Weather halting spring crop work
Mark Plunkett, Teagasc Soil & Plant Nutrition Specialist, tells us that over the last number of weeks, field operations in tillage fields has been reduced due to poor weather and soil conditions.
Many winter crops still await their main N application which should be a priority once field conditions improve. In addition, early sown spring crops are at or close to requiring their main N split.
Seedbed fertiliser
For spring crops not sown yet ensure a suitable compound fertiliser such as 10-10-20 / 12-8-20 / 13-6-20 etc… for example on very low to low (Index 1 or 2) fertility soils, 10-10-20 / 12-8-20 would be the products of choice. While on medium fertility soils, (Index 3) 13-6-20 is a well balance fertiliser product for spring barley. Aim to apply ~ 370kg/ha (3 bags/ac) at sowing time and where possible combine drill especially on low index soils to increase fertiliser P efficiency and supply.
Applying sufficient phosphorus (P) is essential for rapid root and tiller development and is critical in spring barley in the first 3 to 6 weeks of establishment. Trial work carried out in spring barley clearly shows the benefits of combining P especially on low P Index sites (1 & 2). While potassium (K) is very important for N efficiency, grain yield development and straw strength and quality. A number of trials carried out in Arklow, Co. Wicklow in 2015/2016/2017 clearly showed the importance of K in grain yield formation and N efficiency. These trials highlighted the role of K in reducing the effects of straw brackling (breakdown) prior to harvest. Potassium untreated plots were more tolerant to foliar diseases such as powdery mildew infection.
Key an eye on fields that are being ploughed out of long-term grass silage / hays fields as these fields maybe have very low soil P & K levels, resulting in crop P and K deficiencies. It will be very difficult to correct especially a P deficiency, as the P is needed in the seedbed zone and close to the rapidly developing seed / roots. Therefore, ensure sufficient available fertiliser P and K are applied at sowing time.
Nitrogen & Sulphur (S) applications to spring barley
For spring crops still be sown aim to supply ~ 30% of the crops N requirements in the seedbed and apply remaining N+S once tramlines are visible. For early sown malting barley crops aim to top-dress with N + S once soil conditions are suitable. For feeding barley, crops aim to apply remaining crop N + S requirements at mid-tillering in a single application or alternatively split 70:30 and complete N applications by stem extension (GS 31/32). Aim to apply 15kg S/ha.
Where organic fertilisers have been applied, adjust final N applications to take account of N supplied. For example an application of 33mᶾ/ha of cattle slurry by LESS and ploughed in rapidly can supply ~ 33kg N/ha offering a saving in chemical N of ~€65/ha at today’s fertiliser N prices.
Trace Elements (Mn, Cu & Zn)
Soil test results are a very good indication of the soil supply of both copper (Cu) and zinc (Zn). The soil test is not as reliable for manganese. Manganese (Mn) deficiency tends to be most prevalent on sandy or lights soils, recently limed or high pH soils, poorly consolidated seedbeds or under dry and cold weather conditions. Ensure seedbeds are well consolidated after sowing where possible for example on fields ploughed out of grass leys ideally flat roll after sowing to improve seed to soil contact to reduce the incidence of Mn and other nutrient deficiencies. Where trace element deficiencies are anticipated based on soil test results inclusion of trace elements in base fertilisers at sowing is a very good strategy on soils with recurring trace element deficiencies. Alternatively, foliar treat crops once sufficient leaf is present for uptake e.g. 2 to 4 leaf stage.