Micro-sprinkler Irrigation of Orchard

Abstract

Analysis of the field measurements recorded provided information about the sprinkler system and its operation. The distribution characteristic (DC) of 66% indicated the pattern was uniform and that the drop-off in application rate at the outer perimeter was fairly rapid. A little higher value and steeper drop-off would be even better, since the overlap was small at the operating radius of 4.0 for the 7.0 m tree and sprinkler spacing. The current irrigation management program of 24-hour sets produced storage efficiency (SE) of 72%. This is quite low for orchard sprinklers, since 28% of the applied water would not be available for the trees. Of this, approximately 10% was lost to evaporation and/or possible inaccuracies in measurements. Leakage from the sprinkler was not measured and is not included in the 10%. The remaining 18% went too deep. This loss to deep percolation was caused by running the sprinkler 24 h, which was too long. The analysis showed that 19-hour sets would increase the SE to 89%. For the soil moisture depletion (SMD) of 10 cm, an average of about 8.4 cm was stored under the circular wetted area by the 24-hour set, but only 3.2 inches would be stored during a 19-hour set. Changing to a 19-hour set would theoretically require slightly more frequent (3%) irrigation, but would require only 79% as much water per irrigation. For the presently used sprinkler pattern, which wets only part of the soil, the average depth of 8.1 stored over the whole orchard area should be used for computations of irrigation frequency based on the evapotranspiration rate. For determining the SMD at which to irrigate from field SMD checks, the SMD should be matched to the management allowed depletion (MAD) in the central, uniformly irrigated area. Since at the time of this field study, SMD = MAD = 10 cm, it was the correct day for irrigating. Therefore, micro-sprinkler irrigation system improves the existing water productivity; water use efficiency and economic returns through improving DC and SE for the field crops growing under orchard area, increase yield and great control of applied water. Good management of micro-sprinkler irrigation system provides great water and soil conservation and reduces applied water requirement.

Annex 1

Form 1

Orchard Sprinkler Irrigation Evaluation

• 1. Location Nubaria Observer Alaa El-Bably Date 6/17/2015

• 2. Crop citrus, root zone depth 1.5 m, MAD 50%, MAD 10.0 cm

• 3. Soil: texture sandy loam, available moisture 4.1 cm/30 cm, SMD 10 cm

• 4. Tree: pattern square spacing 7.2 m by 7.2 m

• 5. Sprinkler: make BE, model B-21, nozzles #1 by cm spacing 7.2 by 7.2 m, location to trees center

• 6. Irrigation: duration 24 h, frequency 21 days

• 7. Rated sprinkler discharge 0.222 m³ h at 20 psi and diameter 8.0 m

• 8. Sprinkler jet: height 1.0, interference negligible

• 9. Actual sprinkler pressure and discharge (see back for location):

Sprinkler locations	Test	2	3	4
Pressure (psi)	19	21	18	19
Catch volume (l)	4	4	4	4
Catch time (s)	54	52	55	54
Discharge (m3 h)	0.244	0.245	0.244	0.243
Wetted diameter (m)	7.8	8.1	7.8	7.8

1. Comments: sprinkler performance good with smooth rotation

• 10. Container row test data in units of cm, volume/depth ml/cm

  Test: start 7:20 pm, stop 8:00 am, duration 12 h 40 min = 1 2.67 h

Catch (cm)	7.1	6.1	6.4	7.1	7.1	5.31	1.3
Rate (cm h−1)	0.56	0.48	0.51	0.56	0.56	0.41	0.10

• 11. Discharge pressures: max 21 psi, min 18 psi, ave 19 psi

• 12. Comments: The citrus tree branches did not obstruct the sprinkler jets and the sprinklers rotated smoothly and uniformly. The system is the portable hose-pull type.