Companion and catch cropping after vining peas: Impact on nitrate leaching losses

Background

Growing peas is associated with higher-than-average nitrate leaching losses after harvest. Establishing a catch crop early (i.e., end of June) after vining peas and before drilling winter wheat can be effective at reducing nitrate leaching losses. However, less is known about the impact of companion cropping.

The main objectives of the project were to determine:

• the impacts of contrasting over-winter ground cover treatments on nitrate leaching losses after vining peas
• the impacts of catch and companion cropping on the nitrogen fertiliser requirement and the yield of the following winter wheat crop.

The project was funded by Anglian Water with the seed mix kindly supplied by Kings Crops. Analysis of biomass was carried out by Frontier.

Results

Overwinter nitrate leaching losses from both the stubble and catch crop were high at 120 kg NO₃-N/ha. It was found the companion crop reduced losses by 50% (to c.60 kg NO₃-N/ha).

On the stubble cover treatment, nitrate-N concentrations peaked by mid-December (max. c.50 mg NO₃-N/l). The catch crop treatment nitrate concentrations continued to increase throughout the measurement period.

In contrast, nitrate concentrations on the companion crop treatment remained constant at c.18 mg NO₃-N/l.

As a result of this study, we can conclude:

• ground cover treatments had no effect on the nitrogen fertiliser requirement or yield of the following winter wheat crops
• initial results suggest that establishing a companion crop, in August, following vining pea harvest can be effective at reducing nitrate leaching losses while having no detrimental impact on crop yields.