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Solar Pasture Irrigation



Solar water pump pasture irrigation system design, installation, operation and management.

In order to let the grass in the sample grassland have same growth speed, we did a test in the irrigation area and comparison area from 26th June to 16th Sep in 2011. The test is to measure the grassland community structure, the biomass on the surface earth, underground plant quantity, soil solid degrees and soil water content.
The test adopts single factor treatment (harvest period) with randomized field design, plot area is 1 x 1m2 with 5cm stubble height and 5 times repeat.

The solar pumping system installed in grass planting base of Qinghai Academy of Animal and Veterinary, utilizes Solartech PS370-2 system, consisting of 3600W solar array, PB750L solar pump inverter and 2kw motor power, the total lift is 40m with 8m3 water flow per hour.

3.Operation and Management
The installed system operated and managed by testers of Qinghai Science Institute of Animal Husbandry according to the system design and irrigation cycle.
Experiment data Collection in grass growing period: the working time of solar panel, irrigating frequency, number of irrigation group, time for each irrigation, irrigating quota and cycle.
A.Solar array operation time: six month in total
B.Irrigating frequency: 3-4times in pasture of the Yellow River Region
C.Formulation of irrigation regulation

a.Net water irrigating quota:
Calculation for net irrigating quota (M) of grass crops:
M=0.1γh (β1-β2 )/η
M - Irrigating quota (m3/Mu);
H - Planed wetness soil layer depth (cm), takes as 25 cm;
γ- Soil bulk density(g/cm3),takes as 1.35 g/cm3
β1- The upper limit of water content appropriated for soil , takes as 90% of the water holding capacity of the field.
β2-The lower limit of water content appropriated for soil , takes as 65% of the water holding capacity of the field. The water holding capacity for the field is 24%.
η-The effective utilization coefficients of sprinkling waterη=0.80
M=0.1×1.35×25×24×(0.90-0.65)/0.80≈25.3 m3/Mu
Or 30-40 m3/Mu ground irrigation for artificial pastures, 20-40 m3/Mu sprinkle irrigation; 20%—30% water increases for natural pastures.
The project adopts sprinkler hose irrigation for water conservation, so net water irrigating quota is 30 m3/Mu and 35 m3/Mu gross water irrigating quota.
According to the notice for water consumption quota in Qinghai province(【2009】No.62 document 3-3) issued by the People's Government of Qinghai Province.
The irrigating frequency for artificial pasture in Maqin County is 3-4 times and rated irrigating quota is 100-120 (m3/Mu), so the appropriate irrigating quota for this project is 35 m3/Mu and 3-4 times irrigating for grass growth period, total irrigating quota is 110 m3/Mu.
Calculation for irrigation cycle is as below:
T——Irrigation cycle
e——Crop maximum average daily water consumption
η——Utilization coefficient for spray water
In this project, Crop maximum average daily water consumption is 3.61mm/d with 25.3 m3/Mu (38.06 mm) irrigating quota, 0.8 utilization coefficient for spray water and 9 days of Irrigation cycle (T).

b.Confirmation of crop irrigation regulation
In this project, tiled micro-sprinkling hoses are adopted. Detailed capability parameters are showed in below table. According to the well depth and pump specification, the well outlet pressure is 0.7Mpa, the sprinkler hose in this project designs for 0.1Mpa with 2m spraying radius.  According to the calculation, 7 lines of sprinkler hoses are used for irrigation simultaneously. As this project utilizes solar pumping system, considered the variation of sun radiation intensity in a day, 4 lines of sprinkler hoses set as a group to irrigate simultaneously, sum up as 50 groups. 
The natural pasture gross irrigating quota is 70 m3/Mu, Four lines of sprinkler hoses can irrigate 1.2 Mu areas. According to the performance parameter table of sprinkler hose, water flow for 100m sprinkler hose is 10-13 m3/h, in this project; it is designed for 10 m3/h, and irrigates 1.2Mu areas with 43.6hours, 300hours needed to irrigates the whole 100Mu experiment areas.

D.Calculation of irrigating water consumption
Irrigating water consumption can be calculated directly as following formula for small scale of pasture with few species of crops:
W-Irrigating water consumption (m3)
A-Irrigating area (Mu)
M-General irrigating quota (m3/Mu)
Taking the irrigating area as 100Mu according to experiment area, the general irrigating quota is 110(m3/Mu), so the irrigating water consumption is110000 m3
Yield measurement (unit: kg/Mu)
Grass yield of irrigation area and comparison area in harvest time

                       Irrigation Area        Comparison Area
26th Jun             218.3                           131.1
6th July               257.4                           162.3
16th July             362.1                           296.2
26th July             372.7                           312.5
6th Aug               388.3                            326.1
16th Aug             413.2                            365.2
26th Aug             416.1                            375.4
6th Sep               388.4                            319.1
16th Sep             353.6                            321.8

Test Provides data of water consumption and grass yield by traditional irrigation (ground irrigation) and data of grass yield without irrigation, for comparison and analysis of solar pumping system irrigation.

The regular pattern of grass yield changes according to harvest time in irrigation area and comparison area.


Qinghai solar pasture pumping irrigation         The pasture irrigating by solar pumping system

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