Seed quality and testing
Seed harvesting and drying
Pest damage
Disease and pest testing
Seed treatments
Sowing date
Plant population
Implications of plant population on crop husbandry
Soils and Cultivations
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Seed quality and testing
Beans are often sown during late autumn into cold, wet soils. They are extremely sensitive to compaction and waterlogging, which reduce root growth and can therefore influence water uptake in drought conditions. In poor soil conditions, seed quality is of great importance, allowing good emergence and establishment in often difficult conditions.

Bean seed is easily damaged during harvesting, drying and handling, and thus it is important to ensure the seed sown is of the best quality. Work at Nottingham University showed a 50% reduction in establishment in the spring of combine damaged seed compared with undamaged seed of the same seed lot¹².

Seed harvesting and drying¹³
Seed drying at too high a temperature can cause damage to the seed and reduce the quality. Guidelines for seed drying are outlined below:

Maintenance of quality during seed drying¹⁴
Equilibrium moisture contents of bean seeds at different values of relative humidity at 25^oC

Pest damage
Bruchid beetles bore holes in the seed, which allow sugars to leak out of the seed during germination and provide, encourage disease infection during establishment.

Germination and vigour seed tests
Germination measurements often bear little relation to field emergence since damaged seed which germinates well in the lab is prone to damping off diseases in cold, wet soils. Seed conductivity measures seed damage and is better related to field emergence. Conductivity measurements below 16 indicate healthy undamaged seed that should establish well in the field. Seed size is also a good indicator of seed vigour, large seed yielding 11% more than smaller seed from the same seed lots over 17 trials¹.

1. Conductivity test
Conductivity measurements are not a standard for beans although the test is routinely done on peas, requiring 100 g sample and taking 1 to 3 days to complete. Conductivity measurements will be conducted by NIAB although this is not a standard test and no interpretation of the results is offered. Research in Scotland, suggests that conductivity measurements below 16 indicate healthy undamaged seed that should establish well in the field, whereas seed with higher conductivity scores are more prone to damage from seed borne diseases and should not be sown into poor, wet seedbeds.

Figure 1. Bean seed quality [redrawn from data from c. Hegarty, 1977 J. Ag. Sci. (88) 169-73] Click here for a larger image

2. Tetrazolium test
The tetrazolium test is a rapid test used as a vigour score. It was designed for use on green beans and is currently also used on field beans. It involves soaking the seed in tetrazolium chloride, which stains the living areas of the seed red. It denotes area of mechanical damage or areas of the seed that may have been damaged by disease.
The test takes 1 to 3 days to complete and requires 150 g sample

3. Seed size
Seed size is also a good indicator of seed vigour, large seed yielding 11% more than smaller seed from the same seed lots over 17 trials¹.

Disease and pest testing
Standard seed tests for field beans include Ascochyta leaf and pod spot and stem nematode. Seed treatments are available for Ascochyta. Stem nematode results are indicated as either present or absent although more detailed scoring is available from PGRO and NIAB. Uninfected land should not be planted with seed at any level of infection. Where infection has been present in the past, low scores can be planted whilst moderate scores are fine if pulses or oats will not be planted in the same field for four years. High counts (equivalent to 3% in the PGRO test) should not be planted.

Seed treatments

Sowing date
Beans should be sown from mid October to optimise yields (Figure 1.). Earlier sowing may produce plants that are too forward and prone to frost damage whilst yields are reduced as sowing date is delayed.

Figure 2. Sowing date for winter beans cv. Bourdon - mean of three years trials at Nottingham University (1985 to 1988)2 [redrawn from data from Pilbeam et.al., 1990, J. Ag. Sci. (114) 339-52] Click here for a larger image

Plant population
Optimal yields are produced over a wide range of plant populations although higher populations may also increase constraints to yield such as disease and lodging pressure. Figure 2 shows overall response to plant populations from a variety of trials. Optimal yields may be obtained from 12 to 70 plants per m^-2 although at low populations (below 20 plants per m^-2), yields are more variable. Some of the lower yields at low plant density may be due to poor establishment or poor soil conditions, thus a crop sown evenly at a low population is more likely to yield well than a crop established at a low population because of a poor environment. Consistent yields originate from crops established at 20 plants per m^-2 or more. To calculate seed rate go here.

