Summary of research project: |
Objective and technical fields:
Improvement of water use and raising the efficiency of mineral fertilizers application through optimization of winter wheat irrigation regime.
Objectives: elaboration of the optimal water and nutrient regime for winter wheat guaranteeing sustainable, maximum and profitable yield and rational use of irrigation water and fertilizers under the conditions of low-mountain Northern Tadjikistan. Planning and control of the water-nutrient regime for wheat and raising the productivity of irrigated lands under the conditions of water scarcity.
Scientific and technical approach:
Study of water-physical and agrochemical properties of the plot, soil moisture dynamics, regime of irrigation and nutrition, growth, development and productivity of winter wheat on the basis of field experiments and laboratorial studies. The goal of the studies is elaboration of the scientifically grounded recommendation on the water-nutrient regime for wheat, improvement of planning and control of water use, raising the productivity of irrigated lands under the conditions of scarcity of water and financial-technical resources.
Environment characteristics:
Absolute maximum temperature is +25oC and +42 0Ñ, absolute minimum temperature is -34oC and -29oC. In the highlands cereals can ripe before the height of 2800-2900 m. Duration of the cold period is 95-240 days, duration of the real winter is 30-180 days. The experimental plot is located at the height of 1350-1400 m above sea level. Annual precipitation is 372-440 mm. Maximum precipitation falls in April-May, minimum precipitation falls in August-September. Amount of days with snow cover is 57-183 days, snow cover depth is 9-31 cm. Average relative air humidity is 56,5%. Average wind speed is 1,6-4,7 m/sec., maximum wind speed varies from 16-17 to 29-34 m/sec. Relief is gullied. Soils are mostly gray, from bright to typical. In the south of Shakhristan sink ground waters are formed, where hydrocarbonates predominate. In the central and northern parts sulphate percentage is higher, total salinity is 0,1-0,7 g/l, more seldom it is 0,9 g/l. Soils of the plot are medium loam, volume weight of 0-100 cm layer is 1,34 g/cm3, specific weight is 2,72 g/cm3, porosity is 50,8%, minimum moisture capacity is 22,9% of the mass of absolutely dry soil. Inclination is 0,0015.
Parameters of Pilot Projects and Technical Solutions:
The area of the experimental plot was 2,0 ha. It consisted of 20 fields. The area of each field was up to 500 m2, land use efficiency was 0,92. Irrigation was made through furrows of the surface earthen network, canal efficiency was 0,85-0,90. Length of irrigation furrows was 100 m. The plot had a quadrangular form with an internal flume canal on the right side.
Irrigation norms, depth of irrigation and irrigation schedule were determined by a given regime of preirrigation soil moisture.
Methodology:
Field natural studies and observations on movement of moisture and nutrients in the soil, irrigation and fertilizing regime, growth, development and productivity of winter wheat were carried out. The plot was provided with necessary measuring and accounting equipment. The following variants were compared: (a) On irrigation regime - irrigation according to agrarian recommendations; without vegetative irrigation; irrigation according to soil moisture equal to 60, 70 and 80% of the normal soil moisture; (b) On nutrient regime: applying phosphorous-potash fertilizers (P60K60) norms of nitric nutrition were studied (N0; N50; N100; N150 kg/ha). Depth of the studied soil layer during the period from sprouting till stalk shooting was 50 cm, further it was 70 cm. Systems analysis was used.
Results:
Typical feature of the plot was abundant precipitation in autumn and winter-spring periods. However, during the optimal period of winter wheat sowing precipitation was insufficient for sprouting. In connection with this fact experiments were carried out with a water supply irrigation with the norm of 900 m3/ha. Results of the studies showed that with raising the preirrigation soil moisture from 60% to 70% and 80% from the normal soil moisture, number of water gifts increased from 1 to 4, irrigation norm increased on the average from 783 to 2952 m3/ha. Ratio of the gross field irrigation norm to the net field irrigation norm varied from 1,29 to 1,36. Water losses under furrow irrigation were the following: surface release - 8-19%, deep release - 11-22%, evaporation was assumed as 10% of the depth of irrigation. It was discovered that irrigation according to soil moisture at the level of 70% and 80% of the normal soil moisture caused rise of grain yield by 1,12 and 1,13 t/ha comparing with the control variant. Under irrigation according to soil moisture irrigation water expenditures per unit of production were minimum - 434 and 500 m3/t. Applying mineral fertilizers N100P60K60 with raising the preirrigation soil moisture up to 70% of the normal soil moisture, grain yield rose from 3,32 to 4,82 t/ha; as a result of further raising of moisture up to 80% of the normal soil moisture grain yield rose only by 0,01 t/ha comparing with the variant of 70% of the normal soil moisture.
Raising the dose of nitric fertilizers up to 100 kg/ha led to the rise of grain yield from 1,90 to 3,32 (variant «water supply irrigation») and 2,78 - 4,82 t/ha (variant - 70% of the normal soil moisture). Further raising the dose of mineral fertilizers up to N100P60K60 did not lead to the rise of the grain yield. On the basis of obtained data for optimization of the water-nutrient regime for winter wheat contour-graphic method for analysis of a multiparameter experiment was elaborated which allowed to determine and visually show the best results, determine influence of each parameter (X1 - irrigation and X2 - fertilizers application) on Y function (grain yield) and obtain the mathematical model of the process. Thus, it was determined that the most optimal and profitable irrigation regime for winter wheat is irrigation according to soil moisture (70 +/- 3% of the normal soil moisture) with rational norms of mineral fertilizers: N100P60K60. Under this regime grain yield was 4,5-5 t/ha. This yield was obtained by 2-4 vegetation water gifts with a water supply irrigation. It was found that bioclimatic coefficient (ration of a net irrigation norm to water balance deficit) which served for determination of the irrigation norm, varied from 0 to 0,29 (April-September) and from 0 to 0,44 (October-August). Relation between the grain yield and bioclimatic coefficient was found. Results of studying the total water consumption by the water balance method for 0-100 cm soil layer showed that the main income was autumn-spring precipitation and irrigation water. Depending on the irrigation regime irrigation norm in water balance varied from 18,8 to 48,8%. In the optimal irrigation variant (70% of the normal soil moisture) irrigation norm was on the average 42,8%, soil storage moisture was 10,6%, precipitation was 46,6% (coefficient of precipitation use was m=1) of the total water consumption. Depending on irrigation regimes winter wheat water requirements varied from 4162 to 6046 m3/ha. With the optimal water provision of crops (70% of the normal soil moisture) average daily water requirements varied: sprouting - tillering - 8,5 m3/ha; tillering - stalk shooting - 15,0 m3/ha; stalk shooting - ear formation - 24,4 m3/ha; ear formation - blooming - 49,2 m3/ha; blooming - milk ripeness - 38,4 m3/ha; milk ripeness - wax ripeness - 23,9 m3/ha; wax ripeness - full ripeness - 16,4 m3/ha. For the growing period water requirements were 19,1 m3/ha. Relation between grain yield and wheat water requirements was found. The relation is curvilinear with the coefficient of correlation relation equal to 0,94 +/- 0,1. Area of introduction of the development was 1195 ha. On the average 21,4% of irrigation water was saved. Profitability was 148,6 ruble/ha (in prices before 1990).
|
