Conservation Tillage

Is conservation tillage right for me?

The soil is undoubtedly a farm’s most valuable resource and is the foundation underpinning its production. Decisions that affect soil conservation and its state of health can have long term positive or negative impacts.

Every time the soil is cultivated there is a burst of microbial activity and oxygen levels in the disturbed soil increase. In the absence of large volumes of organic matter being incorporated through green-manure crops, this burst of microbial activity results in a flush of carbon dioxide and a corresponding net loss of soil carbon and organic matter from the soil. Production systems that rely on cultivating the soil multiple times each season can result in a significant loss of soil organic matter and productivity over time. Furthermore, freshly cultivated soils also have an elevated risk of erosion from wind and rainfall. For these reasons, we should always be mindful about the need to cultivate the soil.

So why cultivate? We tend to cultivate the soil for several reasons, in no particular order: • Reduce soil compaction • Aerate and warm the soil to enable earlier sowing to utilise more of the growing season • Prepare a fine seedbed to successfully establish the crop (depending on seed size) • Bury crop residues to mitigate pest and disease pressure • Incorporate fertilisers, green manures and (sometimes) preemergent herbicides • Because that is what we have done in the past and it’s what most other farmers do

Reduced or conservation tillage in its various forms is aimed at conserving or improving soil health, organic matter, moisture availability and drainage, whilst reducing input costs and either maintaining or enhancing crop yield and/or profitability. Two such systems that are gaining popularity in New Zealand maize production systems are no-till and strip-till (only cultivating the strip where the seed will be planted).

Besides soil conservation, one of the key drivers for conservation tillage is to reduce costs. Both strip and no-till systems have been shown to result in significant savings in fuel consumption and time. However, it is also true that no-till and strip-till systems tend to require a bit of extra effort and expense when it comes to protecting the crop from pests such as slugs, and this may offset some of the fuel savings benefits.

In no-till systems crops are sown directly into the soil with no prior tillage or cultivation operations. No-till cropping has been around for decades with over 104 million acres of maize produced using no-till in the USA in 2017. So, we know it works! FAR (Foundation for Arable Research) have been doing no-till work with maize for several years now and have found it to be as profitable as full cultivation systems providing the fundamentals are adhered to.

The thing with no-till cropping is that planting is often a little bit later to allow the soils to warm up . Timing is critical and soil moisture must be at optimum levels (think damp but crumbly, rather than sticky, smeary) for even crop emergence. Pest and disease control should be at the forefront of the programme especially slugs and hybrid disease tolerance/susceptibility but also weeds. It’s difficult to get a true fallow period to help with pest control and ensure the roots from pasture have rotted enough to enable adequate soil-tilth.

In terms of strip-tillage, this was pioneered in New Zealand back in the early 2000’s mainly on the East Coast of the North Island with some very positive results. As is often the case however, adoption is often slow unless there is a reason to change. With more and more pressure coming on farmers from all directions it’s little wonder there has been renewed interest recently and an increase in the number of contractors offering strip-till as an option.

Now before jumping in boots and all, it is worth considering that some soils are well suited to no-till or strip-tillage, whereas others may not be so favourable. That heavy, compacted, pugged or wetter paddock down the back of the run-off is probably not a good place to ‘test the waters’. On the other hand, those lighter textured or rolling paddocks prone to drying out and/or erosion when heavy rainfall strikes before canopy closure would be the ideal place to start your minimum or no-tillage journey.

As always, it often pays to seek advice before making any major changes to your operation and there is certainly a lot to consider when it comes to conservation tillage. Your contractor is a good place to start, or you could contact FAR who will be more than happy to answer any questions you may have and put you in touch with other growers with experience in conservation tillage.

Scott Shaw - Senior Technical Specialist