Plant growth regulator

Ethrel or Ethephon is a very useful tool for stiffening and shortening the straw – thus reducing the leveraging effect in a heavy, damp crop which leads to lodging.

Assessing when to use it however is crucial; in the absence of lodging a growth regulator will invariably cause a slight reduction in yield. In a strong crop however, it allows you to push the nitrogen slightly further to the point at which the crop would otherwise fall over. In other words, used correctly growth regulators can help you increase yields.

plant growth regulators

The simple Growth Regulator and Lodging Test! Hold the stem base horizontal and see how much it bends; the plant on the left had ethephon at stem extension, the plant on the right had nothing. If it bends over 45 degrees at milky ripe stage, you probably should have growth regulated it or eased off on the nitrogen.

NIAB TAG trials in the UK (where barley is almost always grown with one growth regulator application and often two), invariably shows that no matter what growth regulator is used, if the crop is not going to lodge then there might be a yield reduction in the order of a few percent.

In trials where lodging did occur however, 20-30% yield benefits are often recorded! And remember that these are the high yielding, more valuable crops too where there is more at stake.

As we move to higher yield potential varieties like Planet, particular on farms practicing rotation where the yield potential is greater, ethephon is a very useful tool to have.

Our trials this year are also highlighting the need to get nitrogen into the plant EARLY on many soils; topdressing at the two leaf stage and again at GS30 to ensure that adequate tiller numbers are produced. This can increase lodging but having the option of a growth regulator allows farmers to do this safely.

The spring-off benefit of this is that applying some of the N earlier reduces the risk of high Grain Nitrogen, or a dry period from prevent topdressing at all.

The above does not constitute a recommendation; remember to always consult an agronomist for appropriate advice.

Fall Armyworm products ON TEST

Fall Armyworm pressure has generally been low this year but the pest still remains active, with memories of 2017 still clear in farmer’s minds. Which product to use remains a central question to controlling the larvae effectively and minimising yield loss.

maize fall army worm

Our large scale field trials in Nakuru are examining just this issue, using fully replicated plots to look at the percentage control of the larvae, and then residual activity against re-infestation.

The products included in the trial have been selected for their known activity in the field against Fall Armyworm in the past two years of our trials, so time and resources are not wasted examining products that have not been shown to be effective.

So far the most effective choices are once again; emamectin-benzoate, acephate, indoxacarb and chlorantraniliprole based products. However, there are some significant differences between activity within the plant; Indoxacarb for example controlled some large larvae, but those further into the leaf whorl were less well controlled, compared to acephate for example.

Big variations in the residual activity of the different products is also being seen, which is often harder to detect in the field as it can be confused with a sudden decline or rise in pest activity. Guidelines and actions from our ongoing Fall Armyworm Insecticide Sensitivity trials will be available to agronomy clients as the work progresses.

FAW insecticides under test 2019  


Flubendiamide 28
Indoxacarb 22
Acephate 1
Emamectin benzoate 6
Pyriproxyfen 7
Lufenuron 15
Abamectin + chlorantraniliprole 6 & 28
Lambda-cyhalothrin 3
Methoxyfenozid 18
Spinetoram 5

Prilled Lime in Potatoes

All of the potato leaf samples that I see are low in calcium. Last October we set up some trials using prilled micronized lime in-furrow to see if we would rectify this. One of the challenges was placing the lime sufficiently below the seed tubers so as to avoid raising the pH around the developing crop and causing potato Scab (which is unlikely given the small quantity of lime, but nonetheless is a risk when liming in a rotation close to potatoes).

The results back then in February looked interesting, with slightly more tuber numbers per plant, but no measurable increase in yield. So we ran the trial again this season, on a pH 5.3 site with low calcium, applying 250kg/ha of prilled lime below the tubers.


The Hutton Institute Potato Size app is extremely useful for potato farmers to measure the size distribution of their crops quickly and accurately as I did in this trial. Download it for Android or iPhone.

There was no difference in yield (the trial was replicated 4 times for accuracy), with both the prilled lime and the untreated yielding 24.5 t/ha in the variety Panamera. Interestingly there was a very slight but visible increase in potato scab, despite the lime prills still being intact when we harvested. The leaf analysis showed no increase in Calcium either.

Next season’s potato work will focus on Phosphate and indeed Potash availability; two major nutrients that often show up in leaf analyses and visually in crops across the country.

Thanks to Kisima Farm for providing the crop to carry out this research on.

Center of Excellence for Crop Rotation Agventures

Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the futureof how we feed the planet. Agventure Ltd set up the Center of Excellence for Crop Rotation to help farmers diversify cropping systems and introduce techniques which have a long-term outlook to improve soil health. The Center of Excellence for Crop Rotation works extensively with Crop Nutrition Laboratory Services Ltd (CropNuts).

Till next time,

Happy farming,


David Jones

About David

David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.