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DEVELOPING ROOT ZONE MANAGEMENT STRATEGIES TO MININIZE WATER AND FERTILIZER WASTE: THE UNITED STATES PERSPECTIVE WITH EMPHASIS ON SURFACE APPLIED NON-RECIRCULATED SYSTEMS
Establishment and regulation of nutrient efflux limits are imminent in America and Europe.
The lead time is already short for averting disruptive effects of such regulations on commercial production.
Contribution of nitrate to drinking water supplies, phosphate and nitrate to surface waters where eutrophication would be induced, or salts in general to any water supplies will be targeted.
Conservation of water in general is of further importance because any reduction in the quantity of usable water will lead to price increases and, consequently, economic problems for our industry.
A rarely calculated implicit cost of improper fertilizer management is yield loss.
Random periods of adversely high and low nutrient availability take their toll on plant quality and yield.
Costs of superfluous fertilizer should also considered.
Several production cost studies have identified the cost of total fertilizer used (Table 1). The identified fertilizer costs range from 0.45 to 1.27% of total production costs with an average of 0.73%. Many of these values appear to be lower than expected.
Typically, a chrysanthemum crop in 17 cm azalea-type pots would be fertilized weekly with 700 ml of a solution containing 600 mg N per liter over a crop period of 11 weeks and would receive 23 grams of a 20% N fertilizer.
At a current value of $0.002 per gram this would cost $0.046. If the pot cost $3.50 to produce, fertilizer would represent 1.32% of the total production cost.
Conservation of one third of the fertilizer used in greenhouses should be easily attainable.
This would represent production savings of 0.24% and 0.44%, depending upon which cost figure above is used.
Although this may seem insignificant, for a grower realizing a 15% return on investment these savings would translate into profit increases of 1.6% and 2.9%, respectively.
This is an excellent way to increase profits
Table 1 – Fertilizer cost as a percentage of total production cost per pot or flat for various crops.
| Fert. Cost | | ||
| Production | |
| Crop | Cost ($) | ($) | (%) | Reference |
| bedding plant | 4.587 | 0.022 | 0.48 | Brumfield (1985) |
| pot mum | 3.07 | 0.02 | 0.65 | Stathacos & White (1981) |
| Easter Lily | 2.79 | 0.02 | 0.72 | Stathacos & White (1981) |
| Easter Lily | 1.781 | 0.008 | 0.45 | Brumfield et al. (1981) |
| geranium | 0.89 | 0.005 | 0.56 | Nelson & Brumfield (1982) |
| geranium | 0.79 | 0.01 | 1.27 | Stathacos & White (1981) |
| poinsettia | 3.07 | 0.02 | 0.65 | Stathocos & White (1981) |
| poinsettia | 3.412 | 0.03 | 0.88 | Roberts & Chatfield (1982) |
| poinsettia | 3.775 | 0.035 | 0.93 | Wolnick (1988) |