As the long, hot summer continues to cause havoc with crop growing, stopping potato crops earlier than usual offers growers the best chance of a decent harvest, according to the latest advice from Hutchinsons.

Darryl Shailes

Root crop technical manager, Darryl Shailes, says that even the best of irrigation systems or the crops grown in the perfect silt that were planted in great conditions are struggling under the prolonged hot and dry weather the country is currently experiencing.

By early August, most irrigation reservoirs are getting very low and restrictions are being put on some other licenses, he adds.

“During the heat wave in July many crops ceased bulking and only put on dry matter, and were just about kept alive. This rapid increase in dry matter means that many crops especially those that are unirrigated or short of water are already in excess of 24% DM and will be highly prone to bruising.”

Strategic decision making

Darryl believes the best decision for many growers will be to stop the crop even though the yield is low. “To leave the haulm alive under the current conditions will only increase dry matter and yield is unlikely to be significantly improved.

“For some crops even if rain were forecast, their ability to increase yield and tuber size significantly will already be compromised with very poor haulm and will probably cause issues with secondary growth.”

A targeted approach

He says growers may have to target lifting and irrigation where still available to those crops that are most sensitive to bruising. “Where water is available, irrigation pre-harvest even though having no real effect on dry matter, can help to keep more soil on the web and cushion the potatoes to reduce bruising.

“Single handling and correct settings of harvesters and elevators will be even more important than normal to reduce the exposure to bruising as much as possible. A relatively small unbruised crop should be easier to market than a slightly larger but heavily bruised crop.”

Irrigated potential

But it’s not all doom and gloom, says Darryl. “Some well irrigated crops are still bulking and have good haulm and in an ideal world soil moisture deficit should be maintained at around 30mm until flailing and or burn down to reduce the risk of bruising.”

“Normally blight control would need to be continued until all the haulm is dead but with this season with hardly any reports of blight some growers may decide not to treat during the haulm destruction process especially on crop not intended for storage.”