of irrigation.
Calculations justified the economic and energy efficiency of the various methods of irrigation of soybeans and corn's introduction.
Keywords: drip irrigation, subsurface drip irrigation, sprinkling, irrigation rate, irrigation regime, evapotranspiration, soybean, corn, productivity
