Potato Review

32 POTATO REVIEW MARCH/APRIL 2023 N OW is a good time to re ect on the success – or failure – of your irrigation strategies and lessons learned in the tough 2022 growing season. In general, where water was available throughout the season, well thought-out irrigation strategies came into their own, protecting yield and quality. However, growers who ‘teased’ potato crops with water when soil moisture de cits were very high, lost out. Andrew said: “Too little water – or too much – can impact on yield and quality. Fluctuations in water availability to the root zone of the crop can increase incidence of secondary growth and even cause internal necrosis.” Last year, part of the problem for many growers who had planned on irrigating was the dry winter 2021/22, and when river levels dropped in the summer, the Environment Agency banned extractions from rivers. “ e lessons learned from this is that when planning your crops, you need to know the water capacity you will need and have the con dence that you will be able to do the job properly. For example, if you apply 25mm of water, that is equivalent to 250,000l/ha. 250 cubes of water weigh 250 tonnes,” said Andrew. “Once you are clear that you have the capacity, you can decide how you prefer to build your irrigation strategy, choosing between model-based irrigation, which uses predictions of weather and soil moisture, and/ or the use of tensiometers and in-crop sensors. “We need to get better at monitoring and measuring what is going on in the soil and the critical times for irrigation.” Timing of measurement is key, and Andrew suggests digging across the ridge down to 50-60cm and looking at the rooting zone and to assess the soil moisture levels. However, he warns not to leave it until too late as then any application of water would have a limited, if any e ect. Moving on to talk about irrigation tools, he points out that booms, rain-guns and drip systems all have advantages and disadvantages. “Trickle irrigation makes the most e cient use of water, as it can be applied accurately with sensors. It works better than the other methods in hot, dry seasons as you do not lose so much to evaporation.” As water is applied little and often, room can be left for rainfall when it is forecast, he adds. However, costs of set-up are considerable, and it is an ongoing process that needs careful management, and drip irrigation is not suitable for rectifying a problem as not enough water can be applied quickly. Rain-guns aremore of a ‘ re-brigade’ approach which can be useful, says Andrew. However, because of the speed of application, 25ml can atten the haulm, and it can lead to run-o . “If soils are smeared, in ltration is compromised and the water does not reach down to the root zone, the water is lost. “If it is very dry, the ‘ re-engine’ approach can sometimes lead to too much water going on, particularly if it is followed by heavy rain, as too much water can lead to growth cracks. ” ese can occur when the skin is unable to stand the internal pressure created by very wet irrigation regimes which leads to over- hydrated tubers. Water rates can be adjustedwhen using booms, which facilitates a more uniform application of water than when rain-guns are used, however, they can still create run-o if the eld is on a slope. “When choosing your eld for the crop, it is a good idea to think at the same time about your preferred irrigation method, any e ects of topography and whether you have nearby water storage areas, boreholes and rivers. ANDREW GOODINSON Based in Herefordshire, Andrew is an Agronomist and Potato Specialist at Hutchinsons, for whom he has been working for the past 16 years. He looks after nearly 8,000 ha of farmland, ranging from Cirencester, to the Welsh borders, south Shropshire and Worcester. Andrew Goodinson has some tips to help growers decide irrigation strategies and reduce the incidence of diseases such as common scab and powdery scab. Ensure irrigation strategy success IRRIGATION Soil type, irrigation and varietal susceptibility all play key roles in reducing the incidence of common scab (Streptomyces scabiei). The powdery scab pathogen produces circular pustules on the tubers which can act as ‘volcanos’ after they rupture, says Andrew.