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.

Nitrogen

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.

Calcium

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.