Ground Cover Supplement : GC Supplement - More profit from crop nutrition II
18 On-farm CASE STUDY NUTRITION DRIVES YIELD PURSUIT By Rebecca Jennings DARLING DOWNS GROWERS Glenn and Carol Milne's underlying philosophy is to "farm water". Obtaining maximum infiltration of rainfall and the maximum grain yield from the available water is paramount on their 600-hectare farm near Dalby in southern Queensland. The farming system is designed to achieve these goals, with a zero-till, controlled-traffic system (on three- metre centres) with GPS guidance. "I'm an optimist when budgeting for yields," Glenn admits. "I use results from research to provide me with information to determine my nutrient inputs that will cater for high crop yields." While soil testing plays a role in Glenn's strategy, he also considers how nutrients are removed from the system during grain production and uses budgeting for nutrient demand. "I am targeting accurate replacement of elements removed in grain produce, but recent research has indicated a wide variation in grain nutrient content so I plan on testing grain nutrient levels in the near future," Glenn says. NITROGEN Glenn calculates the rate of nitrogen inputs each season by budgeting crop demand. For example, sorghum grain contains approximately 17 kilograms of nitrogen per tonne. With crops yielding up to 12.5t/ha, the nitrogen removal rate can reach 200kg/ha. Glenn's sorghum crops usually have grain protein of 10.5 per cent or more, which is above the yield-limiting level. Nitrogen fertiliser is the biggest single expense in the business, so any strategy that can reduce this cost is important. "Introducing more pulse crops into our farming system has reduced the total expenditure for nitrogen fertiliser on a farm basis but not on a per hectare basis," Glenn says. "I don't calculate any nitrogen contribution from previous pulse crops in the nitrogen budget for subsequent cereal crops -- this is a bonus that may benefit yields if the season is better than expected." PHOSPHORUS Soil on the Milnes' farm is naturally high in phosphorus: above the critical levels at which a yield response is expected in both the topsoil and subsoil. However, Glenn applies phosphorus at crop- removal rates in a two-step process. A monoammonium phosphate (MAP) zinc product will be applied in the fallow at 40kg/ha in what will become the planting row. At planting of pulse crops, a liquid phosphorus plus chelated zinc fertiliser is mixed with the rhizobium inoculant and is water-injected at 100 litres/ha.* For cereal crops, liquid phosphorus plus zinc is applied with a soil insecticide. Glenn uses manure from a local feedlot as a source of phosphorus, potassium and micronutrients on his irrigation country. SULFUR Soil sulfur levels at the Milnes' farm are low (typically less than 2 milligrams/kg) but crop yield responses to applied sulfur in research trials are rare. However, to replace the sulfur that is being removed, he applies a granular elemental sulfur product. "Again, I am targeting replacement of elements removed in grain produce and covering any potential deficiencies under all season types," Glenn says. He is particularly diligent with respect to the nutrition of pulse crops, on the basis that high-value chickpeas and mungbeans are worth extra attention to detail when it comes to all inputs. Glenn's chickpea yields have reached 3.5t/ha and, after participating in Queensland Pulse Agronomy Initiative trials, Glenn is a firm believer in the benefits of narrower row spacings. In the search for even higher yields, Glenn trialled a double-planting technique to reduce his row spacing from 75 to 37.5 centimetres and intends to continue using the narrower spacing. With new resistant chickpea cultivars, ascochyta blight is of less concern with narrow row spacing. Mungbeans have also found a regular place in Glenn's cropping regime and are delivering high returns thanks to record prices and yields of about 1.25t/ha. Glenn applies a nutritional seed treatment because he has seen a yield response of at least 10 per cent. He is also conscious of rhizobial innoculation of pulses -- without this, he has seen yields reduced by up to half. Looking ahead, Glenn is considering growing pulse crops on long fallows, in which case he will maximise phosphorus and chelated zinc application to help avoid long-fallow disorder. □ G RDC Research Codes DAQ00183, UQ00067 More information: Glenn Milne, firstname.lastname@example.org *Mixing rhizobium inoculum with zinc fertilisers is not recommended as best practice because high concentrations of zinc is known to be toxic to the bacteria when mixed directly with the inoculum. Research on a GRDC-supported project is investigating whether zinc in a chelated form is less toxic and therefore compatible with rhizobia. PHOTO: GRDC Glenn Milne uses a zero-till, controlled-traffic farming system with GPS guidance.
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