Today’s issue of #ThinkAgronomy tackles main Agronomy challenges that crop up during planting and during the onset of the rains which is being experienced in most parts of the country.

Fall Armyworm

Following the sporadic rain over the past two weeks, Fall Armyworm larvae have appeared rapidly. Do not be complacent; spray as soon as the first larvae are seen, and assume that you will follow up 7-10 days later with a different mode of action (get the next spray in stock, ready to go).

I have discussed previously the merits of mixing two active ingredients at a reduced rate (as with the many co-formulated products on the market). However in a prolonged season of Fall Armyworm hatches and with limited modes of action available this inevitably leads to actives being used more than once, increasing the selection pressure and risk of resistance development.

Fall armyworm larvae

Precision Farming Compatibility

Precision Farming is a wonderful way to save on input costs and push the yield in different areas of the field as you see appropriate.

For medium scale farmers with their eyes on low-cost precision farming however , one of the main barriers is getting the various machinery to talk to each other. A group of machinery manufacturers including Agco (Massey Ferguson, Valtra) Pottinger, Krone, Amazone, Grimme, Kuhn, Lemken, Rauch, Topcon and Horsch have got together and launched Agrirouter to enable different formats of Variable Rate application plans to be transferred between machinery.

If you perhaps have an older Amazone fertiliser spreader and a Topcon box in a Massey Ferguson and struggle to get them to talk to each other with Isobus, farmers can register for free with Agrirouter.

You can upload a variable rate plan from a range of sources, then select what machine you have and either download to a memory stick or send it to the rate controlled in a format that the spreader / sprayer etc will understand.

Registration is free, and if the data exchange does work the cost is around $30-40 per year depending on how much you use the system.

Late planted wheat

As we approach the middle of May and the prospect of a wet October harvest become a real risk, should you be looking at different wheat varieties if you do decide to plant wheat?

This is an important question in many areas of Kenya, and depends on local rainfall patterns and the options available.

At present the variety Eagle 10 is the main alternative – provided growers have seed they can access – which is easily 10 days faster than the latest maturity varieties such as Hawk and Kwale.

In the grand scheme of things 10 days is not a great advantage, particularly given that Eagle 10 has yielded around 10-12% below the likes of Kwale, Korongo and Wren and around 20% below Hawk and Robin in our trials.

When you could set your clock by the arrival of the rains in years gone by, 10 days might have been valuable, but on a 4.5 t/ha (20 bag/acre) crop this will cost the grower around 14,000 Ksh. There is also the argument that Eagle is not always the easiest variety to market.

I would always suggest that assuming the crop does not sprout, bushel weight is the most important factor. In this case, avoid low bushel-prone varieties such as Eldo Mavuno, Baraka and Hawk and go for a red wheat with a high Bushel like Robin or Kwale.

Why are Kenya’s Maize planting populations so wrong?

maize populations

Across the country, thousands of small and large scale farmers alike have planted maize at around 60,000 seeds/ha and hoping to achieve stands of 50,000 plants.

Of all the things that I have disagreed with in our agronomy, this is number one. Take a look at where we stand in comparison to other major maize producing countries:

  Average yield Established plant populations
France 7.6 t/ha 34 bags 75,000 – 100,000/ha
Germany 9.6 t/ha 43 bags 70,000 – 95,000/ha
United States 10.9 t/ha 48 bags 85,000/ha
Chile 12.0 t/ha 53 bags 100,000/ha
Ukraine 8.0 t/ha 35 bags 70,000 – 100,000/ha

Of course the major detriment of pushing plant populations too high is the risk of lodging. Our local varieties, being bred for height (with the attraction being for livestock fodder after harvest) naturally exert more leverage on the roots and are hence more prone to falling over.

Part of this undoubtedly results from the use of crosses with weak inbred male lines and hybrid parent; cheap and abundant seed production but more variable plants which are unpredictable when planted at ‘proper’ plant populations. Three ways have also been an easy way for breeders to add in characteristics late in the game – like taste and sweetness. 80% of varieties in the USA for example are single cross hybrids, which produces much more uniform plants.

Producers in the US commonly plant 100,000 seeds per hectare now – a trend that has been on the rise over the past 10 years as planters improve seed placement and the uniformity needed for a tight stand. Uniformity of hybrids, and improvements in planting accuracy have allowed them to do this.

But is the guidance of 50,000 plants/ha appropriate for all of our varieties? We have four trials in the ground this year in Nakuru, Eldoret, Rumuruti and Timau to look at the performance of over 30 different varieties at both conventional and higher seed rates. Watch this space….

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.