Building on duplex soils
A need to maintain cash flow has seen a greater number of wheat crops in wheatbelt cropping rotations, with the trend set to continue until the system proves uneconomical.
Current price and yield relativities that favour wheat are driving the trend to a flexible cropping sequence on duplex soils, largely sand over clay, rather than a fixed crop rotation system.
There is no real reason why duplex soils should deliver lower yields than ‘better’ soils, according to GRDC Crop Doctor, Managing Director, Peter Reading.
“Higher yields appear more dependent on early sowing and higher seed rates than on sandplain and clay loam soils where responses to improved varieties and nitrogen fertilisers play a greater role in yield improvement” he said.
“Soil constraints must always be addressed, regardless of crop sequence. Many duplex soils suffer from acidity, soil compaction and poor drainage. Some will be further exacerbated by continuous cropping and a narrow range of crops in the sequence.”
Mr Reading said possible solutions for poor or declining productivity would be to consider amelioration treatments such as liming, deep ripping and gypsum, tramline farming, claying, green manuring or raised beds.
“Most duplex soils have a bleached sand or gravel layer overlying the clay subsoil and this is often associated with transient waterlogging, root destruction, impaired nutrient uptake and leaching of soluble nutrients out of the root zone,” he said.
Although waterlogging may not affect wheat more than other crops or pastures, it suggests solutions other than simply changing the crop sequence may be appropriate.
Less reliable yield responses to applied nitrogen on duplex soils, due to poorer uptake, makes nitrogen application to second and subsequent wheat crops more expensive than with other soil types.
Date of Publication: 15 Jul 04 4:16pm ACST
Source: ezigrain Journalist
