Ground Cover Supplement : GC Supplement - Soil constraints
11 Economics PREVENTION BETTER THAN CURE WITH DEEP COMPACTION Regular deep-ripping programs, previously considered an alternative to controlled-traffic farming, can no longer reach the deep compaction layers being caused by heavier, modern cropping machinery By James Hagan USING A STANDARD set-up of a 14-metre header, 15m seeding bar, 36m boomspray and a chaser bin not running on tramlines, between 40 and 50 per cent of a paddock can be traversed by wheel tracks in a single season causing soil compaction (tracked percentage). Ongoing soil compaction can restrict root growth and penetration into the subsoil, reducing the crop's access to moisture and nutrients, To minimise compaction the perfect set-up is a fully matched controlled-traffic farming (CTF) system with a 1:3 ratio, meaning the header and seeder are one- third the width of the boomspray. Such a system reduces wheel track coverage to just 10 to 12 per cent of the paddock. Other benefits of CTF include reduced overlap resulting in less inputs and fuel savings (Table 1). However, the relatively large size of some seeding, harvest and spraying programs, along with the width restrictions of straw, fertiliser and lime spreading, often make it necessary to compromise on the ideal CTF set-up. When larger seeding gear is required a popular compromise is a 1:2:3 system, in which the header is a third of the width and the seeding bar half the width of the boomspray (a 12m, 18m, 36m system on 3m centres). While this system is not 'perfect' it does reduce the tracked percentage considerably -- to about 18 per cent of the paddock. THE COST OF COMPACTION While the tracked percentage is important, it is the yield penalty caused by compaction that is the critical statistic to determine. Research in Western Australia suggests that yield penalties from compaction on deep sands can range from 20 to 37 per cent, while deep sandy-loam duplex soils (top layer deeper than 30 centimetres) can suffer an average 22 per cent yield penalty from compaction. The best way to calculate the possible yield benefits from moving to a CTF system is to multiply the difference in tracked percentage between the non-CTF and proposed CTF system by the identified yield penalty for the relevant soil type (Table 1). Implementing CTF on the deep sand example in Table 1 removes 27 per cent of the paddock from wheel tracks. If using an average yield penalty from compaction on deep sands of 35 per cent then moving to the CTF system results in a 9.5 per cent yield boost. MOVING TO CTF The effort required to convert to CTF may be minimal if machinery is already at complementary widths and the only necessary changes are wheel-spacing modifications to create a fully matched CTF system. For others, it may require the replacement of all machinery to create a system that works effectively. With CTF purchases worked into a standard machinery replacement program, the cost of moving to CTF can be minimised and some purchases can be brought forward once the farm business is close to reaching a full CTF match. A survey of WA growers found it cost less than $20,000 for a move to a CTF system, with moving wheel widths representing the majority of this. TABLE 1 Yield beneft from introducing a controlled-traffc farming (CTF) system to reduce soil compaction on a deep sand and loam cropping soil. Soil type Current tracked* (%) Proposed tracked** (%) Yield penalty tracked (%) Benefit of CTF (% yield increase) Deep sand 45 18 35 9.5 Loam 45 18 22 6 * Based on a standard set-up of a 14m header, 15m seeding bar, 36m boomspray and a chaser bin not running on tramlines. ** Based on a 1:2:3 system, in which the header is a third of the width and the seeding bar half the width of the boomspray. SOURCE: JAMES HAGAN, DAFWA APP PREDICTS CTF BENEFITS The Wheeltrak Calculator (www.precisionagriculture.com.au/apps- podcasts.php) can be used to compare the tracked percentage of machinery compared with matched CTF machinery. It was developed by PrecisionAgriculture.com.au in conjunction with the GRDC, DAFWA, SPAA, Condamine Alliance, Beyond Agronomy, Fitzroy Basin Association, the Australian Controlled Traffic Farming Association and Controlled Traffic Farming Alberta. Controlled-traffic farming systems can more than halve the area traversed (and compacted) by machinery wheels to deliver yield benefits of 5 to 10 per cent. PHOTO: ARTHUR MOSTEAD Wheat field demonstrating controlled-traffic system, in Young, NSW.
GC Supplement - Foliar fungal diseases of pulses
GC Supplement - Grain storage 2015