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December warm and wet, January HOT
December was a warm, wet month in the greater Auckland region, it did not start to really heat up until the 27th of December. The crops I visited during the early part of December were not showing stress from the weather. It was a slightly different picture when I visited growers on the 29th. The crops were still in good condition but there was enough to indicate some TLC was required. One week into January the full force of the hot weather is keeping me on my toes.
I think growers who applied ReduFuse to their glasshouse roof in late spring will be happy they did so. The ReduFuse will help spread the light better in the crop and keep the lower leaves more active and transpiring, which will help the plant and create more humidity/moisture around the plant, protecting it. It has been quite windy, so don’t be afraid to trap your humidity in your greenhouse by squeezing your wind side vent. It will mean your glasshouse temperature rises, but if you can maintain higher humidity in your greenhouse it should benefit your crop.
Irrigation, water content and EC control is a major factor to successfully keeping a plant healthy, regardless of the age of your plant, this should be your main focus. The water will heat up which means oxygen levels in the water will deplete. It is a major bonus if you are lucky enough to keep your water cool. For irrigation lines (especially black PE lines), that are exposed to the sun, which happens when the plants are small at replanting, I would not hesitate to over-irrigate in the middle of the day until the sun goes over and the lines are shaded just to stop the water becoming to hot. Hot irrigation water on young roots leads to unnecessary root health issues. Hopefully, with older plants, the irrigation lines are not exposed to direct sunlight for long periods and the need for constant replenishment from the plants will help keep the lines cooler. When I would plant a crop in the first week of March, I ordered large 60cm plants to get into production faster but the bigger plant also had the added benefit of shading my PE lines when the sun went past 2pm. I also had white PE lines. Growers seem to have different opinions on the colour and which is best, but for the time of the year I was planting I preferred the white PE lines.
My tip, for planting a young plant, this month is water small amounts often and don’t wait until your entire greenhouse is planted, start your cycles after the first row is planted. If you are able, please do not plant cucumbers after 10am unless you have screens and can shade (I don’t advise using shade screens at any other time for tomato or cucumbers crops unless you are pulling out). If you cannot finish planting by 10am, keep your plants in a shaded area go back at 5pm to finish planting. It is hard if you have a large number of staff but to prevent root death and plant stress this is the best option.
Even though your plant has ample amounts of light to carry a high fruit load, I suggest if you are seeing any stress then don’t hesitate to reduce your fruit load, not drastically and depending on your crop report. As an example, some cucumber growers will be pruning at 2 on 1 off, but I would consider 1 on 1 of, to keep both the plant health and fruit quality up (especially on older crops).
Looking at what the mid to long range weather forecast is predicting, a heat wave is on its way. Our cousins in Australia are having some extreme temperatures and even though we won’t reach their high’s it is generally a good indication some hot weather is on its way here as well. So, buckle in and be prepared as best you can.
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Article Written by Stefan Vogrincic, Consultant, Grower2Grower