Soil Expedition to Great Gilgandra Ground

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As the season starts to edge to a close, made quicker by the 4 days of above 35 degrees C, it’s still a great opportunity to get down some holes and see what the crops have been able to draw on for the season.
This week took us on a Soil Expedition to Dubbo and Gilgandra, NSW.
We were into 2 main soil types, black cracking clays, and hard-setting acidic red brown earths both having their constraints.
The red soil was an acidic profile with pH decreasing to 5.0 in the 5-12cm region, then had a strongly bleached A2 horizon (white layer), sitting over a clay base.
Over the season, water ‘perches’ above the clay layer and leads to water logging of the surface soil horizons. Due to the acidic conditions and the impact of water logging, nutrient efficiency is limited.
The Bleached layer highlighted the limits of the major root growth with only isolated channels of root growth developing into the B horizon through old cracks and root channels which were few and far between.
The 0-40cm top of this profile was very hard-setting and would benefit from increase in organic carbon levels (currently 0.8%OC) and also deeper fracturing to create pores and channels for early root growth.
The second pit was a brilliant deep vertosol that was cracking from 0-1.2m as the soil dried down. This soil was a high pH (alkaline) soil that had ