Adding evidence to decision making regarding cover and catch crops.

Project motivation and aims:
The use of cover crops and shorter duration catch crops is becoming more common place in UK agriculture. Many benefits of such practices are well demonstrated, for example; prevention of soil erosion and leaching of nitrate. Others coming to the fore much more recently are less well understood. There is now interest in adding carbon to the soil, for the long term and as a shorter term substrate for the soil biota. In addition, there is the concept of the "biological plough" in which plant roots create pores and fissures in the soil benefiting the whole soil system.

The cash crop may perform these functions, but most crop rotations include significant periods of time when the land is not occupied by a cash crop. At these times additional benefit may be gained from a cover or catch crop. This is often particularly evident in field vegetable production where planting and harvesting dates can be very variable. Cover and catch crops must display specific traits to be of benefit to the grower in different rotational positions and thereby justify seed and planting costs; compatibility with cash crops, strong root penetration, growth in low temperatures and light intensities and zero seed return.

Many companies sell seed for these purposes, often as pre-prepared species mixtures with marketing material showing multiple benefits. However, to date there is very little independently conducted peer reviewed literature to support decision making when selecting from the range of available mixtures. What research has been conducted has focused upon mainstream arable agriculture and associated planting and harvest dates. It is now proposed to study a broad range of candidate species to; provide evidence for growers to make decisions and identify selection criteria that seedsmen and plant breeders may consider when developing cover and catch crops.

Programme of research:
The research programme will investigate key traits influencing suitability of a cover or catch crop for different rotational contexts and quantify the benefits to cash crops. This will be done by investigating the physiology of potential cover and catch crops, the science of soils and the agronomy of cash crops with and without a history of catch and cover crops grown in the rotation.

Year 1 - An initial literature search will seek evidence to contribute to the selection of approximately 25 genotypes of potential cover or catch crop from a wide range of taxonomical groups. Physiological traits of interest include; the ability of roots to penetrate hard soils to depth, photosynthetic capacity in conditions of low temperatures and light intensities (i.e. over-winter), floral development (potential seed return and a weed problem), cold / frost tolerance, and the interaction between the two (floral initiation lessening cold tolerance). They will be grown in controlled conditions of soil layers of known penetration resistance where rooting to depth will be quantified.
Year 2 and 3 - The quantification of the benefits of cover and catch cropping will be addressed by studying the cash crop and the soil it is growing in with field experiments; changes in yield and or quality, growing costs, root development and soil physical properties will be quantified. Although the role of cover crops in protecting nutrients is well documented, the effects will be measured to allow a full understanding of the whole agronomic system.
Photosynthetic characteristics will be studied using Infra-Red Gas Analysis instruments. Techniques to remotely sense the soil drying front as cash crop roots develop will be used and soil samples collected for physical characterisation in the lab.
Year 4 - data analysis and writing. All investigations will be strongly supported by statistical advice on experiment design and data analysis.