Skip to content

Why Patience is the Key to Better Crops and Soils this Spring

23 February 2024

This article is produced as a part of the FAS Crops & Soils Bulletin. Subscribe now to receive the full report in your inbox monthly.

The extremely wet autumn and winter has caused waterlogging of soils and in some cases seen water lying in fields for prolonged periods of time, particularly following late harvested crops such as potatoes. It has also meant that ploughing and other winter tasks have fallen behind where they normally would be. It is vital that growers resist the temptation to try and farm by the calendar and instead, be patient and wait for the soil to be ready.  

How to Identify if Your Soil is too Wet

 As a rule of thumb, if a handful of soil can be easily moulded into a ball, then it is in a plastic state. In this condition, soils are very vulnerable to compaction and structural damage. It is also important to note that where soil structure is already compromised and compaction is present, then ploughing these wet, damaged soils may be a case of “out of sight, out of mind” and, while it will bring a workable layer to the surface to enable a tilth to be made to sow the crop,  it only creates a wet, cold anaerobic layer under the surface which will inhibit rooting and crop development.  

Why Must We Avoid Compaction?

Ploughing and working wet soils can also create its own compaction and do more harm than good. With a good healthy soil typically being made up of 50% mineral and organic matter, 25% air and 25% water, compaction essentially squeezes the air and water (or the life) out of the soil. In a good soil, roots can easily work their way through soils as pore size is often larger than the roots themselves, in a compacted soil, pore size is much smaller mean roots find it much harder to grow due to the increased mechanical resistance. This results in much poorer root systems and crucially less uptake of vital crop nutrients and water.  

These soils are also much more predisposed to becoming anaerobic and this can lead to denitrification, which see the loss of soil nitrogen as it turns into nitrous oxide – a key greenhouse gas.   

A well-structured soil can also have better water holding capabilities whereas compacted and poorly structed soils are unable to cope with heavy rainfall, being more susceptible to losing nutrients and causing pollution from erosion and run-off. These compacted soils will also be much more solid and harder to work. 

How to Investigate the Condition of your Soil

Some soils will be damaged already so it is important not to exacerbate the issue by creating more damage. Farmers should be prepared to get their spades out and dig holes to see what and where the problems are - are the problems simply due to too much rain, topography or soil type or is there something fundamentally wrong- is there compaction and how deep is it? One method for assessing a soil could be by conducting VESS tests or even using a penetrometer and gauging resistance at different depths.  

Remember a good soil should be porous with fairly small aggregates and have a good earthy smell and even a good number of worms. A poor soil will have large, angular aggregates with few pores, have a sour smell and few worms. 

How to Avoid Compaction

Apart from working soils at the right time, farmers and operators can mitigate compaction in several ways. Look at tyres – can you reduce tyre pressure when conducting field work. Reducing the pressure will increase the footprint and spread the weight across a bigger area, with another alternative being changing to wider tyres. In addition, less wheel slip will occur resulting in more efficient operations. Cultivations should only take place as deep as absolutely necessary. Going too deep, particularly in a damaged soil will only dredge up that cold wet layer to the surface, meaning seed beds will be harder to make and, in many cases, will be far from ideal, compromising crop establishment. Time should also be taken to ensure machines are set up properly.  This can help minimise the number of passes and makes best use of time and fuel. 

Finally, when soils have been damaged either by wet weather or by machinery it can be easy for farmers to look to metal to help re-invigorate the land. It is important to remember that weathering through natural shrinkage and expanding can also help make inroads to restructuring a soil. Roots can also play an important role, and getting a crop growing and letting it establish a good deep set of roots can really improve the structure of a soil. By being patient and working the soil when it is ready, growers give themselves the best chance of growing a crop that is both profitable while also helping their soils recover.  

 

George Chalmers, SAC Consulting

Sign up to the FAS newsletter

Receive updates on news, events and publications from Scotland’s Farm Advisory Service