Figure 3. Plant population in winter beans – Results of 13 trials 1981 to 1990. [redrawn from data from Bianco, 1981. Acta Hortic. (111) 200-16; Caballero, 1987. Res.Devt. Agric. (4) 147-50; Ricketts, 1986. BSc dissertation. Nottingham University; Pilbeam et.al., 1990. Ann. Appl. Biol (117) 137-45] Click here for a larger image

Implications of plant population on crop husbandry
High plant populations may not decrease yield but they may reduce profitability through increased constraints and increased need for variable costs. High crop density increases the humidity within the crop canopy, which enhances the environmental requirements for Botrytis spp. and Ascochyta spp. development. Within a season or specific crop, disease pressure increases as plant population increases. The actual population at which disease levels increase will alter for different crops grown in different seasons but the requirement for (mostly preventative) fungicides will increase as plant population increases. An example of this phenomenon is shown in Figure 3.

Figure 4. Effect of plant population on the development of chocolate spot (Botrytis cinerea & Botrytis fabae) in winter beans. [redrawn from data produced by Nottingham University, 1986. Pers.comm.] Click here for a larger image

Lodging pressure also increases with increasing crop density as demonstrated in Figure 4. The specific population at which the crop begins to lodge will differ in different sites and seasons. A similar experiment conducted in Elgin, near Aberdeen with Bourdon demonstrated a linear increase in crop lodging over a plant population of 14 plants per m^-2.

Figure 5. Effect of plant population and row width on the severity of lodging in winter beans [redrawn from data produced by Nottingham University, 1986. Pers.comm] Click here for a larger image

The response of field beans to soil moisture may explain why soil conditions are an important determinant of yield. Research at Nottingham University during the 1980’s showed that crops established in compacted soils develop small, shallow root systems that exploit a smaller volume of soil and take up less water than those grown in a well structured soil. Yields were reduced by up to 15% in experiments over a number of seasons.⁹ Winter beans are suited to soils with good water holding capacity and generally yield better in heavy clays than on light, drought prone land.

Soils and Cultivations

Soils
Winter beans require a good root system, normally rooting to about 1 metre. They are sensitive to poor soil structure, suffering from waterlogging and constriction of root growth. An ideal soil would comprise a well-drained chalky boulder clay.

Cultivations and Crop establishment
Because winter beans are drilled late in the autumn, soil conditions are often less than ideal and soil moisture levels are high. Ploughing in is often the only option with high soil moisture, however it is not the ideal particularly as beans normally follow winter wheat in the rotation, chopped straw ploughed down with the beans is the cause of many problems, forming an anaerobic layer in the soil. The alternative of baling the straw all too often causes soil compaction. Dependent on soil moisture content and soil type, ploughing may be coupled with furrow pressing which will provide a more level surface for spraying and harvesting. Post drilling cultivation can be used to level seedbeds, providing soil structure damage is not caused.

Optimum establishment is achieved by deep drilling, following good ploughing. Most cereal drills are not capable of achieving the optimum of 5 inches (12.5cm). The International S2 springtine coulter drill is the nearest standard drill to achieving the optimum. The best drilling machine, designed by an Essex blacksmith, is a Blench pigtail tine cultivator with a Nodet pneumatic spreader mounted on the frame with a tube attached to each tine. This places the seed at the optimum depth and above any layer of straw. However it is a less weatherproof system than the plough. There is the risk that rain following ploughing, may make the soil too wet to drill.

Tyre choice an usage
As Winter Beans are particularly sensitive to soil structure damage, the correct choice of wheel and tyre equipment, is essential.

Ideally a tyre manufacturer, eg Michelin should be used to advise on choice of tyre equipment for tractors, combines and all trailed equipment. Their representative will visit your farm, with a load cell to determine the weights of the tractors and cultivation, spraying and harvesting equipment on the farm and advise on the optimum tyre choice and working pressures required.

Tyre manufactures also provide valuable training courses for farmers, managers and operators.

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