Inputs and application for cut flowers
Case 1 Calcium through the fertigation - 1
Pick the plot first Open a new chat and tap Plots (All) under the question box. Choose the plot you want advice for. ORTH then works from that plot’s crop, variety, soil and documents, and from the farm weather. For cut flowers Pick one greenhouse plot of one variety. We picked Lote 1: Freedom, a red rose, on 0.48 ha under greenhouse at about 2,550 m, 31,200 plants from June 2021, loam soil and drip. Every number below is for that plot. - 2
Work out the dose for the plot We asked for 3 kg of calcium per hectare in one fertigation. The source is calcium nitrate with 15.5% N and 19% Ca, in a 1,000 L stock tank, and the injector draws 1 L of stock per 100 L of water. For the 0.48 ha of Lote 1 that is 1.44 kg of calcium, so 7.58 kg of calcium nitrate, which brings 1.17 kg of nitrogen, or 2.45 kg N per hectare. Emptying the full 1,000 L tank at 1:100 takes 100 m³ of irrigation water, 20.83 mm over the plot. ORTH flagged that as far larger than the usual events on Lote 1: do not irrigate extra just to empty the tank; size the stock to the planned event. - 3
Make only the stock the event can carry This week’s events on Lote 1 are 4.5 to 17.6 m³, so we asked how to get the full dose out in one of them. ORTH kept the 7.58 kg and sized the stock to the event: final stock volume in litres is the event volume in m³ times 10. For 4.5 m³ that is 45 L of final solution at 168.42 g of calcium nitrate per litre; for 17.6 m³ it is 176 L at 43.06 g per litre. Either way the plot gets 1.44 kg of calcium and 1.17 kg of nitrogen. For the 17.6 m³ event: put part of the clean water in the tank, start the agitator, dissolve the 7.58 kg slowly, top up to 176 L of final solution and inject all of it during the event. - 4
Leave time for clear water Those volumes assume the injector runs for the whole event, with no clear water before or after. If part of the event has to stay free of fertilizer, subtract it: stock = (event volume − pre-wetting and flushing water) × 10, with the same 7.58 kg in a smaller, stronger stock. Base that clear water on the measured volume it takes for fertilizer to reach the farthest emitter and be flushed out again. ORTH favored the 17.6 m³ event over the 4.5 m³ one: the feed is much more dilute and the risk of a sharp jump in root-zone EC is lower. Confirm the real injector draw and measure the EC of the fertigated water at the first and the farthest emitters. - 5
Keep calcium apart from sulfate and phosphate We asked whether magnesium sulfate and monopotassium phosphate can go in the same tank. ORTH said no: with calcium nitrate they form calcium sulfate and calcium phosphate, which take nutrients out of solution and can block the injector, filters and emitters. Tank A takes calcium nitrate alone. Tank B takes magnesium sulfate and monopotassium phosphate, only after a jar test with your own irrigation water and concentrations. With one tank, inject them as separate batches: rinse the tank and injector in between and run clear water through the lines before you switch from the calcium batch to the sulfate and phosphate batch. Never let the concentrates meet before dilution. Wear gloves and eye protection, add fertilizer to water, and stop injecting if the stock or an emitter sample turns cloudy or shows sediment. Case 2 A spray product to check first - 6
Check the registration and the label For downy mildew we asked about Revus, mandipropamid 250 g/L, on roses in Colombia, sprayed with lances at 1,500 L/ha from a 400 L drum. ORTH found REVUS 250 SC in the ICA national registration list with rose among its crops. That entry does not confirm the downy mildew use, the rose rate, lance application at 1,500 L/ha, the re-entry interval or the cutting interval, so those have to come from the current registered label. A Colombian supplier publishes 0.60 to 0.75 L/ha as a general rate. ORTH treated that as a conditional reference until the label confirms it for roses and downy mildew. - 7
Work out the batches, mix only after the label ORTH worked out the spray volume: 0.48 ha at 1,500 L/ha is 720 L, or 1.8 drums, so a first batch of 400 L for 0.2667 ha and a second batch of 320 L for 0.2133 ha. If the label confirms 0.60 to 0.75 L/ha, the plot takes 288 to 360 mL, the first batch 160 to 200 mL and the second 128 to 160 mL. Do not mix from these figures until the container label confirms that rate for roses against downy mildew and allows lance application at your water volume. - 8
Plan around daily cutting Roses are cut every day, so the intervals decide when people go back in. ORTH could not verify a Colombian label value for the re-entry interval or the cutting interval. Until the re-entry interval has passed, nobody goes in to cut, scout or handle foliage. A missing food-crop harvest interval does not mean export flowers can be cut straight away. Schedule the spray only once the label’s exact re-entry interval and any flower-cutting restriction are confirmed, and check the US and EU buyer protocols, which may add restrictions beyond the ICA label. ORTH asked for a clear photo of the current label with its ICA number, rose-use table, rate, re-entry interval and restrictions to finalize the batches and the next safe cutting time. Follow the label, PPE and entry controls, and protect workers, beneficials and water.
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