Scotts receives more questions on turf nutrition at this time of year than at any other - and with the ever-increasing range of fertilizer options on the market, it's not surprising. This month, technical manager Simon Barnaby selects several from the pile:
We are looking to re-seed parts of our sward this season and would be grateful for any advice on pre seeding fertilizers.
Re seeding, turf laying and renovation of bare and thin turf areas is an essential part of the annual maintenance programme. Whilst much time is spent on preparing the soil and selecting seed or turf, choosing the correct fertilizer can make an important contribution to the successful establishment of the grass sward.
The three major nutrients nitrogen, phosphorus and potassium all have an important role to play, and of these the most important is phosphorus.
Phosphorus is present in comparatively small amounts in the soil, yet is vital for root development. Phosphorus uptake is dependent on the size of the root network and roots will develop more profusely in areas of high potassium content. Ideally, phosphorus should be placed a little deeper than the seed. In practice, this will be achieved by working the fertilizer into the seedbed.
Potash is less crucial during the early stages of the seedling development, but it is needed to control plant transpiration. However, excess potash can inhibit germination - another reason for working it into the soil.
The presence of nitrogen can help the germination of some seeds, but its main role is to promote leaf and subsequently root growth, which is stimulated when surplus carbohydrates are generated in the leaves by photosynthesis. Too much nitrogen in the early stages can result in weak and overlush leaf growth, resulting in the need to mow too early and increased risk of disease.
All of which translates, in practical terms, to an optimal formulation of 8+12+8 incorporated into the seedbed at 30 to 50 g per sq m.
We are considering trying tonic liquid feeds this year, during the season, to give the grass a boost. Whilst we are used to granular fertilizers, and understand how much of each nutrient is applied per treatment, it is not so straightforward with liquids.
You are right - liquid feeds are more complicated to calculate. This is because all fertilizer declarations are expressed as a percentage by weight, so a formulation of 11+0+11 means that 11% of the weight is N, zero P 2O5 and 11% K2O. The liquid fertilizer products, however, are sold by volume!
In order to calculate the nutrient content of our range - Greenmaster Liquids - you will need to use the specific gravity of the particular product in the calculation. They are all slightly different:
High N 1.199
Spring and Summer 1.25
To convert to grammes per litre use the equation % by weight x SG x 10
So, 11+0+11 contains:
11 x 1.28 x 10 140.8 g per litre N
0 g per litre P2O5
140.8 g per litre K2O
To calculate the kilogrammes per hectare use the equation (Application rate (litres/ha) x % nutrient content) over 1000. (sorry Nev - can't find the 'divide' sign)
So, 11+0+11 applied at 40 litres per hectare contains:
40 x 140
1000 = 5.6 Kg/Ha N
0 Kg/Ha P2)5
5.6 Kg/Ha K2O
Needless to say, the equation can be worked backwards, in order to determine the right application rate in litres per hectare) to achieve a desired total nutrient level across the sward.
Often after we have applied granular fertilizers the growth response is uneven, and you can almost see where the spreader has been. We are obviously doing something wrong - even though we have ended up applying the right amount of fertilizer for the area.
This is a common problem that stems from, essentially, the difficulty of keeping passes with the fertilizer spreader absolutely precise. Experience can help improve accuracy, but there are a couple of hints and tricks that can help.
First, always go for high quality fertilizers with narrow particle distribution. Scotts Sierraform range with Contec technology was actually developed with this problem in mind. Contec granules have a particle distribution of only 0.7 to 1.4 mm, which means that the spread predictably, evenly and very thoroughly over the sward. With double the number of granules per square metre than some large granule alternatives, nutrient provision will be inherently more accurate.
The Sierraform with Contec granules are homogeneous, too. This means that every granule contains the same nutrient ratio - no blending of granules of different make up.
Finally, in terms of actually applying the material, try setting the spreader to apply half the desired rate and then double the passes over the area. This will even out any inaccuracies in application. It is best to adopt a 'double pass' pattern over the turf in the same direction, rather than doing the second pass in a perpendicular direction to the first.
There are various fertilizers on the market that contain seaweed extracts - do they actually make any difference?
Seaweed derivatives of the type contained in the Scotts 'Longlife' range are there to encourage microbial activity in the soil and act as a source of trace elements. Although trace elements are rarely deficient in healthy turf, they do get removed with clippings and need to be replaced. Most products also contain sulphur, iron or magnesium, which not only improve turf colour, but are important components in the vital photosynthetic pathways within the grass plant.
Another option is to apply these products as a separate treatment (or tank mixed with liquid fertilizers), using something like Greenmaster Liquid Seafeed. Seafeed is a concentrated seaweed extract derived from Laminaria. It contains betaines to improve water retention and increase drought resistance, cytokinins and trace elements to increase photosynthesis and plant metabolism.
We are going to kill two birds with one stone this season and apply a combined feed and weedkiller product. Any points we should look for?
Firstly, do not apply to newly sown or turfed areas within six months of establishment. And if there are bulbs present, wait until the bulk of the foliage has died down first.
Avoid drift onto any adjacent broadleaved plantings and do not use the first four mowings as a mulch or soil conditioner until they have been composted for six months.
Try not to cut the grass for three days prior or post application, to give it the best chance to work, and if there are bare or thin patches after treatment, wait for eight weeks before over sowing.