Very often we talk about the ideal sowing or planting window for crops. There is without doubt an optimum for every crop and region – within the limitations of what the weather might do – but too often we view this in a perfect, utopian farming situation where weeds in particular are not an issue.

This year I have seen some very impressive results from planting crops in what would normally be considered ‘out of season’ where Brome grass is bad. We should not be surprised at this, as planting on 1st April or the last week of September every year selects for Brome populations which have a dormancy to help them germinate at the time when we plant and are hence most likely to survive and reproduce.

This is no different to how herbicide resistance develops over time, however planting windows are something which is in our control. The first prize is to plant a break crop in this window such as Canola so that herbicides such as fluazifop and propaquizafop can be used to kill a large percentage of the Brome in the seedbank.

Second prize is to move the planting according to the rain, so that you either beat the Brome while a large percentage is still laying dormant by planting early, or delay planting to allow it to germinate and benefit from a stale seedbed. With a fast variety and much less grassweed pressure the yield losses can sometimes be minimal.

One of the key factors I impress on growers is the need to be flexible, and to be clear about what your limiting factors are. Optimum planting dates in a fantasy world without grassweeds is not a limiting factor for many farms!

Also consider the best conditions for pre emergence herbicides – moisture seeking can help plant a tough wheat variety such as Troy get established before the Brome, or a later crop such as Eagle 10 or Brambling can still do well when planted just as the rains start when conditions are perfect for pendimethalin / flufenacet.

Key lessons on Stem Rust

After 10 trials across the country over the last 3 season, there are some very clear lessons emerging about Stem Rust control in Wheat. Why this simple work has not already been done baffles me, but at least we now have some clear guidelines.

Spot the darker untreated plots in the Nakuru fungicide trial which have been hit hard by Stem Rust.

Firstly, know your variety. This is the main defence, and in our trials in Nakuru, Hawk, Korongo and Robin all lost around 50% of their yield – this also helps you realise how much $$$ is at stake and why fungicide are good value.

Secondly, start early but keep the cost down. You never know when the weather or a sprayer breakdown might prevent you getting into the field to spray. I tend to begin with epoxiconazole at early stem extension because it has fair activity on Septoria and Yellow Rust too.

Always remember that later planted crops are exposed to inoculum earlier in their life so need protection earlier. Robin with Rust pustules at Growth Stage 31 is not good news.

One of the biggest risks with Stem Rust is running out of protection at the end, before the crop has matured – this is often where yield loss occurs in my experience. I find it helps to work backwards from when the crop is almost physiologically mature to time the sprays effectively.

The Blue bars show how a selection of various varieties performed against Robin with fungicide. The Orange bars show how they performed without fungicide, when Stem Rust was the main disease.

The best combinations give 4 weeks protection at the very most in the highest pressure situations, plus a week before the crop is mature when it is too late for damage to occur. In this case the final spray needs to be timed 5 weeks before the crop is mature, so when the grain is at soft cheese / dough stage.

Back 3 weeks from this to be secure in keeping the disease out takes you to just about ear spray timing for Fusarium, but do not let the interval stretch beyond 21 days if possible, 28 at the very most.

Some low Fusarium risk varieties in low Septoria situations can tempt growers to spray between Flag Leaf emergence and early flowering. This is the worst situation possible for Stem Rust control, as it means that the spray intervals afterwards will inevitably be longer.

Do not lose sight of other diseases however, and more importantly crop health and nutrition – we invariably see responses to foliar micronutrient applications where the plant appears healthy but has a very slight deficiency.

Foliar copper plays a very important role, and not for its fungicidal effects – much work has been done showing the importance of copper in plant health particularly in respect to Stem Rust resistance.

Pea trial lessons 2019

Peas should be a major crop in Kenya as a healthy, nutritious food for the consumer and a great break crop for the farmer which can be very profitable. With seven Pea variety trials harvested already in 2019, here are the key lessons to benefit from the crop.

Variety Bagoo shows very high yield potential for the third season in a row. We have now seen first-hand that they will hit 5 tons/ha on soils around Nakuru, and this is without inoculant! I cannot wait for the season’s trials to push them even further! This variety is current in National Performance Trials.

Seed rate should be 90-100 seeds/m2, and narrower rows help crops stand and compete against weeds, which means lower harvest losses but most importantly less pods and stained peas on the deck – quality control.

A full fungicide program is still required, the core of which should be multi-site inhibitor fungicides.

Lime is one of the few statistically significant yield responses in the nutrient trials on most soils.

Inoculation with Rhizobium works in virtually every trial we have done, but may take a few pea crops through the rotation to build up levels in the soil

Pod sealants work. The independent data in Europe supports this, and our own experience in the field reinforces this. On farms with low clearance sprayers an early application of Pod Sealant two weeks before desiccation can also help lay the tramlines down and ‘prepare’ the crop during the later desiccation pass to minimise losses.

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,


Barley farming in narok kikuyu laikipia eldoretAbout 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.