3 PROGRESS TOWARDS THE 2000 FIELD PROGRAMME
The main progress towards the 2000 field survey programme has been in terms of site selection. There are two elements to this. The first is obtaining a description of the commercial management of the crops under study, to provide a basis for identifying a representative range of sites. These descriptions are provided below. The second element of this is the structure of the actual samples. As this process is ongoing at the time of writing, it will be reported fully in our next report.
3.2 Maize cropping in Great Britain
Most of the crop grown in the UK is grown as a forage crop because the climate is not warm enough for the food varieties. It is typically fed as maize silage to cattle in the winter as a complement to grass silage.
Maize is usually sown from late April to early May although sowing dates vary with soil and weather conditions, for example in the most southern counties the crop is typically drilled at the beginning of April when the soil temperatures are warm enough. The minimum temperature for germination is 10°C and seedling growth before 13°C is very slow so it is not adapted to cooler parts of the temperate zones.
Maize is usually grown on lighter soil types because of its ability to withstand drought reasonably well. These soils tend to get ploughed relatively late and are then drilled quickly after this. Harvest date depends on the variety that is being grown, generally the earliest varieties are not used as these have a significant yield disadvantage. The earliest harvests occur in the most southerly counties from mid August and the latest occur in the most northerly counties from the start of November.
Mean dry matter yield in the last five years of NIAB trials has been 14 t/ha. By contrast average yields of maize grown for human consumption are much lower at about 4 t/ha. Total UK production of maize according to MAFF statistics was about 100,000 hectares in 1999 compared with 97,000 hectares in 1998 and 109,000 hectares in 1997 (about 200 ha of this represents the small amount grown each year for human consumption).
In Europe, the northernmost barrier for the cultivation of maize is Southern England, the Netherlands and northern Germany. Elsewhere in Europe it is grown on a very large scale. In general the over 70% of the British crop is grown below a line from The Wash to the Bristol Channel. However with the introduction of newer, earlier maturing varieties more maize is now being grown in the North.
The average maize field size is around 4 ha. However, actual sizes will vary depending on geographic location. In general the Eastern counties have larger fields, around 7 ha, and in the west of the country fields tend to be smaller at about 3 ha.
The late ploughing of land for maize crops means that for many soil types farmyard manure (FYM) can be applied prior to the crop being drilled and thus over a long period if required. If this is the case little other fertiliser is applied. Where FYM has not been applied then artificial fertiliser is applied – typically around 200 kg/ha K, 150 kg/ha N, and 50 kg/ha P.
Pesticide usage on maize is normally restricted to a seed treatment, two applications of herbicide (usually two herbicides, using two products and two active substances) and sometimes an application of foliar pesticide. Weed control is in general achieved with a low dose of Atrazine although where maize has been grown continuously weeds do become resistant to this product and other contact herbicides have to be used, for example, Bromoxynil. In 1997 seed treatments accounted for 50% of all pesticide applications to maize, the most extensively used were Thiram (fungicide seed treatment, 42%), Methiocarb (molluscicide, 35%) Bendiocarb (insecticide seed treatment, 8%) and Anthraquinone (repellent seed treatment, 8 %). In 1997, Gamma-HCH was used on 85% of the insecticide treated area, and most usually applied to control wireworm or a combination of wireworm and leatherjackets.
In summary,
- About 70 % of sites are south of an imaginary line from Bristol to the Wash.
- Mainly on lighter soils.
- Most will use 2 applications of herbicide (most likely Atrazine).
- Insecticides or fungicide use will be low.
3.3 Spring rape cropping in Great Britain
The main spring-sown oilseed rape in the UK is a variant of Brassica napus L. (swede) that does not require overwintering to induce flowering. In the north and west of the range, Brassica rapa (turnip) is also grown as a spring oilseed crop. The two species are difficult to tell apart from a distance but can usually be distinguished by their morphology. These spring-sown oilseeds have a range of uses in food and cattle feed and as industrial oils.
Spring rape (like winter rape) has a place in cereal rotations as a break crop that permits, for example, grass weeds to be treated with selective herbicide. A range of varieties (see below) provide some flexibility in sowing and harvest dates. The growth of Brassica rapa is less sensitive to sowing date than Brassica napus. It usually matures earlier and is more tolerant of poorer conditions, so is a suitable alternative in wet years or if operations in the spring are delayed.
Sowing dates naturally vary with the condition of weather and soil, are typically around late March and early April, but can extend from late February to early May. Harvest dates range with a similar spread around early September. The duration from sowing to harvest for Brassica napus is therefore around 150 days, varying with weather and cultivar.
