Managing maize stubbles over winter

Published 23 October 15

With winter soil losses from roughly cultivated land reduced to 1% of that of bare maize stubble, good management over the winter period is crucial to minimising soil erosion and nutrient loss. Dr Debbie McConnell, AHDB Dairy R&D Manager, takes a look at the options for cultivation this winter.

For maize crops, increasing machinery sizes, coupled with harvesting at a time of the year when soil moisture levels start to rise, can present a considerable risk of soil compaction. Recent AHDB Dairy research has shown that soil compaction has significant negative effects on greenhouse gas emissions, soil biology and silage yields in the following season.

However, short-term soil compaction also increases the potential for surface runoff generation, by reducing the number of macropores or large air pores in the soil, which are regularly employed as conduits for water flow during the winter months or at times of heavy rainfall. This can result in the loss of valuable soil and nutrients through erosion.

Below average rainfall levels over recent weeks have meant that soil conditions for maize harvests this year have been good. But with harvesting well underway across the country, it is important to act when conditions are good to minimise any issues with soil erosion.

Fields with higher risks of surface runoff and soil erosion should be prioritised for activity immediately post-harvest. This could include poorer draining fields, those with steep slopes or fields which are close to rivers, streams, roads or buildings.

There are two possible options for managing maize stubble over the winter months to minimise any negative impacts of soil compaction:

  1. Establishment of a cover or autumn crop
  2. Rough cultivation

Sowing with an autumn crop or a cover crop such as ryegrass, over the winter period is an effective way of curbing soil erosion and surface runoff. A cover crop also helps to capture any excess soil nitrogen that has been mineralised over the warm summer months. For most, cover crops are difficult to establish this late in the season, however, rapid establishing grasses such as Italian ryegrass or Westerwolds, may be an option for some in areas where good autumn growth is common.

If, however, a following crop or cover crop cannot be established after maize, using a heavy cultivator is advisable. This loosens the top area of soil creating greater pore spaces between soil particles, which can transfer rainfall down through the soil profile. It also increases the surface roughness of the soil, slowing down any surface runoff and allowing more time for it to infiltrate into the topsoil.

Recent research completed by Rothamsted Research has shown that compared to bare maize stubble, cultivated soil had significantly lower surface runoff (Figure 1).

Figure 1: Effect of post-harvest treatment on surface runoff, soil and phosphorus loss from maize fields.

 

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When roughening the soil surface on maize stubble it is not necessary to cultivate the whole field, a few strips running across the field slope will break the momentum of surface runoff flowing downhill. However, these may lose effectiveness over the winter months therefore adding strips to the uphill side of these may be beneficial, but it is important to get the right soil conditions to complete this cultivation. Re-working cultivated strips is not advisable during the winter months.