Description

LIME APPLICATION RECOMMENDATIONS

(tonnes/hectare*)

multiply by 0.4047 to obtain tonnes per acre

NOTES

• Recommendations based on soil depths of 200mm/8in (arable) and 150mm /6in (grassland). Greater depths of soil will require more lime.
• Maximum surface application for grass is 7 tonne/ha (3 tonne/acre). Minimum application rate: 2 tonne/ha (1 tonne/acre). Where application rates of over 10 tonnes/ha (4 tonnes/acre) are necessary on arable land the ALA recommends that lime should be applied as two dressings (first dressing ploughed in).
• The application rates shown are based on material having a neutralising value of 54 and fineness of 40% passing 150 microns. When using other materials permitted under the Fertiliser Regulations the dressing should be adjusted accordingly. Thus coarser materials and those having a lower neutralising value will also require a heavier dressing.

SAMPLING FOR ASSESSMENT OF LIME REQUIREMENTS

Soil samples should be taken methodically from a number of places in the field and tested individually since acidity frequently occurs in patches in the field. Test results should be plotted on a field map so that any lime required may be applied in the right place and at the correct and most economic rate. Although poor and patchy crop performance and the presence of acid loving weed species are rough indications of lime deficiency, the acid reaction to indicator solution or pH meter is the only reliable method of assessing lime requirements.

Crop requirements

pH Management + Natural Lime = Successful Crops

The replacement of calcium lost from the soil by leaching and crop uptake is essential to maximise production and profits from cereal crops.

The growth of cereals of high protein content depends on stability of pH during the growing cycle; barley is an example where sensitivity to soil pH is particularly apparent. Sugar beet also takes up nutrients most effectively in soils with a pH 6.5-7.0. Increasing acidity results in stunted plants and fangy roots.

The crop requirements diagram provides a guide to the optimum pH levels for some important crops. If soil pH is lower than the bottom of the indicated range, then crop yields will begin to suffer severely due to the crops’ inability to tolerate that level of acidity. Those crops which are tolerant to acidity would be more profitable at higher pH values. At a pH of 4.9 one is not getting as good a response from the fertilisers applied to maximise the potato crop as at the optimum pH. Lime also aids soil fertility in grassland and ensures that added fertilisers are utilised to maximum effectiveness and helps to increase crop yield either as hay, silage, or grazing. It is particularly important to adjust soil pH well in advance for sensitive crops such as oilseed rape, sugar beet, barley and peas. Spreading should be even, accurate, and cause little disruption to the soil structure.

Liming for profit

Natural lime the best long term investment

The results from this liming trial (below) showed us that four years after the initial lime treatments, further lime dressings were needed on plots receiving the 11 t/ha (4.5t/acre) treatment. This is typical of the normal liming interval for light-textured soils in low rainfall areas.

The effects of the lime treatments on the growth and yield of sugar beet, spring barley and spring wheat were monitored for three years. Acidity symptoms were clearly visible in crops on the control plots which received no lime but there was no root or leaf damage on any of the limed plots. Crop growth was, however, more vigorous on the plots receiving the highest rate of lime, showing low soil pH can have an adverse effect on growth, even when no acidity symptoms are visible.

Crop growth was also closely related to soil pH value and consistent yield increases came with increasing soil pH in all four years of the experiment. The yield responses resulting from an increase of 1 pH unit were 9.2t/ha (3.7t/acre) of sugar beet in the first year; 0.7t/ha (0.3t/acre) of spring barley in second year; 3.6t/ha (1.5t/acre) of sugar beet in third year; and 0.2t/ha (0.8t/acre) of spring wheat in fourth year.

The economic benefit from liming was assessed by calculating the cumulative value of the crop yield increases and comparing that with the cost of the liming. Returns were adjusted to first year values.

The benefits of liming vary but the greatest returns will be achieved by maintaining the soil pH in a narrow range within about 0.2 units of the optimum pH value.

When the cost of lime is related to the long-term benefits, it is one of the best investments you can make.

pH 5.5 pH 6.7 The benefits of lime applications to arable crops were investigated by ADAS in an experiment sponsored by the Agricultural Lime Association. The trial site near Wetherby, North Yorkshire was on a sandy loam soil and had an initial pH value of 5.1 Lime requirement was 11t/ha (4.5t/acre). The experiment assessed the effect of 0, 5.5, 11 and 22 t/ha (0, 2.2, 4.5, and 9t/acre) of screened limestone applied during first winter. Soil analysis results confirmed progressive increases in soil pH values with increasing rates of lime application. The highest soil pH values were achieved in the first or second year after lime application. After that the pH level began to decline. At no stage did the recommended dressing of 11 t/ha (4.5t/acre) achieve the target pH value of 6.7. The results confirmed the reduced effectiveness of screened limestone compared with ground limestone.

LIME IS A FERTILISER

The addition of lime helps to release soil nutrients. Fertilisers and manure cannot be fully effective if the land is short of lime. In addition, water that leaches from acid soils may contain undesirable materials which can adversely effect the quality of surface and groundwaters.

Heightened environmental controls and regulations on the disposal of sewage and other industrial wastes to landfill or sea outfalls have led to an annually increasing volume of application to agricultural land. These products do bring beneficial residual fertiliser and organic matter to the soil. However, problems do arise as these wastes also contain a number of metallic and other inorganic Potentially Toxic Elements (PTEs). With repeated applications these contaminants accumulate in the soil and can remain indefinitely, causing restrictions on plant growth, increased uptake of metals by animals and man via the food chain and reductions in soil microbial activity. Heavy metals become more available in acid soils and adverse effects will then increase. When sludge or waste is applied there will be a need to maintain alkaline pH values for an indefinite period thereby inhibiting the release of heavy metals, whilst gaining the manurial values of the material.

Agricultural lime is used to correct acidity and provide the right conditions in which plants and aquatic life can develop. It has a major influence on:

• Plant development
• Efficient use of fertilisers
• Bacterial activity in the soil
• Animal health
• Water quality in rivers and streams
• Development of woodland areas
• Soil structure
• Efficient use of herbicides