DAERA Notes: Horticulture

TOP FRUIT: In a year when apple crops in many European countries were significantly reduced by spring frosts and poor growing conditions, local Bramley growers saw better than average fruit set and reasonable growing conditions through late spring and summer months.

While it is always gratifying to see decent yields in many Northern Ireland orchards, a note of caution must be sounded regarding the mineral composition of this fruit and, from that, its suitability for medium to long term storage.

Most Bramley fruit samples analysed this autumn show calcium (Ca) readings of between 3.6mg per litre and 3.9mg per litre, appreciably lower than the recommended minimum of 4.5mg per litre. Similarly, the phosphorus (P) values in fruit averaged below 7.0mg per litre, where the preferred minimum for longer term storage is 9.0mg per litre. The reason for such poor fruit nutrient composition is probably the weather. Low sunlight levels and cool mean temperatures throughout August, followed by a warmer September with rainfall to swell the fruit rapidly, faster than roots could uptake the Ca and P at levels needed. Foliar nutrient sprays will have helped to counteract this problem to some extent, but the indication is still for low storage quality of the crop into 2018.

Monitor stores carefully and sample fruit at regular intervals if you intend to hold stores longer than six months. Keep an eye out for bitter pit (‘tick’) arising from early spring, especially once the suppressing influence of ‘Smartfresh’ treatment begins to wear off. Since low temperature breakdown (LTB) disorder is at higher risk when P values are low, run stores slightly warmer than normal (40 degrees Fahrenheit) and check fruit flesh for any signs of disolouration. As ever, run internal fans frequently through the day to circulate the store atmosphere and monitor gas levels closely.

Protecting horticultural crops against cold weather

This is a timely reminder to protect horticultural crops against cold weather. Don’t let the unseasonably mild weather experienced during October make you complacent about protecting your horticultural crops this winter. Remember the winter of 2010 when Northern Ireland experienced an overall average temperature of -0.6 degrees Centigrade which was the coldest December on record. These extreme sub-zero temperatures caused wide spread damage to commercial horticultural crops and nursery irrigation facilities.

Plants in containers are more likely to suffer winter damage than field grown plants. The root system of container grown plants is above the ground and exposed to much lower temperatures than in the soil. Freezing damage occurs when ice crystals form within plant tissue and rupture the cells. Research has shown that roots can be killed on plants, such as Ilex (Holly), at -4.0 degrees Centigrade. A lot of plants initially appear to have survived the sub-zero temperatures but collapse when growth starts the following spring. Desiccation or drying occurs because water uptake by the roots is exceeded by loss from the leaves and stems. This happens when the root ball is frozen and the air temperature begins to rise. The effect is made worse by cold winds. As we did not experience cold winds in 2010 at the time of the low temperatures, frozen root damage did not show on many plants until growth restarted in spring.

The extent of winter damage can vary depending on the location of a nursery or farm and between regions. Minimise the risk of damage to your horticultural crops and equipment by:

Using appropriate insulation and frost protection measures.

Bringing plants under protected structures and using wind breaks.

Covering plants with protective fleece materials.

Careful watering of plants, to avoid overwatering.

Draining out irrigation systems and equipment before cold weather sets in.

Setting thermostats to give a regime -1.0 degree to +5.0 degrees Centigrade.

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