Jun 8, 2020

Stay alert to cherries’ water needs

(Sponsored) While the cherry harvest has come and gone already for some growers, the majority will soon find themselves in that water-critical month prior to harvest — and they’ve been urged to keep irrigation at the front of their minds.

This last month before harvest is a crucial stage for the cherry fruit as it bulks out, matures and ripens. But in a bid to conserve water supplies and improve their orchard sustainability many growers now practice regulated deficit irrigation (RDI), increasing the need for water-use efficiency.

“The period between the end of pit hardening and harvest sees rapid cell division in the fruit,” says Mike Williams of OMEX®. “It’s a water-dependent process. It’s also when next season’s flower buds start to develop.
“If your irrigation calculations and RDI approach are leading you towards an irrigation rate of only 55 or 60 per cent ET, then it’s vital that the tree can access and utilize all that water,” he points out.

“The research and evidence for RDI is good, you want to reduce your water use, you know it won’t affect your yield. But that’s a carefully calculated decision; you can’t afford much leeway. The sums have to be accurate so that the tree gets what it needs.”

‘Pre-flight’ checks, to base irrigation decisions on firm evidence, will already have been carried out by most growers. “Soil moisture levels, water composition, soil samples — all those should already be in your log, as the basis for your irrigation calculations.

“So far, so good. Now you need to be sure that the tree is able to access as much as possible of that reduced water volume,” Williams warns.

“If your soil’s water penetration is compromised, the trees can effectively find themselves under-irrigated — the lower rootzone dries out. Meanwhile, near-surface roots remain saturated — which can make them more susceptible to root diseases — and the excessive soil moisture can favor crown and collar rot.”

Physical or chemical in origin, water penetration issues can be addressed relatively simply. While physical causes, for example compaction or a hardpan within the soil profile, require mechanical action — “Difficult to achieve mid-season,” acknowledges Williams, “but it can be added to the ‘to do’ list” — chemical causes can be addressed
in-season.

Excess magnesium or sodium causes individual clay particles to clump together, blocking the soil pores. To displace the magnesium and restore water penetration, calcium can be added to the irrigation water.

“Gypsum is one option, and inexpensive, but for most cherry growers using drip or micro-irrigation systems, it comes with a major disadvantage,” Williams warns. “Even small traces of bicarbonate in your irrigation water will risk blocking your system with lime deposits.”

To avoid this, Williams suggests growers turn to solutions containing calcium nitrate OMEX® has developed its own calcium nitrate formulation — Cell Power® SLYCE® Ca8% — which also contains humic acid.
“Humic acid increases the capacity of the soil’s colloidal structure,” explains Williams. “By creating a more friable soil structure, it increases water-holding capacity and aeration.

“Short-chained sugars are an additional component in SLYCE®. As well as maximizing the soluble calcium, these can help to stabilize aggregates in surface soil and improve water infiltration.”

Although SLYCE® contains calcium, growers shouldn’t regard it as a substitute for foliar applications of calcium used to improve cherry flesh and skin quality, warns Williams.

“To reduce or prevent pitting and cracking, higher rates of calcium applied directly to the fruit are required, as in Cell Power® Calcium Gold. Its formulation — which improves the plant’s ability to absorb calcium — not only allows a lower calcium loading but also much later application dates.”

Learn more at www.omexusa.com.

The product names and brands referenced here are registered and trademarks of OMEX® Agrifluids, Inc.

© OMEX® Agrifluids, Inc. 2020.