PDA News
The PDA publishes both technical News items and shorter Blog items. PDA News provides the latest up to date information on macronutrients and their use, while blog items are shorter and timelier.
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Optimising potash use on cut grassland
Grass cut regularly, as silage, haylage or hay, removes very large amounts of potassium (K). Unless this is replaced, soil K concentrations will fall. In recent years there is evidence of an overall increase in the number of grassland soils below target index (2-), as well as a decline in the use of potash fertiliser. This situation is not sustainable and grass yields will fall unless corrected.
April 2016
How we apply potash
Having worked out the rate of nutrient potash required for a crop or grass, and considered the timing of the applications, we now have to select a suitable fertiliser product or other source, such as organic manures, to apply to the soil or crop. Then we have to apply it effectively to suit the crop being grown.
January 2016
Planning potash applications
As growers and advisers we need to know how much potash we should apply to ensure crops thrive in terms of yield and quality. Previous articles have described the way soils hold potash and how the plants use it. This article takes us on to the reality of deciding how much, and when to apply […]
August 2015
The role of potash in plants
Ian Matts, Company Agronomist, Yara UK Potassium is one of the major nutrients required by all crops and is present in large quantities in the plant in the form of the cation K+. It plays a major role in achieving the maximum economic yield, as part of a balanced approach to crop nutrition, as well […]
May 2015
Soil texture and pH effects on potash and phosphorus availability
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 […]
January 2015
High Yields – are we keeping up with Potash offtakes?
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 […]
September 2014
Measuring potassium in soil and crop
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’, […]
June 2014
Nutrient recycling by grazing cattle
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 […]
October 2013
Fertiliser base dressings and timing
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 […]
July 2013
What are the effects of potash deficiency?
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 […]
March 2013
Calculator for estimating nutrients needed to correct soil deficiency
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 […]
October 2012
Standard recommendations cannot make a poor soil good overnight
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 […]
July 2012