In The Orchard The variable weather conditions are continuing throughout most of the almond growing areas, with the unseasonal rainfall events providing the most difficulty this season. by Brett Rosenzweig
With all growers switching their attention to harvest, the following checklist will provide some helpful reminders and assistance over the coming months: • Keep up to date with weather forecasts. Last edition I mentioned to keep an eye on the weather forecasts for impending heatwaves and to adjust irrigation schedules accordingly; particularly, as orchards are commonly drier through harvest. The same still applies, but during harvest, consideration must also be given to rainfall events, regardless of their predicted amount. Even small rainfall events at this time of the season are contributing to difficulties such as morning dews and shortened harvesting hours. The weather site links are: http://reg.bom.gov.au/products/reg/access/ http://www.australianweathernews.com/forecast_OCF.htm http://www.bom.gov.au/watl/ • Check storage pads and bunkers. The heavy rainfall events and localised flooding during summer should prompt a rethink on location of storage pads and bunkers and whether they are effectively protected from sudden downpours and flooding. Did your storage pad or bunker have free-standing water after the recent rainfall events? Did runoff water move from another part of the property through the pad or bunker? Do you have adequate tarps etc to cover the stockpiles if we have a continued wet harvest? Stockpiles are best located in a north – south orientation with no troughs for water to accumulate in. Moisture content of the fruit must be measured before shaking, or before pick-up and stockpiling following rain interruptions. Research has indicated the incidence of mould growth and food safety risks increase dramatically when fruit is stored with kernel moisture of greater than 6%. Refer to Fact Sheet 10. • Soil Salinity and pH. Even though rainfall has been above average so far this season, it will still be advantageous to take soil samples for salinity and pH analysis. Samples should be taken from approximately 30, 60 and 90 cm or at closer intervals if your soil depth is shallower than 1m. The season’s rainfall would have had some positive leaching effects, so specifically target known salinity hotspots from previous years or known drainage areas where water tables may have risen and consequently brought salt into or close to the rootzone. The same principle applies for drip irrigated orchards, however sample at 20cm from the dripper (within the wetted area of the dripper) and 60cm from the dripper (the edge of the wetted area of the dripper). High salinity levels 60cm from the dripper could lead to uptake of salt by the tree after light rainfall events as the salt is pushed back into the rootzone. pH should also be tested in addition to salinity, particularly in drip irrigated orchards and those orchards with high fertiliser inputs. Refer to Fact Sheet 09. http://wxmaps.org/pix/aus.vv.html http://wxmaps.org/pix/prec7.html http://www.eldersweather.com.au/ http://www.weatherzone.com.au/sa/murray/renmark
• Post Harvest Nutrition. The ideal weather conditions in spring and summer have contributed to good extension and spur growth, bud numbers, and potentially high flower numbers and small kernel size for next season. This is of particular relevance to Nonpareil, where this has been exacerbated by a generally lighter crop this season. It is therefore important to maintain good tree and bud health, during and after harvest. Many orchards reduced their spring fertiliser applications as a result of the lighter crops and mild weather conditions, and particular attention will now need to be given to timely applications of post harvest fertiliser. Harvest is later than last season, so it may be necessary to start post harvest fertiliser applications earlier to ensure adequate uptake. Applications following harvest should ensure there is still enough potential for fertiliser uptake. • It is important to take into account the amount of foliage remaining on the tree after harvest. If there isn’t enough foliage remaining on the tree (due to the lateness of the season, rust etc), care should be taken to avoid unnecessary “reshooting” of trees if the application rates of fertilizer are too high. Applications of fertilizer when trees have very little uptake or are nearly dormant, can result in the fertilizer sitting in the soil, not readily being taken up by the tree and prone to leaching beyond the rootzone during winter. If the soil temperature is below 18 o C, it would be more worthwhile applying ammonium nitrate, rather than Urea or UAN as Urea doesn’t readily or quickly break down when soil temperatures are below 18 o C. • It may also be worth considering the application of “bud building” sprays using Lo-Bi Urea and other micro nutrients (e.g. Boron and Zinc). Rates for “Bud building” sprays of Lo-Bi Urea are usually 1% or 10kg/1000L. Refer to Fact Sheet 02. • Disease pressure. This season has seen conditions suitable for the development of rust, especially late in summer, when control options have been limited due to withholding periods before harvest. It is crucial to have good defoliation this winter to stop the carryover of the rust spores into next season. Remember, the primary cause for rust carrying over to next season is the rust spores overwintering on any leaves remaining on the tree. Even if the tree is mostly defoliated from rust, weather conditions etc, it is still critical to apply a defoliation spray to remove ALL the leaves. Most commonly used is a 7% Urea defoliation spray but Zinc Sulphate can also be used. • If you don’t already, it may be worthwhile applying a dormant copper spray following defoliation. With higher than normal disease pressures experienced this season, a copper spray during dormancy may help fungal disease management for the following season.
For further information contact: Brett Rosenzweig Industry Development Officer Almond Board of Australia P 08 8582 2055 or 0429 837 137 E: firstname.lastname@example.org