Grassland P & K Advice Mark Plunkett Johnstown Castle, Wexford Mark Plunkett, Teagasc Grassland P & K Advice Mark Plunkett Johnstown Castle, Wexford

Soil P – Grassland Farms Mark Plunkett, Teagasc Soil P – Grassland Farms Soil P for Grassland Soils 64% Index 1 & 2 Target Index 3 Soil P fertility decreasing over time 64% of soils P Index 1 and 2 Aim for P Index 3 Soil P fertility continues to decrease

Soil K for Grassland Soils Mark Plunkett, Teagasc Soil K - Grassland Soil K for Grassland Soils 61% < Index 1 & 2 Target Index 3 Soil K fertility decreasing over time 57% of soils K Index 1 and 2 Aim for P Index 3 Soil Kfertility continues to decrease

Soil P & K Trends - Grassland Farms Mark Plunkett, Teagasc Soil P & K Trends - Grassland Farms P and K Trends over time 42,572 Soils

Mark Plunkett, Teagasc 91% of soils sub optimal for pH, P & K

Step 1 - Reliable Soil Results Mark Plunkett, Teagasc Step 1 - Reliable Soil Results “Soil results are only as good as the sample on which it is based on” “Greatest potential for error is in field sampling” Take a representative soil sample Establish an accurate estimate of the soils nutrient status 10cm sampling depth represents a volume of approx. 1,500 tonnes/ha of soil Sample every 4 to 5ha Take soil samples as per soil sample guidelines to ensure reliable results = 6,000 to 7,500t Soil

Peaty Soils & P Application Peats type soils have no minerals such as and / silt / clay Very little Iron / Aluminium Therefore low ability to retain P Increased risk of P loss to water Apply maintenance P rates Morgan’s P over estimates soil P availability Therefore poor indicator of peat soil P status

Soil Sampling Changes Check map & determine if peaty or not Peat Soils Certification & Soil Organic Map Check map & determine if peaty or not Advisor signs off on peat or non peat Where advisor signs off No Analysis required If unsure test for SOM >20% OM or Advisor signs off on peat only apply P Index 3 rates

Soil Organic Matter Layer Map

Role & Function of P Rooting & Tillering Mark Plunkett, Teagasc Role & Function of P Rooting & Tillering Kick starts spring grass growth Extra 1.5t DM/ha Animal health 0.35% P in Grass Meat & Milk Function and role of P in grass production

Irish Soils & P Fixation Mark Plunkett, Teagasc Irish Soils & P Fixation Effect of soil pH on soil P availability – Aim for pH 6.3 to 6.5 to maximise soil P availability

Irish Soils & P Fixation Mark Plunkett, Teagasc Irish Soils & P Fixation Irish soils are naturally acidic High levels of Aluminium & Iron Fix P applied to soils Response to applied P very poor Lime increases soil pH & unlocks soil P Building Soil P will take time depending on the soil type and level of P fixation Applying P to acidic soils results in P fixed by Al & Fe

Acidic Soils Fix P – Mineral Soils Mark Plunkett, Teagasc Acidic Soils Fix P – Mineral Soils P Fertiliser “Acidic soils competes for freshly applied P & its is Fixed by Al & Fe” “Manure P more available in acidic soils” P Al Explains soil P fixation Fe P Acidic Soil

Unlocking Soil P with Lime! Mark Plunkett, Teagasc Unlocking Soil P with Lime! Average change in soil test P (Morgan’s) across 16 soils (av. pH 5.5) treated with P (100 kg/ha of P), Lime (5 t/ha of lime), and P + Lime and incubated over 12 months in controlled conditions Lime will increase soil P availability and freshly applied P is more available

Role & Function of K N & P Efficiency Prevents Lodging Mark Plunkett, Teagasc Role & Function of K N & P Efficiency Prevents Lodging Silage Production Extra 3t/ha 2 cut silage removes 250kg/ha Slurry excellent K Potassium vital role to play in N efficiency and water regulation in the plant K vital in grass silage production. Ideally recycle slurry back to silage fields

Irish Soils & K Good levels of K 5% of total K is available Mark Plunkett, Teagasc Irish Soils & K Good levels of K 5% of total K is available K found in the clay component Soil test very reliable Easy to improve soil K compared to P Soil type (light v heavy) Some K fixing soils (for example Athy) Peat soils and K?? Irish soils have good levels of soil K. Soil K will respond / change faster than soil P

