Nutrient status and topography

Before my journey to south Brazil I visited one of the Embrapa research institutes in the Cerrados region. They are similar in terms of their research to NIAB in the UK, but each region focuses on the crops and rotations specific to that area.

The soils in the Cerrados region can be naturally low in phosphate and at Embrapa I met with Djalma Sousa who had years of in-depth, long-term trials looking at improving phosphate levels and also the effect of different levels of phosphate application linked with different tillage systems.  The  depth of his soil knowledge was phenomenal and almost too much to take in, but he stressed how quickly soil organic matter could be degraded and that low cation-exchange capacity led to higher rates of organic matter decomposition.  In some of his trials there was better fertiliser efficiency with increasing organic matter levels, especially under a no-tillage regime and there was little difference between yields of placed or broadcast fertilisers when P levels were adequate.

No Phosphate

Above: No prizes for guessing which plot has had no phosphate applied in the last 10 years!

I’ve mentioned rotational balance before, but this came up again in Djalma’s trials where a cover crop in a no-tillage system with millet as part of a balanced corn rotation was producing 20% more yield than conventional cultivations with no covers in continuous corn.  He also highlighted another example of the synergy with livestock and their sequence within a crop rotation system where everything centres on organic matter as the key driver.  Djalma told me there can be up to 1 tonne per hectare more carbon sequestration under no tillage compared to a conventional system and as the soil balances out there are better fertiliser efficiency rates, allowing for better optimal fertiliser usage.

After a brief one-day break, I ventured to the far south of Brazil. The flight from Rio to Sao Paulo was late and meant I landed with 10 minutes to go before the one and only connecting flight to Passo Fundo took off.  I had a close call in November with a connecting flight in Singapore, but for this one, I didn’t even leave the tarmac of the airport!

This part of Brazil has some of the most stunning countryside I have seen on my travels: beautiful rolling hills, green landscapes and perfect blue skies – it really was breathtaking.  The fascinating thing when you start heading south through the Parana state compared to the Mato Grosso is that they actually get a winter here, including frosts and sometimes snow and certainly the mornings started off 10 degrees cooler, so there is a difference in  the cropping patterns.

Farm sizes are a lot smaller – some only 50 hectares, but more diversified with livestock, and wheat features more heavily in this region as part of a corn or soya based rotation.  I mentioned Sebastiao Conrado in my previous blog and how in the 1970s they faced the challenge of dealing with erosion and it became patently clear with the gradients and topography of what they had to deal with.

Nestor Cavali

Above: Nestor Cavali in a perfect field of no-till soya beans and the local topography in the background

High levels of rainfall and cultivated ground were not a good combination and that was when no-tillage started to take hold. Contour banks are still used in some areas to reduce the erosion risk, but some of the best no-tillers require them less nowadays.

Black oats or vetch were the cover crop of choice and it was stressed to me how important it was to maximise the ground cover with them. Applying fertiliser to get the rows closed not only helped with establishment, but increased the competition against weeds and, coupled with their aggressive root system, could help with compacted soil layers.

Nestor Cavali was another impressive grower I met, who spoke about the problems with surface crusting associated with cultivation before this was eliminated under no-tillage. His organic matter levels were 5-6%, compared to a regional average of 3%.  His soils had stabilised to the point that he no longer required the contour banks due to his excellent management.  Nestor felt investing in the winter cover crop was very important, in terms of establishment and getting dry matter levels up to 6-8 t/ha, and that cover crop desiccation should be at least 40 days ahead of planting to ensure that the decaying cover is complete. He also spoke of fertilising the system rather than the crop.

Nestor was a firm believer in investing well in the crops he grew, commercial or cover crop and this shone through in the yields he was achieving. In dry seasons the drop off in performance would be around 10-15% at worst from their base levels which were very impressive as they were.  Residue was another top priority and the better the level of residue would help reduce the likelihood of compaction, and he favoured using a strong rooting cover crop rather than machinery to deal with it.  It was vital that the soil remained covered at all times to shield it from hot weather and, as a barrier to pounding rain, it was crucial to get the cover crops established as soon as possible after harvest.

Residue Above: The level of residue & quality of soil in one of Nestor Cavali’s fields.

Nestor had reasonably high clay content, and his management over the years had been spot on: large amounts of surface residue, a fantastic friable soil layer and no evidence of compaction were clear to see. He achieved some of the most wonderful, even crops I had seen anywhere on my travels.

Next time: Next stop Argentina in the final week of my travels.

RussellMckenzie

RussellMckenzie

Russell McKenzie farms 750ha on predominantly heavy clay on the border between Cambridgeshire, Bedfordshire and Northamptonshire. He grows seed on contract as well as soft and feed wheat, and his usual rotation is wheat, OSR and spring beans. A Nuffield Scholar, Russ has been researching direct drilling in extreme weather in 2013 and 2014.

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