Nutrient Management Planning for Horticulture

The Fruit Farm, Llanvihangel Crucorney

Llanvihangel Crucorney Fruit Farm is a 7.6 hectare mixed horticulture farm which is starting to be managed to organic standards (not certified organic). Currently the apples are not being managed organically. The main enterprise is the orchard with 3.2 ha of dessert apples. Around 0.6 ha of pears are also grown. Soft fruit including strawberries, raspberries, tayberries, black currants, red currants, gooseberries and blackberries are also grown. Recently a 1 ha vegetable patch has been developed, growing a variety of crops including pumpkin, broccoli, beans, brassicas and salads.

Soil samples were taken strategically to cover all the growing areas and the range of crops grown, numbering 20 samples in total.

 

Soil analysis results

Soil pH

Optimum soil pH is vital to maximise the uptake of nutrients. The optimum pH is 6.5 for horticultural crops.

• All of the 20 samples (from orchard, soft fruit & vegetables) were below the recommended target pH of 6.5 and require liming as a priority
• Blueberries tolerate acid conditions (pH 4.5-5.5); if this crop is to be grown in future, they could be planted in the plots with the lowest pH
• Lime can only be applied to orchards and soft fruit by surface broadcast so top dress the top soil around the root zone with the equivalent of 5 t/ha ground limestone; rotovating to incorporate lime may be possible but there is a risk of damage to roots.
• Plough the equivalent of 5 t/ha ground limestone into the vegetable patch and top dress with a further 5 t/ha
• Retest all areas in 2 years’ time to assess improvement

Soil Phosphorus (P)

Soil phosphorus is an essential element classified as a macronutrient because of the relatively large amounts of P required by plants. Phosphorus is one of the three nutrients generally added to soils in fertilizers. P is important for:

• transfer of energy in reactions within plant cells
• stimulates early plant growth and accelerates maturity

The optimum phosphorus index for crop yield is 2 (16-25 mg/l) for fruit and 3 (26-45 mg/l) for vegetables.

• 10 (50%) of the 20 samples were at target P Index of 2-3
• 3 (15%) of the 20 samples were below target P index, with 2 plots particularly deficient at P Index 07 (35%) of the 20 samples were at P index 4 or higher, including the 1 sample at Index 7; no inputs of Phosphate (fertilisers or organic manures) should be applied to these fields until P Index has fallen to Index 3
• Exceptions include crops such as Leafy Salads, Asparagus, Self-Blanching Celery, Hops where applications of phosphate may be appropriate at Index 4

Soil potassium (K)

Potassium (K) is an essential nutrient for plant growth. Because large amounts are absorbed from the root zone in the production of most agronomic crops, it is classified as a macronutrient. The exact function of K in plant growth has not been clearly defined. Potassium is associated with movement of water, nutrients, and carbohydrates in plant tissue. The optimum soil potassium index for crop yield and the utilisation of other nutrients is 2 + (181-240 mg/l).

 

• 20% of the 20 samples were at target K Index of 2+ with 45% at Index 3 (high but appropriate)
• 35% of the samples were slightly low in Soil Potassium (Index 2-)
• Under an organic system, a derogation from the certification body would be required prior to buying in approved forms of potash e.g. sylvinite; a K index of 0 is normally required to demonstrate the need for the derogation

Soil magnesium (Mg)

Magnesium is the central core of the chlorophyll molecule in plant tissue. Thus, if Mg is deficient, the shortage of chlorophyll results in poor and stunted plant growth.

Magnesium also helps to activate specific enzyme systems. Enzymes are complex substances that build, modify, or break down compounds as part of a plant's normal metabolism. The optimum soil magnesium index for crop yield and the utilisation of other nutrients is 2 (51-100 mg/l).

• All (100%) of the 20 samples were at target Mg Index of 2 or above.
• 15% of the samples were slightly high in Soil magnesium (Mg Index 4).
• The K:Mg ratio is particularly important in fruit with a ratio in excess of 3:1 likely to induce magnesium deficiency; several plots were found to have a K:Mg ratio in excess of 3:1

Nutrient application recommendations

Apples – Yield <40t/ha (16 t/ac) (Apples Top, Mid)

Soil Nutrient	Soil Index	Crop Requirement  Kg/ha (Units/acre)	Contribution  from Manure	Balance to be Supplied
Nitrogen	2	30 (24)	0	30 (24)
Phosphate	0	80 (64)	0	80 (64)
Potash	2-	80 (64)	0	80 (64)

