IRRIGATION SCHEDULING AND TECHNIQUES IN GRAPES

1. IRRIGATION SCHEDULING AND TECHNIQUES IN GRAPES Next End

2. INTRODUCTION Irrigation • Water supply should be ensured in vineyards during period of active growth and berry development stages. Irrigation should be given to field capacity. • During establishment period of vines after planting, frequent irrigation during dry months may be required. Watering immediately after pruning and fertilizer application should be done without fail. Previous Next End

3. Irrigation at an interval of 5-7 days during initial berry development stage till they become pea size and at 10 days interval till maturity is better for good yields. Watering should be withheld from 25-30 days prior to harvesting to ensure quality of produce. Quality of irrigation water is also important. Excess salt content in irrigation water, with EC value of more than one causes injury to vines. Previous Next End

4. Phosphoric acid and dry potassic fertilizer such as sulphate of potash can be used as sources of P20S and K20 for application through irrigation systems. • Numerous formulations containing two or more nutrients are available for fertigation. About 30% saving in quantity of fertilizers can be achieved through this technique. • Irrigate vines immediatelyafter planting. Vine water use is very low in the first 6 to 8 weeks, but the vines have a small root system that should be kept moist. • Initially vine growth (including root growth) is supported by stored carbohydrates in the cutting/rootling. Establishment phase Previous Next End

5. FERTIGATION • Application of fertilizers through irrigation system, fertigation, has been tried in grapes also. Drip irrigation system is ideal for fertigation and only soluble salts are applied through irrigation system to prevent clogging of emitters. Urea is widely used for fertigation since it readily dissolves in water. Improved yields by applying 300 kg urea/ha for 60 days after October pruning at 5 kg/ha/ day. Previous Next End

6. The soil should be kept moist to promote further root growth. If the soil becomes too wet, root growth will be inhibited. In most soil types this means applying small amounts of water daily for the first few weeks then less often. • To ensure the moisture of the soil is at an optimum install soil moisture monitoring devices (e.g. tensiometers). Maintain the soil moisture tension in the vines root zone between 10 and 60 centibars. Previous Next End

7. YOUNG VINES • The aim is to maximise vine growth in years 1 to 3. Maintaining moist soil throughout the growing season will help to achieve this. • Soil moisture can be maintained by adjusting irrigation according to soil moisture readings (e.g. tensiometers or gypsum blocks). • Soil moisture should be maintained between 10 and 60 centibars. Previous Next End

8. ESTABLISHED VINES • Maintaining soils in the readily available moisture range will maximise yield throughout the growth cycle of the vines. • Irrigation techniques such as RDI and PRD can also be used to manage vine growth and to manipulate fruit quality and yield. • Grape is a shallow feeder. Light and frequent watering is better for grapes. • Water requirement of grape are very high during berry growth. • This period coinciding with hot and dry weather, more water is required at this stage. • Least water is required during fruit-bud formation. This period if coincides with cloudy weather and rains, watering are totally to be stopped. Previous Next End

9. Reduced irrigation during ripening, i.e. (one month prior to harvesting) improve the quality of grapes and hastens ripening. Too much stress during ripening can also increase the berry drop at and after harvesting. • Currently due to the shortage of water, grapes are irrigated through drips. • The number of drippers/vine and their placement are very crucial in drip irrigation. The active feeder root zone is to be wetted by the water discharged through the emitters. Previous Next End

10. Since the wetted pattern is more horizontal than vertical in clay soils but more vertical than horizontal in sandy soils, more emitters with low discharge rate for longer duration are advisable to get good results with drip irrigation in sandy soils. • Inadequate wetting of root zone reduces shoot vigour and weakens the vines. Gradually they develop deadwood and go barren 7-8 years after planting. • The quantity of water to let through drip irrigation daily depends not only on the stage of growth of the vine but also the evapo-transpiration in a vineyard. • Putting these two factors together the water requirement of grapes through drips is given in Table3. Previous Next End

11. Water requirement of grape through drip irrigation Previous Next End

12. Grape is sensitive to chlorides and total salts content in irrigation water. • Water with electrical conductivity of less than 1mmhos/cm, chlorides less than 4m.e/litre, sodium adsorption ratio less than 8.0, residual sodium carbonate less than 1.25 m.e/litre and boron less than 1.0 mg/kg is considered safe for irrigation grapes. • Raising a bund of loose soil to a height of 1’ along the vine rows and mulching the soil around the drip zone by sugarcane trash or paddy straw can conserve the soil moisture and save irrigation water. Previous Next End

13. Advantages of drip irrigation system • Water saving to the extent of 60 % as compared to traditional surface irrigation method • High water application efficiency • Increase in the yield to the extent of 25 - 30 % over traditional irrigation methods. • Use of water soluble fertilizer, very high FUE with fertilizer saving to the extent of 25 to 30% Use of saline water is possible • Reducing inter-culturing and weeding cost Previous Next End

14. Excellent soil health and maximum soil microbiological activities Saving in labour cost, due to atomization • Excellent and cost effective for horticultural crops - widely spaced, low cost and long duration crop. • Adoptable for undulating topography, variable soil types and all crops • Adoptable for undulating topography, variable soil types and all crops. Previous Next End

15. However drip irrigation system has also limitations as below: • High initial cost due to solid system • Skilled man-power is required for design, operation and maintenance • Availability of electricity as system is to operate daily or alternate day deposits • The problem of clogging of emitters due to physical impurities, chemical and biological residues of bacteria and algae • Periodical maintenance such as cleaning of filters, flushing of piping network and pressure regulation in the system Next End Previous

16. 6. Treatment of back water flush system, (Sand filter cleaning), acidification (Chemical clogging) and chlorination removal of algae and bacteria are tedious and time consuming . 7. Breaking of lateral pipes due to cultural operation, rats and other animal troubles • In spite of the above limitations and some problems the micro-irrigation system has proved to be the best system amongst all irrigation methods. Previous