The mean yield of the spring sown varieties in NIAB trials was 2.8 t/ha, and the rolling five-year average 2.6 t/ha; mean yields on farms are likely to be slightly lower than these figures, though individual farms can achieve much greater yields.
As a spring-sown crop, spring oilseed rape is associated with periods of fallow and generally reduced input. The crop itself is a food source and habitat for a wide range of foraging animals including molluscs, insects, mammals and birds. The toxic properties of oilseed rape (swedes) and cabbages – caused by glucosinolates and related chemicals - have also been recognised for a long time. Modern cultivars contain a large variety of glucosinolates whose ecological effects are not well understood.
Spring oilseed rape is predominantly a crop of northern parts of the UK where its ability to grow in cool and damp weather provides the farmer with flexibility over soil preparation and sowing time. Spring oilseed rape occupied between 12 and 24% of the total oilseed rape between 1993 and 1998. However, around one third (28% to 38%) of this spring rape was grown in Scotland. Detailed maps cannot be given for England, as data for spring and winter rape crops are combined.
Although potentially valuable as a break for ‘cleaning’ fields, spring oilseed rape actually receives few chemical applications compared to most other crops. The proportion of the area treated varies substantially from year to year depending on weather and other factors. The main ingredients applied in Scotland are trifluralin as a weedkiller, glyphosate as a dessicant and Cypermethrin as an insecticide against pollen beetle.
Oilseed rape is generally grown in soils over pH 6. There are various recommendations for fertiliser, typically 75 to 150 kg/ha N (less for Brassica rapa) and a treatment of P2O5, both applied around sowing. Sulphur is listed in the pesticide surveys for Scotland as a fungicide, but is usually intended as a fertiliser. The main weeds are the typical, arable, spring-germinating broadleaves and some grasses. A range of chemical weedkillers is available to treat most weed species. In Scotland the proportion of the crop treated was 84% in 1998. Trifluralin, acting as a pre-sowing herbicide, was the main chemical applied as a weedkiller, used on 37% of the cropped area (22% in 1996). Also, the broad-spectrum herbicide glyphosate was applied to 40% of the cropped area as a desiccant. In 1998, 16% of the cropped area was not treated with any weedkiller or desiccant (41% in 1996). The Scottish survey in 1998 showed 75% of the cropped area was sprayed with insecticide. No molluscicides were used in 1998. Fungicides were applied to 21% of the cropped area (35% in 1996). Finally, all spring rape sown was seed-treated to reduce damage by fungi and invertebrates.
In summary, spring rape crops show
- a wide geographical range from northern Scotland to southern England, with little or no centralisation of sites;
- and about one third in Scotland, two thirds in England;
- include a range of intensity, defined by chemical inputs and also general management for diversity, with the balance away from the high end;
- about half will apply desiccant;
- most will probably spray one insecticide;
- will use only a few cultivars between them.
3.4 Beet cropping in Great Britain
Both sugar and fodder beet are variants of Beta vulgaris. Fodder beet is used as stock feed and is characterised by enlarged hypocotyls and crowns compared to other forms of Beta vulgaris. In England the name fodder beet refers to types with smaller roots and high dry matter content whilst those with round ‘roots’ (derived from the hypocotyl) and which stand out of the ground are mangolds or mangels. The main use of sugar beet is to produce sugar, although the tops are often fed in fields to sheep. There is virtually no ensiling of sugar beet tops now. Both fodder and sugar beet are biennial, whereas weed beet, which is widespread in fields that grow sugar beet, has an annual habit.
Sugar beet is grown predominantly in cereal rotations with over 80% of beet crops preceded by winter wheat. A range of crops may follow beet. However, most early harvested (September or October) sugar beet is followed by winter cereals whilst later harvested crops are usually followed by winter cereals, spring barley or set-aside. Fodder beet is grown on farms producing sugar beet and is also grown as stock feed on mixed farms. Sugar beet is grown under contract to British Sugar and is restricted to a minimum rotation of one year in three. Most rotations are between three and six years, although some can be longer. Little information is available (to date) on fodder beet rotations, but these are believed to be of the same range as sugar beet.
Fodder and sugar beet seed is treated with fungicides and approximately 70% of the sugar beet crop is also treated with imidacloprid on the seed pellet. Approximately 7% of fodder beet are treated with imidacloprid and all seed is treated with Tachigaren, Thiram and Mesurol. The optimum dates for sowing sugar beet are between 10 March and 10 April, although weather conditions may result in some being sown in the first week of March or delayed until late April or early May. Fodder beet on non-sugar beet growing farms is usually sown a little later, with most sown in April. Harvest dates for sugar beet range from late September to February, mostly before December. Most fodder beet is used on farm or locally and tends to be lifted in November. As a spring sown crop, beet crops are associated with periods of fallow in the autumn.
