Rainfall . The efficiency of the most common irrigation systems is listed in Table 6. When trees go into water stress, fruit tends to be smaller, too. Underwatered trees lead to low yields. 0000006208 00000 n Spacing of sprinklers/drippers: This is the distance (in meters) between the sprinklers or drippers in the irrigation line. This led to the belief that orchards are better protected against heat waves and a micro-climate is created that benefits the orchard. water released from the micro-sprayer or drip emitter that does not reach the soil, is discussed later since it forms part of the application efficiency of an irrigation system. 0000007900 00000 n 0000001067 00000 n Steps for irrigation schedule plan-ning, using weather data as well as orchard and soil characteristics (adapted from Myburgh, 1993). Different technologies are available to measure or estimate the soil water content, but are not discussed in this article. Zt�h�~F�&����@����V 8. 0000019218 00000 n Growers in SA are world leaders when it comes to the use of low delivery rate drippers, and implementing the concept of a “centralised control continuous irrigation system”. Total tree water use or ET (evaporation and transpiration) is the term used to describe water use by the trees. Irrigation for Cold Protection; Publications. The impact of canopy cover is evident – from there the suggestion that trees should be heavily pruned under conditions of restricted water availability. One of the simplest ways to determine soil water content, or calibrate readings from any apparatus, is still by means of in-situ soil investigations, i.e. A prerequisite for successful drip irrigation, however, is a well-established deep root system that can only be obtained with proper soil preparation. Transpiration (T) refers to the water that moves through the tree/plant and is lost to the atmosphere by evaporation from the surface of the leaves and other aerial parts of the plant. It is expressed as millimetre per meter soil (mm/m) and can be determined in a soil laboratory where the difference between field capacity water content and wilting water content is measured by applying a specific amount of pressure to wet soil. From an irrigator’s perspective, the use of long-term weather data (to develop a basic irrigation schedule), combined with measurements of soil water content (to ensure that they do not tend to over- or under-irrigate over time), facilitates the accuracy of when and how much water to apply. 0000009742 00000 n Automatic weather stations provide accurate information with regard to radiation, relative humidity, temperature and wind speed. H+ �.XD�]7�Mv3ldeaZ�0h� ^���t�i>�v [�� �af&��@�#0X��������E%������M;İ�� �1� endstream endobj 65 0 obj 221 endobj 32 0 obj << /Type /Page /Parent 29 0 R /Resources 33 0 R /Contents [ 42 0 R 44 0 R 46 0 R 50 0 R 52 0 R 54 0 R 58 0 R 60 0 R ] /MediaBox [ 0 0 612 792 ] /CropBox [ 0 0 612 792 ] /Rotate 0 >> endobj 33 0 obj << /ProcSet [ /PDF /Text /ImageC ] /Font << /F2 37 0 R /F3 38 0 R /F4 34 0 R /F5 39 0 R /F6 47 0 R /F7 55 0 R >> /XObject << /Im1 62 0 R /Im2 63 0 R >> /ExtGState << /GS1 61 0 R >> /ColorSpace << /Cs5 40 0 R >> >> endobj 34 0 obj << /Type /Font /Subtype /Type1 /FirstChar 32 /LastChar 247 /Widths [ 278 271 354 584 542 680 625 188 323 323 417 584 219 323 219 281 500 500 500 500 500 500 500 500 500 500 219 219 584 584 584 333 1010 667 563 708 750 500 469 740 729 250 250 656 490 781 781 823 510 823 604 458 604 708 604 1042 708 604 646 333 281 333 469 500 333 427 500 438 510 479 250 427 500 219 219 479 219 771 500 552 500 500 396 385 333 500 438 719 500 438 417 333 260 333 584 354 354 354 0 0 0 0 0 0 0 0 0 0 0 354 354 354 354 0 219 0 0 354 0 0 0 0 0 0 0 354 354 0 278 0 438 531 0 0 0 0 0 740 0 0 0 323 0 0 0 584 0 0 0 552 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 584 ] /Encoding /WinAnsiEncoding /BaseFont /GillSans /FontDescriptor 36 0 R >> endobj 35 0 obj << /Type /FontDescriptor /Ascent 682 /CapHeight 682 /Descent -230 /Flags 262176 /FontBBox [ -177 -250 1167 929 ] /FontName /GillSans-Bold /ItalicAngle 0 /StemV 145 /XHeight 461 >> endobj 36 0 obj << /Type /FontDescriptor /Ascent 682 /CapHeight 682 /Descent -230 /Flags 32 /FontBBox [ -162 -250 1041 911 ] /FontName /GillSans /ItalicAngle 0 /StemV 89 /XHeight 449 >> endobj 37 0 obj << /Type /Font /Subtype /Type1 /Encoding /WinAnsiEncoding /BaseFont /Times-Roman >> endobj 38 0 obj << /Type /Font /Subtype /Type1 /Encoding /WinAnsiEncoding /BaseFont /Times-Bold >> endobj 39 0 obj << /Type /Font /Subtype /Type1 /FirstChar 32 /LastChar 181 /Widths [ 278 271 479 584 542 719 750 240 385 385 469 584 271 333 271 281 552 552 552 552 552 552 552 552 552 552 271 271 584 584 584 375 979 781 698 771 802 635 604 813 833 333 333 719 615 885 844 875 656 875 677 604 719 823 719 1167 813 708 698 438 281 438 584 500 333 531 583 500 583 552 302 542 583 271 271 552 271 958 583 594 583 583 448 427 406 583 510 781 552 510 521 385 281 385 584 354 354 354 0 0 0 0 0 0 0 0 0 0 0 354 354 354 354 0 0 0 0 354 0 0 0 0 0 0 0 354 354 0 278 0 500 521 0 0 0 0 0 740 0 0 0 333 0 0 0 584 0 0 0 615 ] /Encoding /WinAnsiEncoding /BaseFont /GillSans-Bold /FontDescriptor 35 0 R >> endobj 40 0 obj [ /CalRGB << /WhitePoint [ 0.9505 1 1.089 ] /Gamma [ 2.22221 2.22221 2.22221 ] /Matrix [ 0.4124 0.2126 0.0193 0.3576 0.71519 0.1192 0.1805 0.0722 0.9505 ] >> ] endobj 41 0 obj 895 endobj 42 0 obj << /Filter /FlateDecode /Length 41 0 R >> stream To secure high yields of good quality fruit, producers sometimes think it is necessary to adjust their irrigation practices in accordance with the availability of … Notes on the 10th International Fruit Fly Symposium – Reportback on a meeting of Fruit Fly Scientists in Mexico in April 2018, Postharvest treatments aid control of Citrus Black Spot (CBS), Extension Briefs for December 2018 and January 2019, Citrus Black Spot Disease (CBS) Management. If the water applied is not a limiting factor, the type of irrigation system does not influence the transpiration rate of crops. Email: [email protected], ADVERTISEMENTS During periods of severe water shortages, controlled stress can be applied from May onwards with little effect on yield and fruit quality. • How long the cycle must be to apply the correct amount of water; and 2. Irrigators should then be fine-tuning the proposed irrigation schedule by doing on-farm monitoring of the soil water content with a soil auger or physical profile inspections. A newly planted citrus tree should be watered at least weekly with enough water to saturate the soil around the drip zone. 0000002943 00000 n Irrigation strategies must be documented and practiced to allow growers to maintain or increase crop production without depleting our water resources. Allowable depletion: This is the maximum amount of readily PAW allowed to be depleted from the soil profile by tree water use (expressed as a percentage of the readily PAW in Table 1) before the next irrigation. Another factor that contributed to the popularity of drip irrigation is the concept of fertigation, or rather precision farming, where concepts of open hydroponics are utilised to promote more efficient utilisation of water and fertilisers. Soil texture – ensure that the correct soil texture class is used for estimating the soil water holding capacity. The correct amount of water required for irrigation may, however, differ from these calculated values, due to inaccurate estimations of soil water holding capacities and/or diversions in the current weather conditions from the long-term weather patterns. Crop coefficient (Kc): There is a direct relation-ship between ETo for a specified period and the amount of water an orchard needs during the same period. Width of the wetted area: In the case of micro-irrigation, the wetted zone is clearly identifiable on the soil surface and therefore easily measured. Tel: +27 (0)21 870 2900 | Fax: +27 (0)21 870 2915 0000008707 00000 n These trees usually recover faster than water-stressed trees without any canopy reduction. Filda Booysen (Enquiries, Subscribers) A mature citrus tree may need irrigation on intervals of once every two weeks or one month but the entire area under the canopy of the tree, up to within a foot of the trunk needs to get the equivalent of two or three inches of rain per irrigation. With proper irrigation scheduling, yield will not be limited by water st… Water holding capacity: This is the amount of plant available water (PAW) that a given soil can hold within the plant’s root zone, e.g. In general citrus trees have some ability to withstand water shortages and their thick leaves (especially older leaves), low number of stomata on leaves, and waxy fruit help conserve water. 4. 0000005234 00000 n 0000006229 00000 n that actually replaces the volume of water depleted from the root zone. feeling the soil water content with one’s hand.