Dr Paul Hargreaves, SRUC, Crichton, Dumfries. The application, use, efficiency and loss of nutrients including K and P can vary with soil type. Soil type is generally determined by the texture of the soil, which is a measure of the proportions of the following three particles: sand, classified as having a particle size between 0.05mm […]

The Fertiliser Manual (RB209) gives recommendations for phosphate and potash applications for arable crops and grass based on that needed to replace the amount that will be removed from the soil by crop offtake at harvest. In addition, where soil analysis is below target, it adds a small amount to build up the soil reserves […]

At a time when a crop is looking at its best, as is usually the case at this time of year, there may be little incentive to think about deficiencies. However crops can appear to be perfectly well fed yet still be deficient in potash. This ‘invisible’ deficiency is often referred to as ‘hidden hunger’, […]

Grazing livestock return most of the nutrients they consume to the soil. This sounds good but a glance at any grazed pasture will show that the recycling is not done very well. There are many patches where dung or urine has been deposited but most of the field is unaffected. In paddock grazing systems where […]

Nitrogen fertilisation for good yields can be effectively managed at SNS Index 0, because nitrogen fertiliser is applied each year to make good the supply from the soil and to meet the needs of the crop. But we cannot do this with potash (nor with phosphate) on P or K Index 0 soils because it […]

We write ‘effects of potash deficiency’ rather than ‘symptoms of deficiency’, because so many of the negative effects of a shortage of available potash to crops are not clearly apparent, whereas ‘symptoms’ implies some visible effect. Of course severe deficiency has visible symptoms (Figure 1), but there can be many expensive negative impacts on the […]

In the previous Newsletter it was noted that in many cases it could take between 10 and 20 years to change the nutrient status of a soil from Index 1 to 2 if only the additional 30 kg/ha as suggested in the Fertiliser Manual (RB209) is added to the crop offtake when making a phosphate […]

A crop receiving the rate of potash (or phosphate) recommended in the Fertiliser Manual (RB209) for a soil at Index 0 or 1 is still very unlikely to perform as well as it could on an Index 2 soil. The standard recommendation at phosphorus (P) or potassium (K) Index 0 or 1 is in two […]

In the spring there is understandably much talk of nitrogen applications, growth regulators and how well crops have come through the winter. It is seldom accompanied by discussion of the importance of potash on the efficiency of nitrogen utilisation, on the ability of cereal crops to resist going down, or on the resistance of the […]

In a recent Newsletter the pattern of uptake of potassium and some other nutrients during the growing season was shown. The same French data-set also analysed the crops for the patterns of nitrogen (N) and sulphur (S) uptakes. The majority of the N and S in crops (other than the Brassicae, such as oilseed rape, […]

Fertiliser recommendations for potash (K2O) are usually based on removal or offtake of K2O at harvest. Some detailed results of measurements on K2O uptake during crop growth show that greater care is needed to ensure potash supply meets crop requirement. Difference between uptake and offtake The amount of a nutrient needed for full growth of […]

Yields of first cut grass have been lower than average in many parts of the UK. Pockets of the south west and N Ireland aside, yields down by as much as 30% have been reported from Wales, Scotland and the midlands, north west and north east of England. Some grassland farmers may have delayed cutting […]