The Carbon Positive tomato crop has now been growing for 13 weeks. Our estimated harvest date is the 5th March, so just under six weeks remaining until harvest. All treatments have had a good fruit set and are reasonably disease free (minus a small amount of bacterial speck). We are on track for a good result at harvest. There are visual differences between the treatments. The conventional treatment has a dense canopy, the regenerative treatment has a more open canopy and the fruit is more exposed. The hybrid is somewhere in between. Management for the month of January has included three spray applications, two irrigations and one granular fertiliser application. More on this below.
Canopy Development Week 2 – 13
Pest Management
In mid-January we started to see holes appearing in tomatoes, caused by corn ear worm/tomato fruit worm. The first insecticide application we used (Benevia) is registered for chewing insects, so caterpillars were targeted early in the season. However, subsequent insecticides have predominantly targeted sucking insects (psyllid/thrips/aphids/whitefly). We applied Uphold (spinetoram) across all treatments to control fruit worm. The crop was inspected five days after application, and found no active caterpillars. Additionally, we still haven’t seen any psyllid on the sticky traps in the field, which is positive!
Nutrient Management
We have been regularly monitoring soil nitrate levels using the Nitrate Quick Test method. Nitrate levels have been declining since side dressing, which indicates that plant demand is exceeding supply of nitrogen. Fruit set has been good and we want to ensure there is enough energy in the canopy to increase fruit size (and yield).
Additionally, we have been doing monthly leaf tests to look at nutrient levels in the tomato leaves. There have been signs of leaf rolling, and purpling along the leaf margins in all treatments in January. This was more distinct in the Regen treatment. This is an indication of low phosphorus or potassium causing plant stress.
Leaf tests showed lower than optimum Nitrogen percentages in the leaf for this stage in the season, as well as low P and K percentages (graph below showing N%). The Operations Advisory Group decided to apply a late application of fertiliser across all treatments. The Regenerative treatment has appeared stressed compared to the other treatments in recent weeks. There has been concern as to whether the canopy is big enough to size the fruit already set. The OAG used the information available to make a justified ‘grower decision’ to address the apparent nutrient deficiencies.
Nitrogen concentrations in the leaf were lower in the Regen treatment than the other two treatments, so we decided to apply a higher rate of N, to support the plants to harvest. The OAG decided to apply YaraRega 9-0-27.5. The Conventional and Hybrid treatment had 9kg N and 27.5kg K applied (100kg/ha). The Regen treatment had 18kg N and 55kg K applied (200kg/ha). This is somewhat counter intuitive for the Regen treatment, however all of the treatments have now received the same amount of N, around 90kgN/ha. Even with this application the Regen plots have had much less potassium applied compared to the other two treatments.
Drone Application
Fertiliser applied late in the season is normally done using a tractor mounted spreader. However, because our plots are 12m wide, we are unable to get the desired spread width this way. We worked with Airborne Solutions to apply the fertiliser with their drone, to be more targeted with our application, plus avoids damaging the plants by driving over with a ground spreader. The spread of the product was uniform and spread to the 12m width of our plots. The drone carries 40kg of product so was a quick job to get done on our 1.5ha.
