NUTRITION
At a time when budgets are tight, it is important to evaluate the cost effectiveness of every input. Fertiliser comes in many different formulations, blends and prices, but does the grass know the cost? No…
A good
feed
In the second instalment of looking at the basics of fertilising turf surfaces, AGCSATech agronomist Steve Tuckett looks at the different types of fertilisers available on the market.
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n the last edition of Australian Turfgrass Management Journal, the article ‘A good feed’ (ATM Volume 22.2, pages 56-61) looked at the fundamentals for developing a successful fertiliser programme. In this follow-up article we will examine the different types of fertilisers available to the sports turf manager, how they work and where they fit into a programme. We will also look at the calculations required for cost comparisons which is important to know for budgeting purposes when developing such programmes.
SIMPLE, SOLUBLE FERTILISERS These are chemical fertilisers, produced by industrial processes, which contain the major nutrients that are readily available to the plant. The turf manager can apply them as they are or make their own blends, or buy commercial NPK blends which are more convenient. These products are all basically salts, defined as a solid compound that will dissolve in water into its two constituent charged components – the positive ion (cation) and the negative ion (anion). Sulphate of ammonia has a nitrogen (N) percentage of 21 per cent and
the other 79 per cent is made up of crystals of (NH4)2SO4. Table 1 lists common N carriers, along with their molecular formula and percentage. Some of them also contain phosphorous and secondary nutrients including sulphur. The rate column shows how much of each fertiliser is required to deliver a standard application rate of 0.2kg/100m2 (the calculation is 0.2kg/100m2 x 100, divided by the N%). All of these fertilisers will produce a response in terms of green-up and growth. However, there are important differences between these
TABLE 1. NITROGEN CARRIERS Fertiliser Analysis Solubility g/L Salinity index pH effect Fert Rate Cost Unit Cost kg/100m2 c/kg c/100m2 Urea 46% N 1,000 75 0.75 0.43 kg 85 36 Sulphate of Ammonia 21% N, 24% S 706 69 1.1 0.95 kg 70 62 Potassium nitrate 13% N, 38% K 133 74 -0.13 1.54 kg $1.60 $2.46 Di-ammonium phosphate (DAP) 18%N, 20%P 575 34 0.5 0.95 kg 90 85 Mono ammonium phosphate (MAP) 10%N, 22%P 227 30 0.5 1.67 kg 90 $1.50 1
Adapted from Ford 2018 common nitrogen carriers
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AUSTRALIAN TURFGRASS MANAGEMENT 22.3