Ground Cover West : Ground Cover 049 April-May 2004 - West
HIGH GRAINS 30 APRIL 2004 By ALEC NICOL There is no need to convince anyone farming the estimated 50 million hectares of acid soils in the southern region high rainfall zone that liming pays. The question is, how much is enough? As the pressure comes on this country to increase the area under crop and to manage developing dryland salinity, the answer could be, “twice as much.” Incorporating 2.5 tonnes per hectare of lime is now standard practice across most of the high rainfall zone. However, results from 12 years of work in the ‘Managing Acid Soils Through Effcient Rotations’ (MASTER) project, suggest that the fgure should be at least 4t/ha and possibly more. Dr Guangdi Li, research scientist on the project, says the standard 2.5t/ha of lime is enough to neutralise the new acid in the top soil but not enough to deal with a hostile subsoil. The MASTER project is based on 15 hectares of trial plots south east of Wagga. At the start of the project the pH in the top soil was 4. Below 10 centimetres the root-inhibiting exchangeable aluminium level was 42 percent. Initially 3.7t/ha of lime was incorporated. Over 12 seasons that has been boosted to 5.4t/ha and the results have been spectacular. The pH of the top soil is now 5.5. Below 10cms it stands at 4.5, up half a unit and, signifcantly, the level of exchangeable aluminium in this zone now averages 10 percent, well on the way to the 5 percent needed if sensitive crops such as lucerne and chicory are to succeed. This has provided an unexpected beneft: “At that initial 42 percent level, root growth is virtually impossible,” says Dr Li. “During the drought we took core samples on country we hadn’t limed and found readily available moisture at 50cms. However the roots simply couldn’t get access to it so the impact of the drought on unlimed country was much more severe than where we had applied lime.” Over 12 years the trial has compared the economic returns from limed and unlimed country under a two-year annual pasture/crop rotation incorporating sub-clover and wheat – and a six-year rotation using triticale, canola, a grain legume and wheat in conjunction with phalaris, cocksfoot, sub-clover and lucerne pastures. Conventional wisdom suggests that at high levels of acidity potential production is halved. In the MASTER project, wheat yields jumped by 110 percent with the addition of lime. A cid-soil-sensitive canola crops increased yield by more than half and even the acid-soil-tolerant triticale saw close to an 80 percent increase in yield. Liming also had a signifcant knock-on effect on the performance of other fertilisers. “Acidity is more limiting on the crop than nitrogen, and may even limit the ability of the crop to make use of available phosphorus,” says Dr Li. “On the unlimed plots our grain yields increased by 10kg for every kilogram of nitrogen we applied. Where we’d limed we got double the response. “If you haven’t limed, then adding nitrogen in the cropping phase is wasting the resource and something similar could be happening with phosphorus. We’ve been applying the accepted 15kg/ha of phosphorus across all of the plots. In the unlimed area we’re seeing a build up in the level of available phosphorus. It may be that under acid soil conditions plants just can’t use the available phosphorus.” Crops are not the only things to respond to the lime – barley grass does well too. Pasture has a better balance of desirable species where the lime has been applied but barley grass is now a problem in both annual and perennial pastures: “We still have to apply a herbicide when we’re cropping, but at least we’re now dealing with something with some feed value,” says Dr Li. “Rubbish like vulpia is the dominant species where we haven’t limed.” This is primarily grazing country and increases in carrying capacity, wool cut and body weight of sheep were also outstanding. The limed country carried an additional four Dry Sheep Equivalent a hectare with an increase in wool-cut of between 14 and 36 percent. The researchers have also put considerable effort into making sure yield results outweigh the costs of achieving those results. To date, liming at the higher rate has paid when clean wool prices topped 650c/kg, and straight grazing beat cropping when clean wool prices topped 950c/kg. Outside these parameters, mixed farming is more proftable than grazing and many graziers look to the cash fow generated by cropping to pay for the addition of lime. In this case, a rotation including canola and triticale with permanent pasture seems the most economically viable path. GRDC RESEARCH CODE DAN 349, program 4 For more information: Dr Guangdi Li, 02 6938 1930, firstname.lastname@example.org By PHILLIPA BUTLER F aba beans have emerged as a better-than-expected prospect for high-rainfall areas in a surprise result from the record rainfall that deluged Tasmania last winter. It was the wettest year in 50 years, yet trial plantings of faba beans generally coped well with the waterlogging that knocked out some other crops. Even more surprising, says Tasmanian Institute of Agricultural Research (TIAR) Research Fellow Geoff Dean, is that the beans were generally grown on the fat, not on raised beds. “There were not a lot (of faba beans) grown last year but generally speaking they did well – by far the best of the grain legumes in waterlogged situations,” he says. The fact that they did well on the fat is signifcant because if there is a dry fnish to the growing season – and last year Tasmania was hit by one of its driest springs on record (decile 1 rainfall for October and November) following immediately on the wettest winter – raised beds can exacerbate the lack of moisture. “You can end up with lower yields on the beds if there is insuffcient soil moisture,” says Mr Dean. Faba bean paddock yields averaged between one tonne per hectare where they were fooded, and 3.5t/ha on less waterlogged country. From here, TIAR, which falls under the umbrella of the University of Tasmania, expects greater grower uptake of the crop, particularly in heavier soil profles. For Northern Midlands farmer Crosby Lyne, the state’s fckle weather caused few hiccups. Growing 22 hectares of Clearfeld canola on fat ground, he achieved a reasonable yield, averaging about 2t/ha. His trial plot of faba beans averaged 3t/ha. While his mixed property ‘Riccarton’ at Campbell Town is not in the wettest area, he still had above average rains. “This year Campbell Town suffered a little damage from waterlogging, but not much,” he says. Mr Lyne has grown canola for three years and is hosting a Southern Farming Systems trial site. For him, canola is a valuable feed source for bees and a good break crop for his cereal crops. Mr Dean says the unusual combination of record wet/very dry meant that many areas of the state had experienced “one of the toughest growing seasons we’ve had”. Several paddocks of canola were completely lost and had to be replanted. In the wettest areas, wheat yields were down by 50 percent. Barley and peas, generally sown in spring in wetter areas, lost the benefts of the winter rains because of the exceedingly dry fnish. He says that peas, in particular, yielded poorly. GRDC RESEARCH PROGRAM 2 For more information: Geoff Dean, Tasmanian Institute of Agricultural Research (DPI), 03 6336 5233, Geoff.Dean@dpiwe.tas.gov.au n Standard practice has been to use 2.5t/ha n MASTER project suggests that the fgure should be at least 4t/ha n Trials increase wheat yields by 110 percent with the addition of lime n Increases in carrying capacity, wool cut and body weight of sheep were also outstanding With lime, it’s hard to have too much of a good thing Faba beans star in a surprise big wet showing Few weather problems: Tasmanian faba and canola grower Crosby Lyne. Lime leader: research scientist Dr Guangdi Li.
Ground Cover 048 February-March 2004 - West
Ground Cover 050 June-July 2004 - West