Being prepared increases the likelihood of a successful almond harvest.
The number one concern for growers approaching harvest should be controlling navel orangeworm (NOW) in their orchards. Mel Machado, director of grower relations for Blue Diamond Growers said timing of spray applications for this pest is critical to control and minimizing nut damage due to NOW.
Timing hull split sprays should be at the top of every grower’s harvest preparation checklist, Machado said.
“You don’t want to be too late with your hull split sprays, you want to make sure you get good coverage.”
Timing and coverage can be challenges for growers. It helps to understand the life cycle of NOW to plan spray applications for when they will be most effective. Hulls split earlier at the tops of the tree canopy than those on the lower third of the canopy. Growers and farm managers are also advised to complete their spray application in less than five days for the best NOW control. Those who do not have the equipment to accomplish this might want to think about aerial applications, Machado said.
Aerial spray applications in almonds can be a controversial subject, Machado said, but it is important that the hull split spray be effective in knocking down NOW numbers in the orchard. Walnut growers with NOW infestations are using aerial sprays to achieve better coverage, Machado pointed out. Those applications may make sense for some almond growers.
Ants are another insect pest that can wreak havoc with nut yield and quality at harvest. Windrowed nuts left on the orchard floor for several days become a feast for ants. High numbers of pavement ants or southern fire ants can build quickly in the weeks leading to harvest. Ants will head into windrowed nuts and can eat/damage a significant amount of kernels in a short time.
Ants are easy to control with baits, Machado said, but growers need to be aware of ant infestations prior to harvest because it takes time for baits to work.
Strategic Deficit Irrigation
This harvest preparation step has to be done right, or there can be a negative impact on crop yield. Spencer Cooper, Senior Manager, Field Outreach and Education for Almond Board of California, said strategic deficit irrigation prior to harvest is a great strategy to reduce incidences of hull rot as well make for a cleaner harvest, but care must be taken to correctly measure tree stress during that time, Cooper said.
Research done by David Doll, former University of California farm advisor in Merced County, showed that some water stress leading up to harvest is acceptable. Water reductions should start in the 10-20 percent range and Cooper advised use of a pressure chamber to monitor the trees stress. By inducing a mild stress (-15 bars) at the onset of hull split it has been shown to increase the uniformity of hull split as well potentially reduce the severity of hull rot incidents. The deficit should be maintained for two weeks. Full irrigation must resume to avoid loss of kernel weights.
Cooper stressed that before a grower implements Strategic Deficit Irritation (SDI) to confirm that there irrigation system has the capability to meet peak evapotranspiration (ET) demand, if the system can not do this than the grower may already be operating at a deficit for the season so there would be no need to implement a deficit. Maintaining stress too long or starting it too early may have a negative impact on kernel weights. Doll’s research showed that understanding the developmental state of the tree in relationship to when it completed kernel fill, timing of blank split and hull split and timing of harvest will determine how much and when deficit irrigation should be done.
Good yield estimates are essential to a nutrient management strategy in almonds.
Gabriele Ludwig, Director of Sustainability & Environmental Affairs for the Almond Board of California, said fertilization rates should be based on realistic, orchard specific yield, and all nitrogen inputs should be accounted for. Adjustments can be made for spring nutrient and yield estimates.
A pre season fertilizer plan should be based on expected yield minus the nitrogen (N) in irrigation water and other inputs. Following full leaf out, conduct a leaf analysis. In May, a review of the leaf analysis results and an updated yield estimate can lead to adjustment of the fertilizer plan. For every 1,000 pounds of kernels harvested, 68 pounds of nitrogen, 8 pounds of phosphorus and 80 pounds of potassium are removed.
Research shows that applications of N to match tree demand in as many split applications as feasible is improves efficiency. Recommendations are for 20 percent N in March, 20 percent in April and 30 percent in May. The remaining N should be applied post harvest.
Using the same nutrient management plan every year for every orchard reduces nitrogen use efficiency.
Orchard Floor Preparation
Clean, smooth orchard floors will go a long way in keeping dust generated by harvest equipment under control and sending a cleaner product to the huller. Preparing a smooth, level orchard floor will also eliminate low places or holes where nuts can gather and be missed by the sweeper. This also reduces the need for extra passes down the row.
Attention to problem areas on floors should have been done after last year’s harvest, Machado said, and it is too late to make major changes prior to this harvest.
Cover crops and/or weeds should be mowed. Rows should be scouted for excess dirt, rocks and trash. Removal will help deliver a cleaner product to the huller. Machado said dirt, rocks and trash picked up picked up in the windrows slows the hulling process, raises costs to the grower and may impact nut quality.
If floors are prepared and sweepers are adjusted properly, there will be less dust generated, Machado said. Keeping dust levels down with some soil types will always be a challenge, but a smooth floor will go a long way in keeping soil out of the windrows.
More challenging soils may require use of dust inhibitors, watering or shells from last year’s harvest to reduce dust on roads and yards.
Think ahead to avoid wrecks, Machado said. Much of the preparation for almond harvest began at the orchard design stage, but if changes have occurred since planting, some planning is in order.
Orchard access and egress need to be evaluated to avoid traffic jams. Routes for sweepers and harvesters should be planned ahead of time to avoid making extra passes.
Machado said that adjusting harvest equipment to match orchard conditions and training operators to reduce speed could help reduce dust.