 

 

• Applying an organic approved phosphate fertiliser such as ‘GAFSA’ should be considered. The limestone will need to be surface applied within the root zone as there are no options to apply lime to the subsoil; the equivalent of 1,000kg/ha would equate to 1kg per 10 m2
• Lime should not be applied within 6 months of using GAFSA
• Conventionally applying the equivalent of 125 kg/ha TSP (46%) would be recommended
• Soil K index should not be built up above 2 because excessively large potash applications can adversely affect storage quality
• Currently the K:Mg ratio does not exceed 3:1

Pears

Soil Nutrient	Soil Index	Crop Requirement  Kg/ha (Units/acre)	Contribution  from Manure	Balance to be Supplied
Nitrogen	2	90 (72)	0	90 (72)
Phosphate	2	20 (16)	0	20 (16)
Potash	2+	80 (64)	0	80 (64)

 

Pears require an additional 70kg/ha potash. Application of an ‘approved organic’ manure which provide N, P and K would be appropriate in this crop. An organic chicken manure pellet is used on the farm (1.5:2:2). Applying at an equivalent rate of 1,000kg/ha would supply 15 kg nitrogen, 20 kg phosphate and 20 kg potash.

 

Raspberries

Soil Nutrient	Soil Index	Crop Requirement  Kg/ha (units/acre)	Contribution  from Manure	Balance to be Supplied
Nitrogen	Medium	70 (56)	0	70 (56)
Phosphate	5-7	0	0	0
Potash	3	60 (48)	0	60 (48)
Magnesium	2	50 (40)	0	50 (40)

 

• Lime is the priority for the raspberries. Given the requirement for magnesium at Index 2, the use of magnesian limestone would be recommended for the plots. The limestone will need to be surface applied within the root zone as there are no options to apply lime to the subsoil. The equivalent of 5 t/ha would equate to 0.5kg per 1 m2. This should be repeated twice yearly with soil retested in year 2 to assess change in pH
• Currently the K:Mg ratio exceeds 3:1 and this could induce magnesium deficiency; no inputs of K are therefore recommended until the K:Mg ratio falls below 3:1
• If plots are to be managed to organic standards and organic manures cannot be used due to the high P indices, there are few options to apply N

Broad Beans

Soil Nutrient	Soil Index	Crop Requirement  Kg/ha (Units/acre)	Contribution  from Manure	Balance to be Supplied
Nitrogen	Low	0	0	0
Phosphate	2	100 (80)	0	100 (80)
Potash	2-	100 (80)	0	100 (80)

 

• There is no requirement for Nitrogen with leguminous crops
• Applying an organic approved phosphate fertiliser such as ‘GAFSA’ should be considered; the equivalent of 1,000kg/ha would equate to 1kg per 10 m2
• Applying 500kg/ha sylvinite would provide 80 kg/ha potash

Onions and leeks

Soil Nutrient	Soil Index	Crop Requirement  Kg/ha (Units/acre)	Contribution  from Manure	Balance to be Supplied
Nitrogen	Low	130-190 (104-152)	0	130-190 (104-152)
Phosphate	2	100 (80)	0	100 (80)
Potash	2+	125 (100)	0	125 (100)

 

• Organic chicken pellets (equivalent of 1,000kg/ha) could be ploughed down to the root zone with additional pellets (equivalent of 500kg/ha) to the top soil
• Alternatively applying an organic approved phosphate fertiliser such as ‘GAFSA’ should be considered; the equivalent of 1,000kg/ha would equate to 1kg per 10 m2
• Applying 500kg/ha sylvinite would provide 80 kg/ha potash

 

CONCLUSIONS

• Regular soil testing should be carried out to allow for appropriate use of fertiliser, lime and organic manures
• Results show that growers have the potential to improve crop production where soil results indicate deficiencies or incorrect nutrient ratios
• Leaf or fruit analysis could also be considered as a means of diagnosing nutritional disorders and storage potential
• Results will allow fertilisers to be targeted to the areas that need them the most
• Organic approved sources of phosphate and potash should be sourced to allow management of the plots in line with organic standards

The Nutrient Management Guide RB209 (updated May 2017) is an essential resource for growers. It can be downloaded free from:

https://ahdb.org.uk/projects/RB209.aspx

Nutrient Management Planning for growers is available through the Farming Connect programme Advisory Service and is eligible for 80% funding.