Sugar beet is grown predominantly in East Anglia (33% of National crop in Suffolk and Norfolk), but as far north as Yorkshire and south as far as Essex. The other main area is in the West, although there are some farms as far north as Ormskirk and a few as far south as Dorset, Somerset and Cornwall. Fodder beet tends to be grown in the south west, some northern regions, Wales, Scotland and throughout the sugar beet regions. Fodder beet will grow on most well-drained soils. Heavier soils are best avoided as it can be difficult to prepare a good seedbed, and wet autumns can present harvesting difficulties and produce high dirt tares.
Whereas the sugar beet growers may tend to have more unified advice provided through British Sugar, including the British Sugar Beet Review journal sent to all growers, and the fieldsmen employed by British Sugar, there is not an equivalent system for fodder beet growers. The average field size for sugar beet is 6.5 ha but there is a wide range and some fields may be as large as 40-50 ha. Currently in the UK there are a little under 9,000 growers and 180,000 ha of sugar beet is grown annually. Fodder beet is grown on around 10,000 ha and the average field size and number of growers is not known. It is expected that fields will generally be smaller than sugar beet fields.
Some sugar beet is direct drilled especially in the North on light soils. Where soil erosion and wind blow is a problem, barley cover crops may be sown to protect the emerging beet seedlings (currently less than 10% of the total area growing sugar beet). Nitrogen is applied in the spring and applications may be split applications, to a maximum N application of 120 kg/ha. Organic manures are used in some areas. The optimal pH is around 7. Acidic soils cause more problems than alkaline ones.
Herbicides are applied in programmes and mostly as mixtures of several active ingredients. Programmes may use one pre-emergence and / or a number of post-emergence treatments. Particular problem weeds are thistles and volunteer potatoes. Control options based on the relatively expensive product, Dow Shield (clopyralid), are needed to control these species. With the widespread use of imidacloprid in seed treatments on sugar beet (70% is treated with Gaucho) the need for insecticide treatments later in the season is much reduced. Foliar sprays against aphids (pirimicarb) are now only applied in less than 20% of the sugar beet crop. Some seed is primed for rapid and even emergence (on about 12% of the sugar beet area) using a system called Advantage, where the seeds are part germinated before pelleting. Other treatments applied at drilling include seed treatments of Force, which is a pyrethroid (tefluthrin), against soil pests and is used on 4% of the area planted. Sugar beet fields are treated with Aldicarb (approximately 10% of the National area) and carbamates are used on 15% of the total area. Approximately 60% of the crop annually is treated with fungicides. Where fodder beet is grown in the same areas as sugar beet the products used for weed, insect and disease control are likely to be largely the same, some as off-label applications registered for minor crops. In areas where sugar beet is not grown some of these treatments may be less easily available.
In summary, farms growing beet are:
- found mainly in arable areas of East Anglia, Lincolnshire, Yorkshire, the Midlands and South West
- on well-draining soil but not of the heavier types (ideal pH = 7)
- typically grow beet in the rotation, most likely after a winter cereal, but in not more than one year in three
- probably spray the crop with a number of herbicides on several occasions
- might apply glyphosate as a weed wipe against weed beet
- will probably have been drilled with imidacloprid treated seed (70% of sugar beet, similar levels in fodder beet grown in sugar beet areas, unknown in fodder beet farms in fodder beet areas)
The Consortium is treating sugar and fodder beet as a single crop, but with the intention of sampling reasonable numbers of both types during 2000, so that this decision can be reassessed before the 2001 plantings.
3.5 Overall progress on site selection
While concerns were raised about the availablity of sites at the February meeting of the SSC, we consider that at the time of writing the project is now well placed to deliver its planned work programme for 2000. We feel that we have an adequate range of sites for all crops in the study, both in geographic range and in intensity.
This situation represents a remarkable willingness for farmers to take part in a project that remains highly controversial. While we have not undertaken any formal survey, our impression is that farmers genuinely want to see whether or not GM crops affect wildlife, and they value being part of a formal experiment of such national importance. We are very grateful to them.
At the time of writing, site selection is between the stages of proposals being provided by SCIMAC to the Consortium, decisions being made on the acceptability of sites by the Consortium, and contracts being drawn up with the farmers by SCIMAC. Site visits to establish randomization have not yet taken place.
The next steps for all crops are the visits to randomize the treatments and to establish the locations of the sampling points. The initial sampling of the soil seedbank is also a matter of urgency.
Published 13 June 2000
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