Soil Test Results

Soil P & K Index System Basis to Index System Mark Plunkett, Teagasc Soil P & K Index System Basis to Index System Index 4 – Very Fertile Soils Index 3 – Soil Feeding the crop & Replacing off-takes Index 1 & 2 – Building soil fertility Soil P & K Index system Basis to Index system

Why Build Soil Fertility? Mark Plunkett, Teagasc Why Build Soil Fertility? Index 3 Low response to fertilizer Index 4 Soil supply sufficient to meet demands Large variation between soil types! Index 1 & 2 Yield response to increased soil P levels ~ 1.5 t/ha Cost of not knowing soil is in Index 1 is approximately 1.5 t/ha of grass DM per year Large variation around this average estimate (0-5 t/ha) Average of response curves from 8 sites over 4 years. (32 repeated experiments). K – Similar response in silage (1-3 t/ha/yr)

How much P and K to replace offtake? Mark Plunkett, Teagasc How much P and K to replace offtake? P (kg) K (kg) Milk (1,000 litres) 0.9 - 1 1 - 1.5 Meat (Live wt.) (100 kg) 1 0.5 - 1 Silage (1 ton DM) 3 - 4 25 Grain (1 ton grain + straw) 3.8 10-15 P and K offtakes for milk / meat / silage / grain Lalor – ASA Conference, Killeshin Hotel, Portlaoise 20 Mar 2014

How much P & K Removed? Stocking Rate / ha Product P (kg) K (kg) Mark Plunkett, Teagasc How much P & K Removed? Stocking Rate / ha Product P (kg) K (kg) 10,000L Milk 10 15 15,000L Milk 23 1,200 kg Meat 12 X 24 1,100kg 11 P & K Off takes by stocking rates Lalor – ASA Conference, Killeshin Hotel, Portlaoise 20 Mar 2014

P & K advice – replacing offtake Mark Plunkett, Teagasc P & K advice – replacing offtake Stocking Rate (LU/ha) 1.5-2.0 2.0-2.5 2.5-3.0 > 3.0 Dairy P – K advice kg/ha 14 – 30 19 – 35 23 – 40 27 – 45 units/acre 11 – 24 15 – 28 18 – 32 22 – 36 Stocking Rate (LU/ha) 1.0-1.5 1.5-2.0 2.0-2.5 2.5-3.0 Beef/Sheep P – K advice kg/ha 7 – 10 10 – 15 13 – 20 16 – 25 units/acre 6 – 8 8 – 12 10 – 16 13 - 20 P and K advice for dairy & drystock P and K rates for drystock are low

P & K Advice – Off takes Grass Silage Mark Plunkett, Teagasc P & K Advice – Off takes Grass Silage Cut 1st 2nd P – K advice kg/ha 20 – 125 12 – 75 units/acre 16 – 100 10 – 60 P and K advice for 1st & 2nd cut silage

P & K – Build Up Rates Build-up Index 1 Index 2 P – K advice kg/ha + Mark Plunkett, Teagasc P & K – Build Up Rates Build-up Index 1 Index 2 P – K advice kg/ha + 50 – 60 30 – 30 units/acre 40 – 48 24 – 24 P and K build up rates P increased by 30kgP/ha at Index 1 P increased by 20kgP/ha at Index 2

How long does it take to change Index ? Mark Plunkett, Teagasc How long does it take to change Index ? P Generally takes time to increase/decrease (5 to 10 years) Lighter soils tend to move quicker Organic matter content % Clay Advice 1st Correct Soil pH Apply fertilizer as per fertiliser plan for a number of years Re-test every 3-5 years to monitor changes over time K Will change faster than P Index 1 & 2 Apply off takes + build-up until next soil test Index 4 Omit K for one year, then revert to Index 3 advice (off takes) On av. 50kgP/ha req. for 1mg/L P On av. 1kgK/ha req. for 1mg/L K Changing soil P takes time while soil K will change faster

New Fertiliser P Allowances Mark Plunkett, Teagasc New Fertiliser P Allowances Grassland Stocking Rate (kg/ha) P Index 1 2 3 4 131 - 170 63 43 13 171 - 210 66 46 16 211 - 250 >250 69 49 19 50kg P/ha @ Index 1 30kg P/ha @ Index 2 1. Adjust for Conc. Feed (5kg/ton) 2. Slurry Removed from calculations New P allowances Complete Farm Fertiliser Plan to Determine P Allowances

Mark Plunkett, Teagasc P & K advice – In Summary Take good soil samples for reliable P & K results Correct soil pH before building soil P Determine P & K advice Takes time to increase soil P while K will increase quicker New Nitrates allow extra P for build up Summary