MAGIC RECIPES? Strawberry Fertigation in the UK John Atwood Senior Horticultural Consultant www.adas.co.uk
Strawberries in the UK Raised beds, polythene mulch, trickle line + fertigation Introduced 20 years ago Production in soil-less media e.g Table top, troughs, peat bags More widespread in last 10 years
Why Fertigation? The only method possible for plastic mulched beds Increased yield and fruit quality Improved efficiency of application Flexibility to control plant growth response
Strawberry Nutrition Major Elements N, P, K, Ca, Mg Micronutrients Mn, Fe, Cu, Zn, B, Mo
Nitrogen Most important element in leaves and roots Highest uptake from start of growth to flowering Excess N causes vegetative growth, softer fruit, more Botrytis
Phosphorus Important for root development and flower initiation Highest uptake following planting and flowering During fruiting P is accumulated in fruit (in seeds) at expense of leaves, petioles and roots
Potassium Regulates stomatal activity Important for sugar production Highest demand during flowering and fruiting Fruits accumulate most of the K Does not necessarily increase fruit firmness
Calcium Important for development of roots, young leaf and buds Important for fruit firmness Shortage causes tip burn High K, NH 4 antagonistic to uptake Peak demand from planting to flowering 2 tank system needed to supply
Magnesium Important for chlorophyll synthesis High levels of K are antagonistic Most uptake takes place during vegetative growth and flowering
Iron Important for the synthesis of chlorophyll Highest uptake during early development High ph, reduces uptake Waterlogging, loss of fine root hair, reduces uptake K, NH 4, reduces ph increases uptake NO 3, SO 4, PO 4, + ph less Fe uptake
Manganese Catalyst for enzyme systems Essential for uptake of P and Mg High ph inhibits uptake Uptake is constant during growth
Boron Important for root development, vegetative growth and pollen fertility Uptake increases during flowering Narrow band between deficiency and toxicity Excess causes tip burn, leaf scorch, soft fruit High P inhibits uptake
Fertigation guidelines Soil-grown crops
Initial check Soil indices Water analysis Fertigation equipment limitations Varieties Protection
Nutrient off-take from a 20 t/ha crop N P 2 O 5 K 2 O Mg Fruit 30 17 49 3 Leaf & Crown 29 12 27 5 Total 59 29 76 8
Nitrogen 2.5-4 kg/ha/wk for June Bearers 3-6 kg/ha/wk for everbearers Sources, KNO 3, Urea phosphate Initial growth start with higher ratio of N for June bearers Tunnel crops - avoid excess N Everbearers increase N ratio after 1st flush of fruit
Phosphorus Fertigation useful as PO 4 fairly immobile Generally only apply maintenance levels to avoid blockage problems - 1.5-2 kg/ha/wk Application at onset of growth important Use Urea phosphate if bicarbonate >175 mg/l, otherwise MAP Phosphite formulations now available
Potassium Generally 4-8 kg/ha/wk Higher rates on light soils, low indices, tunnel crops Increase K:N ratio from flowering
Typical Programme June Bearers Early growth - 1st fruit set - 3 :1 :4 :0.5 1st fruit set - end harvest - 2 :1 :4 :0.5 Post Harvest - 2 :2 :3 :0.5 All at 2.5-3.5 kg/ha/wk N
Application Twice per week Towards end of irrigation cycle leaving 10-15 mins to flush through Apply in 20,000-40,000 L/ha = 2-4 mm
Feed Recipe Choices Proprietary Often supplied in bags of 25 kg Often designed to be used at rate of 1 bag per ha per week Example - Kemira 13:4:42 at 1 bag per ha per week Divide by 4 to give rate of N per ha per wk = 3.25 kg N per ha per wk.
Feed Recipe Choices Straights Typically use: Potassium Nitrate (13.5% N, 46% K 2 O) Urea Phosphate (18% N, 44% P 2 O 5 ) Ammonium Nitrate (34.5% N) Magnesium Sulphate (16% MgO) + traces
Feed Recipe Choices Using ADAS Nutriplan Takes into account water & soil analysis Gives an estimate of feed conductivity for checking Clear presentation of recommendations
Nutriplan Customer A Grower Farm The Fruit Farm Area 1ha Volume of diluted feed/feed/ha 50000 litres Field Elsanta Stock tank 100 litres Stock Use (litres/ha/week) 250 Crop Strawberry Dilution 1 in 200 Stock Use (litres/crop area/week) 250 Growth Stage Period N rate Nutrient Ratio Feed Number Nutrients applied (kg/ha/week) N P 2 O 5 K 2 O MgO of weeks N P 2 O 5 K 2 O MgO (kg/ha) Early growth - Flowering April - Early May 3 3 1 4 0.5 A 4 12 4 16 2 Fruiting Mid May - End July 2.5 2 1 4 0.5 B 6 15 8 30 4 Post Fruiting August - Early Sept 3 2 2 3 0.5 C 6 18 18 27 5 TOTAL 45 30 73 10 Note Fruiting = from1st green fruit set
Nutriplan recipe Customer A Grower Crop Strawberry Field Name Elsanta Crop Area 1 ha Feed A Nutrient N P 2 O 5 K 2 O MgO Ratio 3 1 4 0.5 Volume of stock tank 100 litres Dilution rate 1 in 200 FEED COMPOSITION Add the following fertilisers to your stock tank (all figures in the table are in kg) Target kg N/ha/week 3 6 9 12 15 Potassium nitrate 3.5 7.0 10.5 14.0 17.5 Calcium nitrate 0.0 0.0 0.0 0.0 0.0 Magnesium nitrate 0.0 0.0 0.0 0.0 0.0 Magnesium sulphate 1.0 2.0 3.0 4.0 5.0 Ammonium nitrate 1.5 3.0 4.5 6.0 7.5 Mono ammonium phosphate 0.0 0.0 0.0 0.0 0.0 Mono potassium phosphate 0.0 0.0 0.0 0.0 0.0 Urea phosphate 1.0 2.0 3.0 4.0 5.0 Conductivity of feed @ 20 C (µs) 590 1180 Conductivity of feed @ 25 C (µs) 650 1298 TRACE ELEMENTS Iron EDTA Manganese sulphate Copper sulphate Zinc sulphate Solubor Do not vary these weights 154 g 31 g 4 g 17 g 19 g
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