Sowing Soya into Rye

Following research at the Rodale Institute, I wanted to test the possibility of creating straw mulch on a field scale by means of rolling down a cover crop at flowering with Rodale’s Moyer design of roller. Its unique feature is chevron shaped bars; the idea being that they roll down the cover crop without cutting through the stalk – what often happens with straight bars. If you cut through the stalk the plant will come back again. If it’s rolled flat and the stem damaged during flowering, it continues to try and supply the flowers until its energy is used up.

Initially I went for single species cover crops because there was no reliable information with regard to the flowering period of the cover crops in question in my region. Thus I couldn’t be sure that a mixed species cover would be in flower at the same time and therefore able to be killed by the roller.

The field destined for Soya was sown to a Forage Rye, chosen for its early flowering and that for Maize sown to Vetch, again a variety selected in the hope of early flowering. In each field I disced part of the cover crop in early spring and sowed the soya and maize conventionally into a prepared seed bed, followed by inter-row hoeing and tine weeding.

In the economic analysis I include the cost of cover crop seeds in both systems given that there is a need to protect and improve the soil in winter regardless of the seeding method the following spring. It was interesting to note that the rye, even after discing, had impressive allopathic effects in the soya that followed.

Rye in February. It was sown on the 30th October at 160 kg/ha.

Rye in April. 4 or 5 weeks before the intended sowing date for soya, it’s not looking promising.

Rye in May. Signs of flowering but development stunted in many parts of the field. The rye in the Rodale experiment was 1.80m tall. I’m tempted to abandon the experiment, disc it up and sow into a prepared seed bed. But another summer of cultivations and bare earth between the rows would only further damage the soil and reenforce the reason why development is poor in the first place. Decide to wait.

22nd May. Impressive growth in the last 3 weeks but still large areas where the coverage is very light. The mown part in the foreground is part of the ‘control’ area where a convetional seed bed will be prepared.

The Rodale roller in front, Sola seed drill behind with leading cutting disc and row cleaners.

15 June. Soya emerging through the rolled rye grass.

Soya 23rd June

Soya 15th August

The ‘control’ area after second inter row hoeing 27th July

Foreground – soya in rolled rye. Background, soya in prepared seed bed. The latter is more developed.

14th September. Soya in rolled rye to the right, prepared seed bed to the left. In the end there wasn’t much between them.

Agronomically, all the advantages of protected earth were evident. Humidity retained, temperature regulated, visible soil life much more abundant. There was signficant reduction in soil compaction – the 10 passages in the control section reduced to two in the rolled rye, sowing and harvesting.


 Soya in RyeSoya Control
Yield (tonnes)2.602.90
Sale price (620 €/tonne)1612 €1798 €
Production costs627 €1054 €

Based on the official price list for field operations

PRODUCTION COSTSoya in Rye - €/haSoya control - €/ha
Rye seeds9090
Soya seeds & inncoulum240240
Rye sown with Claydon drill5757
Rolling & sowing of Soya60
Mowing Rye51
Rotary hoe60
sowing of Soya42
Tine weeder29
1st inter row hoeing55
Tine weeder29
2nd inter row hoeing55
Tine weeder29
3rd inter row hoeing55
Manual weeding of Datura (toxic)30


The rye didn’t sufficiently protect the soil from winter rains. As a result the soil surface was compacted. In my opinion this meant the soya had difficulty in developing , partly due to difficulties of root penetration but also due to a lack of oxygen to feed the soil life required for its symbiotic relationships. Perhaps this is why, due to the persistant humidity under the rye and with it a gradual opening of the soil, this soya eventually caught up with the control. To improve soil protection I’m going to include some vetch with the rye next time. Now I know they flower at the same time and therefore can be rolled down together. I’m also going to add some structural radish at the same spacing as the soya.