By Bill Petrie

Getting plants off to a good start and growing well is important, given that the first six weeks of a plant’s life is key to yield and quality. It is all about ‘root miles.’

Assuming you have a current soil report for all nutrients that effect plant growth along with the pH and soil organic matter (SOM), what nutrients should you have analysed – P, K, Ca, Mg, Zn, Mn, Cu, B, Fe, Mo? And, if you’re planning to sow grass and clover seeds, then also consider Co and Se.

I’d advise a soil test every four to five years and if you're growing vegetables, consider sampling pre-sowing or planting.

What about ‘S’? Sulphur is very mobile in the soil and best practice would include sulphur with nitrogen. A 10N:1S ratio would be acceptable, though brassica’s would benefit from a tighter N to S ratio.

Most of the soil reports I see are low in calcium <1600mg/litre. Lime would be the least cost product to increase soil calcium levels, but bulk lime can be extremely variable in the percentage passing through 150 microns. Granular lime overcomes this problem, with 100% passing through 150 microns with a high reactivity and is ideal to lift the pH and calcium in the seed zone.

The more N that is applied, the more lime will be required. Milk, beef, lamb, venison and crops all export calcium (lime) from the soil. Do you know much calcium you are exporting? Nitrogen products are acidic – ammonium sulphate being the most acid to calcium ammonium nitrate, containing 20% lime by weight, the least. For vegetables, calcium nitrate is not acidic.

A recent trial showed an increase in production of 18% where lime was applied to increase low calcium levels. The soil pH was 6.2 and was increased to approximately 6.4 – not only was yield increased, but the feed quality of the herbage was greatly enhanced, with more DCP and ME.

Over the years, I have seen the effect in cereal crops where fertiliser was combine drilled and where it was broadcast in the same field and on the same day. The difference was chalk and cheese. Why?

Phosphate, as well as calcium, zinc, manganese and nitrogen would be the key root drivers. Phosphate has negative charge, with the other elements having positive charge.

It is well document that up to 90% of the applied P can get locked up, which is very frustrating. Trials using ‘optimised phosphate’ has clearly demonstrated an increase in ‘root miles’ and yield.

Phosphate is not mobile in the soil, maybe 0.2mm/week and would be best placed with the seed down the same spout. Check also that the phosphate you are using has a good water soluble percent. Products do vary, but remember phosphate will allow earlier growth in the spring and in colder soils.

How much nutrition are you giving each seed to allow the plant to start growth and get the roots growing down to pick the nutrients that is in the soil? For instance, if you plant six seed potatoes/sq m and your growing for the seed market, you could well be applying 150kg/ha of P2O5, or 15g/sq m which equals 2.5g/plant.

Similarly, if your soil status is 2 (moderate) and you are to establish a grass and clover mix, where the number of seed sown/sq m will be between 2500 and 3000 seeds, the recommendation would be to apply 70kg/ha P2O5 or 7g/sq m (0.0023g/plant or seed).

This means a lot plants are not going to get any starter nutrition. How many of the seeds do you sow establish? You would not do this if you were having to feed young stock.

With spring barley, if you sow 450 seeds/sq m and apply 50kg/ha P2O5, that equals 5g/sq m or 0.011g/seed. Some are going to be hungry?

Potash is major nutrient No 3, with dung and slurry valuable, but highly variable sources, so consider having it analysed. Many field are low and very low in K2O and if this is the situation, it will have big effect in the crop quality and yield.

Furthermore, a lack of potassium is like trying to run an engine without oil in the sump and the conversion of nitrogen to DM yield will be reduced.

We have two considerations to manage – 1, what is the plant uptake; and 2), how much is the crop removal.

An example:

OSR uptake over 400kg/ha – removal seed only, 11kg/t @ 5t/ha = 55 kg/ha.

Potatoes uptake over 450kg/ha – removal 6kg/t.

Grass silage uptake over 170kg/ha – removal 6kg/t @ 25% DM.

Wheat over 350kg/ha uptake – removal 10.4kg/t, including straw.

Other key nutrients:

Magnesium

Low magnesium soil levels will have an effect on yield and quality. Wheat will remove 4.2kg MgO/t; OSR, 10.6kg/t; barley 4.0kg/t; and potatoes 1.5kg/t. Growers have to ask if their fields

can support the levels required for optimum growth.

Calcium

Are your fields low in calcium? (ie <1600mg/litre). OSR will remove 5.7kg/t; wheat will take out 2.5kg/t; potatoes take away 0.5 kg/t; while a 25% DM grass equals 0.7kg/t.

Blenders, like Glasson Fertilizers, are well placed to produce products to suit most situations from there blending sites in Montrose and near Lancaster. Trial for yourself its optimised phosphate (GOP)imported from Agrotech USA, plus it has CAN granular nitrogen and all other elements as required.