Brett Rosenzweig - Industry Development Officer In The Orchard
• Boron. Boron is essential for pollen tube growth and fertilisation of flowers. Usually Boron in the tree is deficient and needs supplementary applications. Boron mostly ends up in the hulls at harvest time and that’s why sampling hulls for nutrient analysis is a good indicator of Boron levels. The best form of applying Boron is post-harvest applications, e.g. Solubor rather than spring applications where the Boron can be tied up in the growing fruit. Soil applications of Boron are common practice in California and you can read more in the Almond Doctor blog titled “Post-harvest Boron Applications Can Increase Almond Yields” dated 6/10/09. Are you planning new orchard developments or redeveloping old orchards? In this issue of In The Orchard… I thought I might raise some discussion topics that should be considered prior to planting an orchard. Orchard development only occurs once every 20 to 30 years, hence it’s vital that the appropriate steps are taken prior to planting to ensure a healthy, productive orchard. • Soil Remediation. This step in planting an orchard cannot be over emphasised enough. There are various actions that can be taken in soil remediation including ripping, adding organic matter, altering soil pH or nutrient imbalances and correcting salinity issues. The main aim of soil remediation is to create a soil environment that is free of compaction, an adequate nutrient balance (e.g. Ca/Mg ratio) and has low salinity. Ideally a soil high in organic matter is also preferred but Australian soils are generally very low in organic matter. The cheapest form of organic matter is the one you grow yourself. This could include annual cover cropping (clovers/medics/ryegrass for sprinkler orchards and cereals for drip orchards) or possibly even the mulching of old almond trees. Whilst it’s easier to push an orchard into a burn heap for disposal, there might be better uses for the plant material that goes up in smoke. Refer to Fact Sheet – Supersoils. • Efficient Irrigation. If you had problems with your old irrigation system, a redevelopment phase gives the opportunity to remedy previous issues. Low lying or areas with poor drainage could be sectioned off as a separate valve unit. These areas could be irrigated the same as the rest of the shift unit but in times of excess rainfall or flooding, could be turned off to allow the area to dry out. It’s also worthwhile considering the installation of an A-B system where the pollinators are irrigated separately to Nonpareil. This allows precise irrigation management at harvest and the ability to fertigate according to drop load. Another option to consider is the implementation of a dual sprinkler/drip irrigation system. Sure enough there is a higher cost associated with a dual system due to twice the infrastructure but there could be long term benefits. A drip system enables efficient irrigating and fertigating while a sprinkler system allows for frost control and the establishment of inter-row cover crops to aid in soil stabilisation prior to harvest and an increase in overall soil health. If you do choose to go down this path then consider getting the sprinkler system designed with a lower application rate. My suggestion is to aim for double the application rate of the drip system but still ensuring the Distribution Uniformity (sprinkler coverage) is above 90%. This way sub-main pipe sizes
Harvest will be well under way in all growing regions and by the time this article gets to press most people should be finished Nonpareil and moving onto the pollinators. Here’s a few regular discussion points to consider post-harvest: • Fruit Sampling. In addition to leaf sampling (which should have already been completed!) there is also the option of sampling fruit at harvest to determine a) Hull Boron and b) crop nutrient removal. Hull Boron is a better indicator of the Boron status in the tree compared to leaf Boron. Sample 100 fruit from the same trees you use for leaf sampling and crack out the fruit into its three components i.e. hull, shell and kernel. Ask your lab for a nutritional analysis on all three separate items including wet and dry weights (you need this for the crop nutrient removal). Refer to Fact Sheet – Crop Nutrition: It’s not just NPK. • Check Fruit Moisture Content. With the rainfall that each region experienced mid last month and the significant cooling in temperature in recent weeks, it’s vital the fruit is at the correct moisture content before stockpiling. The correct storage moisture is even more important when the mornings are cool, dewy and the mid row moisture levels have been replenished with recent rainfall. 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%. Remember – Food safety starts in the orchard! Refer to Fact Sheet – What Threatens The Safety Of Almonds. • Soil Salinity and pH . Soil samples for salinity and pH should be taken after harvest. Samples should be taken at least three depths within the wetted area of the rootzone for sprinklers and both 20cm and 60cm from the dripper of drip irrigated orchards. Target known salinity hotspots from previous years or known drainage areas to start with. Don’t forget to test for pH and surface soil acidification in drip irrigated orchards. Refer to Fact Sheet – Soil Acidification. • Post Harvest Nutrition. To get the most efficient fertiliser uptake after harvest, the best time for application is in March or after Nonpareil has been harvested, but remember to ensure the rootzone has sufficient moisture to facilitate uptake. Applications later than this or on dry soil can result in the fertiliser remaining in the soil, not readily being taken up by the tree and prone to leaching beyond the active rootzone during winter. High concentrations of fertiliser in dry root zones can also act as a ‘salt’ causing tree damage. Post-harvest is also the time for foliar applications of Lo-Bi urea, Solubor and other micro nutrients. • Disease and Pests. There are signs of mite damage in orchards again this year. The best form of mite control is an oil spray (winter or summer) during dormancy to aid control for next season. Remember higher water rates and slower ground speeds are needed for good coverage when applying oil. Ground speed is more important than the water rate, 3km/h is a good speed to start with. If your orchard is affected by mites, this is another reason for applying post harvest fertiliser sooner rather than later as leaf functionality and therefore water/ fertiliser uptake is reduced.