PJ Phelan: Separating fact from fiction in the push for greater yield

■ Adequate crop nutrition;

■ Avoiding weed competition;

■ Provision of 100pc leaf cover free from disease;

■ Keeping the crop standing.

Adequate crop nutrition

For most of us, crop nutrition is all about soil analysis (phosphorus, potassium and soil pH) and making an assessment of nitrogen requirement from crop type, soil type, crop rotation and rainfall levels over the past few months.

There is very little soil analysis for the essential minor elements, for which applications are determined either by field history and identification in the field, possibly by someone whose main interest is to make a sale.

This year there has been a surge in sales of trace elements driven by drought conditions. We have numerous products containing a little bit of everything and little prospect of doing anything for the crop.

One inch of rain will beat most products, and in the absence of rain there is no long-term benefit.

This week you should get a foliage sample analysed from every field to which trace elements are advised. Sample before application of any further nutrients and again if you wish, in the interest of science 10-14 days later. The result will do little for this year's crop but will give valuable information for the future.

While you have to do soil analysis to comply with the Nitrate Regulations, there is much more valuable information to be got from a field history of foliage analysis. Individual nutrient levels are important for growth but the real determinant of yield is the ratio of nutrients that actually get into the plant.

Recently I have found several crops short of lime, in fields where last year crop growth was satisfactory. The signs of lime deficiency include the oldest leaves being purple, poor tillering/growth and thickened roots.

The solution is to apply granulated lime immediately followed by ground limestone next autumn after harvest.

In recent years, interest in bio- stimulants and seaweed products has increased for crops under stress but this may well fall into the category of recreational farming - filling the need to do something without proof that it will do anything.

Weed control

Weed control is a must for crop growth, ease of harvesting and, for many, visual appearance.

The cost of broadleaf weed control in spring crops should average less than €20/ac, but I have seen programmes this year costing over €25/ac - justifiable on some fields but rarely over the entire farm.

Granted, this year many sales people are unable to view crops due to Covid restrictions and in the event of a farmer not being able to list all weeds present, a more precautionary approach has to be adopted. That is not in accordance with Integrated Pest Management (IPM) and is also a cost that needs to be avoided in a year where grain price prospects are poor.

Disease control

The price of grain and the cost of disease control are the greatest complaints by most tillage farmers.

Reduced rates are the order of the day and some farmers, no matter what rate is recommended, will knock off another 10-20pc.

With the rate of loss of active ingredients, due to legislation, and the speed with which diseases develop resistance, we need to move very carefully - last Wednesday was the last day for Bravo (Chlorothalonil).

The short lifespan of many chemicals, the need for at least two actives in every tank cannot be overemphasised.

Timing for fungicides on spring barley is:

T1: Late tillering

Teagasc trials indicate a yield loss of 0.3t/ha where application is delayed to gs 31-32.

T2: Flag leaf to awns visible

Teagasc trials indicate a yield loss of 0.4t/ha if application is delayed to flowering.

Growth regulators

Growth regulators should not be applied to stressed crops; applied before gs 31 can increase tillering and maintain help to maintain existing tillers.

Later applications will reduce crop height and reduce lodging.