Summary of research project: |
Objective and technical fields:
Water use improvement through optimization of irrigation schedule and determination of fodder beet water requirements.
Development of biologically optimal irrigation schedule for fodder beet, which provides maximum, qualitative and cost-effective yield, efficient use of water, land and other resources under conditions of Central Tajikistan.
Scientific and technical approach:
To increase an efficiency in use of water and other resources a study of irrigation schedule, evapotranspiration, water balance and productivity of fodder beet is to be conducted. Importance of the study consists in improvement of water use planning, management and scientifically grounded recommendations on optimization of irrigation schedule for fodder beet and increase of irrigated land productivity.
Environment characteristics:
The plot is located in Hissar valley, 641-1215 m above sea level. Climate of the valley is characterized by the data from five meteorological stations. Maximum air temperature is 43-44 oC (in July), minimum is -24-30 oC. Average annual temperature is 14,1-15,1 oC, sum of positive temperatures (more than 10 oC) is 2192-2510 oC. Average annual relative air humidity is 46-53%, in summer - 31-42%. Evaporativity varies from 1311 to 1680 mm. Here north and north-east wind prevails, mainly during growing period. Average annual wind speed is 1,5-2,8 m/sec. There are rocky, brown, calcareous, dark gray, meadow-gray and, in small areas, meadow-bog soils. Area, where ground waters level is at 1,5-3 m, is 6624 ha or 11,2% of total one. Ground waters are, mainly, fresh (up to 1g/l) or slightly-salinized (1-3 g/l by solid residue). Soil texture - middle loam. Volume mass of 0-100 cm layer is 1,34 g/cm3, specific mass is 2,66 g/cm3 , porosity is 49,6 %, minimum soil moisture is 22,2% of dry soil mass. Permeability of 1 m layer varies from 9 to 24 mm/hour. Slopes of the surface are mainly 0,015-0,035, rarely 0,002-0,008. Source of irrigation is Big Hissar Canal (BHC), salinity of water is no more than 0,7 g/l.
Parameters of Pilot Projects and Technical Solutions:
Irrigated area of the pilot plot is 1,5 ha. The plot consists of 20 lots. Area of each lot is 240 m2. Each lot consists of 8 rows, land use efficiency is 0,91. Water is supplied through furrows from open earthen network. Efficiency of canals is 0,85-0,90, specific length of permanent canals is 60 m/ha, capacity is 200-350 l/sec. Length of irrigation furrow is 100 m, slope is 0,01.
Methodology:
Studies and observations of soil moisture, dates and depth of irrigation, water balance’s elements, evapotranspiration, growth, development and productivity of fodder beet. The pilot plot was equipped with meters to keep regular observations. Accountings and observations were conducted according to SoyuzNIKHI (1973) and VNIIK (1980) methods.
Results:
In order to develop an optimal irrigation schedule of fodder beet (sort “Akkendorf yellow”) 4 irrigation alternatives were compared: 1st one - “farm watering” (control); 2,3 and 4th one - initial soil moisture is 60, 70 and 80% respectively. Conducted studies showed, that in 1st alternative (watering according to plan and schedule adopted in the farm) 6 waterings were done during growing period of beet by the scheme 2-2-2 with big depth of irrigation. Here irrigation norm accounted for, on the average, 7280 m3/ha. When water was supplied under 60% of normal moisture, there were 4 waterings, irrigation norm was 4685 m3/ha. In 3rd and 4th alternatives 7 and 11 waterings were done respectively. Irrigation norm was 5734 and 6444 m3/ha respectively. Study on soil moisture dynamics during growing period of beet allowed to determine relationship between soil moisture and concentration of cellular sap (CCS) of beet leaves, which is used for irrigation timing. An optimal initial soil moisture for fodder beet was determined as 70-70-70% of normal moisture. Under such conditions, CCS of beet leaves within the growth stages must be at the following levels: 5,9% from sprouting till mass leaf formation; 7,2% from leaf formation till intensive root growth; 8,5% of dry matter from intensive root growth till cropping maturity. It is determined, that depending on irrigation schedule the depth of roots at the end of growing period varies from 140 cm (waterings under 80% of normal moisture) to 230 cm (without waterings). Air-dried mass of roots varies from 1,67 t/ha (without waterings) to 8,37 t/ha or 98,8% g/plant (waterings under 80% of normal moisture). Phenological observations showed, that duration of a phase from sprouting till leaf formation was 85-94 days, 148-152 days - till intensive root growth, 182-188 days - till full maturity. Maximum area of leaves in 10-20 July was, depending on irrigation schedule, 3325-7546 cm2 per one plant. Quantity of leaves was 28-43. Crop density accounted for, on the average, 84-86 Th./ha, photosynthetic capacity of crops varied from 3,2 to 7,2 mln.mg/ days. Dry biomass of roots at the end of growing period, depending on irrigation schedule, accounted for 47,6 g/plant (without waterings) and 219,5 g/plant (waterings under 80% of normal moisture). Different irrigation schedules affected considerably the yield formation of beet roots: 26,7 t/ha with no waterings, 105,9 t/ha of roots under “farm watering”, waterings under 60, 70 and 80% of normal moisture provided 97,9 , 154,1 and 156,2 t/ha respectively.
Ratio of beet roots’ yield to root mass varies from 14,9 to 19,4.
Study of total crop requirements of fodder beet using water balance method showed, that the main income item was irrigation water, which, on the average, accounted for 64-74%. Portion of water extracted from the soil store at 0-200 cm is 3-8%, portion of precipitation is 21-28%. Depending on irrigation schedules, the total crop requirements of beet varies from 7318 to 9906 m3/ha. The higher initial soil moisture the higher total crop requirements and portion of irrigation water in water balance, the lower portion of water extracted from the soil store.
To calculate total crop requirements bioclimatic coefficients of evaporation (ratio of total crop requirements to evaporativity) were determined. Bioclimatic coefficient in 1st alternative was 0,97, for 2,3 and 4th irrigation alternatives - 0,72, 0,80 and 0,86 respectively.
There is relationship between the yield of beet roots and initial soil moisture. The relationship is curvilinear, expressed by quadratic equation. Correlation is 0,89..0,06. Yield of beet roots increases from 85 to 170 t/ha while raising soil moisture within 60-80% of normal moisture. The maximum yield is formed under 70+2% soil moisture.
As a result of studies it is determined, that biologically optimal and cost-effective irrigation schedule for fodder beet under conditions of dark gray soils of Hissar valley is watering when the soil moisture is 70% of normal moisture during the whole growing period. It will require 7 waterings according to the scheme 2-4-1, irrigation norm will be 57000 m3/ha. Under such conditions 150-160 t/ha of beet roots and 18-20 t/ha of beet tops are obtained.
Irrigation water saving with respect to “farm watering” is 21,2%.
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