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MAGIC RECIPES?

Strawberry Fertigation in the UK

John AtwoodSenior Horticultural Consultant

Strawberries in the UK

Raised beds, polythene mulch, trickle line + fertigation

Introduced 20 years agoProduction in soil-less media

e.g Table top, troughs, peat bagsMore widespread in last 10 years

Why Fertigation?

The only method possible for plastic mulched bedsIncreased yield and fruit qualityImproved efficiency of applicationFlexibility to control plant growth response

Strawberry Nutrition

Major ElementsN, P, K, Ca, Mg

MicronutrientsMn, Fe, Cu, Zn, B, Mo

Nitrogen

Most important element in leaves and rootsHighest uptake from start of growth to floweringExcess N causes vegetative growth, softer fruit, more Botrytis

Phosphorus

Important for root development and flower initiationHighest uptake following planting and floweringDuring fruiting P is accumulated in fruit (in seeds) at expense of leaves, petioles and roots

Potassium

Regulates stomatal activityImportant for sugar productionHighest demand during flowering and fruitingFruits accumulate most of the KDoes not necessarily increase fruit firmness

Calcium

Important for development of roots, young leaf and budsImportant for fruit firmnessShortage causes tip burnHigh K, NH4 antagonistic to uptakePeak demand from planting to flowering2 tank system needed to supply

Magnesium

Important for chlorophyll synthesisHigh levels of K are antagonistic Most uptake takes place during vegetative growth and flowering

Iron

Important for the synthesis of chlorophyllHighest uptake during early developmentHigh pH, reduces uptakeWaterlogging, loss of fine root hair, reduces uptakeK, NH4, reduces pH increases uptakeNO3, SO4, PO4, + pH less Fe uptake

Manganese

Catalyst for enzyme systemsEssential for uptake of P and MgHigh pH inhibits uptakeUptake is constant during growth

Boron

Important for root development, vegetative growth and pollen fertilityUptake increases during flowering Narrow band between deficiency and toxicityExcess causes tip burn, leaf scorch, soft fruitHigh P inhibits uptake

Fertigation guidelines

Soil-grown crops

Initial check

Soil indicesWater analysisFertigation equipment limitationsVarietiesProtection

Nutrient off-take from a 20 t/ha crop

N P2O5 K2O 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 Bearers3 - 6 kg/ha/wk for everbearersSources, KNO3, Urea phosphateInitial growth start with higher ratio of N for June bearers Tunnel crops - avoid excess NEverbearers increase N ratio after 1st flush of fruit

Phosphorus

Fertigation useful as PO4 fairly immobileGenerally only apply maintenance levels to avoid blockage problems -1.5 - 2 kg/ha/wkApplication at onset of growth importantUse Urea phosphate if bicarbonate >175 mg/l, otherwise MAPPhosphite formulations now available

Potassium

Generally 4 - 8 kg/ha/wkHigher rates on light soils, low indices, tunnel cropsIncrease K:N ratio from flowering

Typical ProgrammeJune Bearers

Early growth - 1st fruit set - 3 :1 :4 :0.51st fruit set - end harvest - 2 :1 :4 :0.5Post Harvest - 2 :2 :3 :0.5All at 2.5 - 3.5 kg/ha/wk N

Application

Twice per weekTowards end of irrigation cycle leaving 10-15 mins to flush throughApply in 20,000 - 40,000 L/ha = 2 - 4 mm

Feed Recipe ChoicesProprietary

Often supplied in bags of 25 kgOften designed to be used at rate of 1 bag per ha per weekExample - 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 ChoicesStraights

Typically use: Potassium Nitrate (13.5% N, 46% K2O)Urea Phosphate (18% N, 44% P2O5)Ammonium Nitrate (34.5% N) Magnesium Sulphate (16% MgO)+ traces

Feed Recipe ChoicesUsing ADAS Nutriplan

Takes into account water & soil analysisGives an estimate of feed conductivity for checkingClear presentation of recommendations

NutriplanCustomer A GrowerFarm The Fruit Farm Area 1 ha Volume of diluted feed/feed/ha 50000 litresField Elsanta Stock tank 100 litres Stock Use (litres/ha/week) 250Crop 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 P2O5 K2O MgO of weeks N P2O5 K2O 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 recipeCustomer A Grower Crop StrawberryField Name Elsanta Crop Area 1 haFeed A

Nutrient N P2O5 K2O MgORatio 3 1 4 0.5

Volume of stock tank 100 litres

Dilution rate 1 in 200

FEED COMPOSITIONAdd the following fertilisers to your stock tank (all figures in the table are in kg)

Target kg N/ha/week 3 6 9 12 15Potassium nitrate 3.5 7.0 10.5 14.0 17.5Calcium nitrate 0.0 0.0 0.0 0.0 0.0Magnesium nitrate 0.0 0.0 0.0 0.0 0.0Magnesium sulphate 1.0 2.0 3.0 4.0 5.0Ammonium nitrate 1.5 3.0 4.5 6.0 7.5Mono ammonium phosphate 0.0 0.0 0.0 0.0 0.0Mono potassium phosphate 0.0 0.0 0.0 0.0 0.0Urea phosphate 1.0 2.0 3.0 4.0 5.0

Conductivity of feed @ 20 °C (µS) 590 1180Conductivity of feed @ 25 °C (µS) 650 1298

TRACE ELEMENTS Iron EDTA 154 gManganese sulphate 31 gCopper sulphate 4 gZinc sulphate 17 gSolubor 19 gDo not vary these weights

More Later…..