The first question growers ask about forage pea is usually the timing: autumn or spring? A single date is hard to give, because in forage pea the calendar follows from two things at once. The first is the growth habit of the variety: a winter type is selected to be sown in autumn, while the calendar of a spring type falls in spring. The second is the severity of the region’s winter; the literature points to autumn sowing in mild regions and early spring sowing in harsh continental ones. Assas is listed as a winter type with “very good” cold tolerance on its data sheet, and its sowing window falls in autumn: from October to mid-December. In this article we look at what changes inside that window, at sowing depth and seed rate, at the mixture ratio research points to, at the balance between yield and quality at cutting, and at what the crop leaves in the field after harvest.
Autumn or spring: the variety’s habit and the region’s winter
Forage pea is a cool-season crop; it does not ask for high temperatures to germinate, and agricultural publications point to a daily mean temperature of 3.5-9 degrees Celsius for sowing. Autumn sowing is possible for that reason. What sets the limit is the lower end of the scale: a field sown before winter has to spend the cold period outside, and it can only do so with a cold-hardy variety. Publications note that forage pea tolerates short frosts and that there are varieties able to withstand minus ten degrees in their early growth stages. Where the winter is very harsh the general recommendation is still early spring sowing, that is February-March; in mild and transitional regions autumn sowing is preferred.
Assas stands on the winter side of this distinction. Its data sheet gives the growth type as winter and the cold tolerance as “very good”; the variety was registered by TTSM in 2018 and its breeder is Agri Obtentions. It is also flexible about the land: lowland, semi-lowland and dryland fields all come into consideration. With those two features together, autumn sowing settles comfortably into the rotation in regions where the field is freed after the cereal harvest. Where winters are severe the decision is taken field by field; if spring sowing is intended on such a field, looking for a spring-type variety is the sounder course.
The difference between sowing early and sowing late
The autumn window on the data sheet is close to two and a half months: from the beginning of October to the middle of December. One of the main reasons for that width is the climatic difference between the regions of Türkiye, another is when the field is freed by the previous crop. Where the cereal harvest and the clearing that follows are completed early, the early end of the window can be used; where the field is freed late, sowing moves into November or even early December.
The two ends of the window do not give the plant the same thing. In an early-sown field the crop enters winter more developed and finds time to tiller; in Assas tillering reaches up to 18 main stems, one of the main features that raise the forage taken from a unit area. At the late end the time left to the plant is shorter, so the cold tolerance of the variety weighs more heavily. The data sheet gives mid-December as the end of the window; for sowing after that date we have no recommendation.
On the technique side the figures are fairly clear. Publications give a sowing depth of 3-5 centimetres and a row spacing of 15-20 centimetres; drilled in rows, 12-15 kilograms per decare is enough, while broadcasting raises the amount to 15-20 kilograms. The Assas data sheet also gives 12-15 kilograms per decare for a pure stand, which matches drilled sowing; the extra seed in broadcasting comes from the method’s lack of control. On fertiliser the advantage of being a legume shows: publications suggest 3-5 kilograms of pure nitrogen per decare together with a similar level of phosphorus at sowing, and no further nitrogen afterwards, because the plant begins to fix its own nitrogen in time. Where a legume enters the field for the first time, seed inoculation with Rhizobium leguminosarum is also among the recommendations; our seed is not supplied inoculated, and growers who prefer inoculation carry it out themselves.
Pure stand or mixed with a cereal?
Forage pea can be grown either on its own or mixed with a cereal, and the data-sheet rate is given separately for the two cases: 12-15 kg per decare pure and 10-12 kg in a mixture. As the pea’s share falls in a mixture, so does the seed that goes on a decare. The mixture described most widely in practice puts 6-7 kilograms of cereal seed next to around 12 kilograms of pea.
The reason for mixing has to do with the structure of the plant. Assas reaches 180-200 centimetres, with a sound, broad stem and broad leaves; a legume of that height stands more easily beside a cereal that supports it. The second reason is on the forage side: a legume ensiled on its own struggles because of its low sugar content, while the cereal in the mixture brings dry matter and the carbohydrate the fermentation needs. On the ratio there is research: in a trial published in the Journal of the Faculty of Agriculture of Çanakkale Onsekiz Mart University, testing forage pea against barley, oat and triticale at several ratios, the highest green and hay yields came from the mixture of 50 percent barley and 50 percent forage pea; the study recommends a 50:50 binary mixture of barley or triticale with pea. In our region barley or a triticale such as Ramdam comes to mind for that mixture. Our general approach to seed rates is set out in the article on how much seed per decare.
Cutting time: yield or quality?
In an autumn-sown Assas field the forage harvest falls at the end of April or the beginning of May, and the data sheet gives a window of 15-20 days after the first flower. Where to cut inside that window depends on what is expected from the field. A study carried out in Kırşehir between 2013 and 2015 and published in the Journal of the Central Research Institute for Field Crops cut a forage pea and oat mixture at three stages: start of flowering, full flowering and pod set. Hay yield reached its highest at pod set, while crude protein was highest at the start of flowering; in pure pea, protein was measured at 17.54 percent at that stage. In other words, the later the cut, the more forage leaves the field and the lower its quality.
The cutting decision is therefore tied to the intended use. Where hay is the target, publications point to the period between the start of flowering and 50 percent flowering; where silage is the target, the flowering stage comes forward. The same Kırşehir study, weighing yield and quality together, recommends keeping the pea share of the mixture around 50-60 percent and cutting at the start of flowering. Hay making brings one more detail: in legumes, leaf shatter during drying causes nutrient loss, and because most of the feeding value sits in the leaf that loss goes straight into forage quality. The smaller harvest and storage losses of silage are one of the reasons mixed sowing is preferred on the silage side.
What stays in the field after harvest
The account of forage pea does not close with the cut. Being a legume, it fixes nitrogen in the soil through its roots and the following crop uses that nitrogen; this is one of the reasons cereals so often come after a legume in the rotation. Completing the harvest at the end of April or the beginning of May also leaves the field room for a second crop in the same year, so the field is not locked into a single product.
The variety’s forage figures come from the registration trials. Assas came out 19 percent above the trial standard in green forage yield and 22.1 percent above it in hay yield. The data sheet gives a protein content of 18.49 percent and a dry matter digestibility of 121.3. On the health side there is tolerance to root diseases, and the seed is supplied treated against fungal disease; seed coming out of the bag needs no further treatment.
To return to the question in the title: in forage pea the sowing date follows from the variety’s habit and the region’s winter, and for a winter type such as Assas the window on the data sheet is the autumn period, from October to mid-December. The early end of the window leaves the plant time to develop, the late end a shorter preparation period; the choice between them is decided by the previous crop of the field and by the climate of the region. For growers who want to build the forage plan as a whole, our alfalfa and Italian ryegrass varieties sit at different points of the same calendar; the choice of sowing period in alfalfa we covered in autumn or spring. When the rotation of the field, the severity of the winter and the intended type of forage are shared with us, our agronomist assesses whether a pure or a mixed stand suits those conditions: +90 506 101 01 50. The full data sheet of the variety is on the forage pea seed page.