To get the best return growing processing tomato homogeneity is king. The crop needs to be maintained to give even size and growth. Here in the first of two articles we discuss the roles of nitrogen and calcium in achieving this.
Feeding crops is important but nitrogen can make plants grow too vegetative, leading to poor and inconsistent establishment. If processing tomatoes do not evenly establish that follows through to harvest with inconsistent size and levels of maturity.
The majority of nitrogen applied to crops gets taken up in the nitrate form (regardless of what form it is applied as) due to instability in the environment. Nitrate nitrogen is processed in the leaf and leads to production of the growth hormone auxin. High auxin levels in plants make them apical dominant, meaning that as crops receive more N (nitrate) they become progressively more vegetative.
Unlike nitrates, the amine form of nitrogen is processed in roots and leads to the production of a different growth hormone – cytokinin. Amine nitrogen encourages more investment in reproductive growth and rooting. This is a more desirable type of growth for processing tomato crops as it gives good roots, more even establishment, and better and more even fruit production.
Unfortunately due to the rapid conversion on amine to nitrate in soils this better growth habit is hard to achieve in practice.
Levity have developed LimiN, a technology that combines amine N with other nutrients and holds amine N in the form it is applied – giving more fruit development and less vegetative growth.
Here we present two graphs from experiments on determinate tomato plants. The first graph shows how conventional nitrogen sources (urea, calcium nitrate and ammonium nitrate) generate rapid shoot growth, whereas the same amount of nitrogen supplied using Lono (Levity’s LimiN technology) gave slower shoot growth.
The second graph shows the impact of this on fruit number. Lono (Levity’s stabilised amine formula) produced highly significant increases in fruit compared to conventional nitrogen sources. Supplying stabilised amine nitrogen encourages the crop to invest in fruit rather than vegetative growth.
If a plant is growing in one place it is not growing in another, by taking care of nitrogen inputs we can focus growth in the right place to gain yield.
To get even flower set and to reduce blossom end rot it is important to get good calcium levels in the fruit, but throwing large volumes of calcium at the crop is an ineffective way to achieve this.
Calcium absorption in plant cells is linked to ‘polar auxin transport’ therefore parts of plants high in auxin absorb calcium easily (if available) and parts of plants low in auxin absorb calcium sparingly (no matter mow much is supplied).
In common with most crops, tomatoes struggle to get good calcium levels in the fruit. This is due to the fruit being a low auxin tissue and therefore a poor sink for calcium. When the fruit is young and small (<2mm) it is in the cell division stage where the new cells that will become the fruit are being created and at this point auxin levels are good, however as the fruit starts to increase in size cell division is no longer occurring the cells are instead expanding and auxin levels are lower. This means as fruit increase in size the ability to absorb calcium decreases.
To get even flower set (vital for getting the crop even at harvest), and to reduce blossom end rot it is important to apply calcium between flowering and 2-3 mm fruit size. This is when new cells that form the fruit are formed and applications are more effective in this window.
For best results crops will benefit from use of products containing LoCal technology such as Levity’s Albina. LoCal improves calcium absorption in low auxin parts of plants and can be used to get calcium into fruit where the natural ability to absorb is low.
To give good root growth and better growth habit apply Lono at 5 litres per hectare, commencing at transplanting and making regular applications at 3-4 week intervals. This will keep roots actively growing, encourage a good growth habit, and ensure the plant focuses on fruit production.
To improve fruit calcium levels and give even fruit set use Albina at 1 litre per hectare at flowering. Repeat with one more application after two weeks. This will be more effective than more frequent applications of standard formulations.