Fertiliser economics: liquids v solids

Waimarino Bulletin, Volume 3, Issue 23, 29 October 1985, Page 13

Fertiliser economics: liquids v solids

There is currently a big drive to get farmers to use what appears to be lowcost liquid fertiliser as an alternative to more traditional solid products such as Cropmix, DAP, urea and superphosphate. Most liquid fertilisers do have a nitrogen: phosphate: potassium: (N:P:K) rating, and I'm not debating that issue. The problem is that, at the recommended application, rates, very little N:P:K is actually applied. This is highlighted in Table 1 where all products cost around $22/ha. The table shows that at least six times more nitrogen, 24 times more phosphate and 16 times more potassium is applied for the same cost when using a solid fertiliser. PHOSPHATE A decision on fertiliser use needs to be based on the nutrients required for plant growth. Phosphate is an essential nutrient for plants, especially clovers. Clovers in turn utilize the phosphate for their own growth, producing plant-available nitrogen. This nitrogen is then utilized by grasses. Soils in the Waimarino are deficient in phosphate and about 20kgs per hectare must be applied on pastures every year. Products commonly used for maintenance phosphate are shown in Table 2. Longerlife Super is the cheapest and Dicalcic the

most expensive of the solid super-based fertilisers. It is obviously prohibitive to use liquid fertilisers for maintenance phosphate. BOOST Nitrogen can be used to give a short-term lift to pasture production, and is often used in the early spring on hay paddocks or on cereal crops at the 3-5 leaf stage. Optimum economic response for pastoral use requires around 25kg of nitrogen per hectare. Commonly used products are shown in Table 3. The cheapest form of nit-

rogen is urea applied in the solid form. DAP looks expensive but when the amount of phosphate is deducted from the cost it becomes much cheaper. Liquid fertilisers are far too expensive to get the required 25kg of nitrogen per hectare. CEREALS A boost to cereal crops requires around 10kg of nitrogen at the 3-5 leaf stage. A common practice is to mix liquid fertiliser with the weed spray. From the costing in Table 3 the cheapest liquid product is liquid urea, requiring around 45 L per

hectare for a cost of $15.30 ($6.20 per acre). The costings highlight how expensive liquid fertilisers are compared with solid products. My advice to farmers is to look closely at what nutrients are required, whether for pasture, cereals or feed crops, and use the cheapest product available on the market. With current financial returns on farms down this coming season it is vital that every dollar is put to optimum use.

Will

Wilson

Farm Advisor Waimarino County

LIQUID PRODUCTS SOLID PRODUCT Wuxal Peters Foliar Feed Cropmix 1 3 9-4-6 26-7-10 13-14-14 Recommended Rate: 6L/ha 4 kg/ ha 48 kg/ ha Nutrients Applied Nitrogen 0.54 kg/ha 1.08 kg/ha cf 6.24 kg/ha Phosphate 0.24 kg/ha 0.28 kg/ha cf 6.72 kg/ ha Potassium 0.36 kg/ha 0.4 kg/ha cf 6.72 kg/ha Cost per Ha $21.66 $22.00 $22.00 (Product only)

TABLE 1 – NPK

PRODUCT RATE APPLIED COST PER HECTARE Longerlife Super 222 kg/ha (1.8 cwt/ac) $54.30/ha Superphosphate 250 kg/ha (2 cwt/ac) $58.30/ha DAP 100 kg/ha (0.8 cwt/ac) $58.35/ha Dicalcic Super 500 kg/ ha (4 cwt/ac) $81.75/ha Liquid Fertiliser 258 kg/ha (2 cwt/ac) $1431 /ha

TABLE 2 – MAINTENANCE PHOSPHATE

PRODUCT RATE APPLIED COST PER HA Urea 55 kg/ha (0.44 cwt/ac) $29.15/ha DAP 140 kg/ha (1.12 cwt/ac) $81.62/ha Liquid Urea 113L/ha $48.40/ha v Liquid Fertiliser 92 kg/ ha (0.74 cwt/ac) $520.60/ha equivalent

TABLE 3 – NITROGEN