Managing a living mulch with maize for soil protection and crop health

Summary

In this field lab Andy Gray, a farmer in mid Devon, is keen to trial different techniques of managing a clover living mulch under his maize crop

Growing maize is often associated with soil erosion and runoff.  This is partly because it is usually established using heavy cultivation, and harvested late in the year when the weather is often wetter.  It is best practice to establish an overwinter cover crop to protect the bare soil after harvest, but this does not protect the soil for the rest of the year.  There is often a long period when the soil is bare, especially whilst the maize is establishing, and immediately after harvest while the cover crop is germinating, leaving it open to erosion.

The benefits

A perennial, clover-based cover crop, or living mulch, should:

• provide year-round ground cover in the maize fields, protecting the soil from erosion and nearby watercourses from nutrient rich runoff.
• provide nitrogen to the crop, (through N fixing) thereby reducing the need for synthetic fertilisers.
• Reduce the annual weed burden within the maize crop
• Provide grazing immediately after the maize harvest without the need to wait for the cover crop to establish
• Increase soil organic matter and soil carbon storage 

However, maize is a very uncompetitive crop, and it is generally thought that a living mulch would reduce maize growth and therefore yield.

By trialling different methods of managing the living mulch, Andy hopes to suppress the living mulch long enough for the maize to establish, but still maintain the year-round ground cover.

Trial design

The trial will last 3 years.

Year 1: Andy will undersow his maize crop with a clover cover crop at the 3-leaf stage of maize growth.  Any gaps in the cover can be reseeded after maize harvest. Baseline soil carbon levels have been captured as part of a separate project

Year 2: Before maize drilling the plots will receive different treatments:

1 – heavy grazing with sheep to reduce the clover to ground level

2- herbicide treatment to knock the clover back but not kill it

3- control (no management)

The maize yield will be measured using a weigh bridge at hearvest

Years 3 & 4: repeat

At the end of the trial samples will be taken of soil organic matter and soil carbon.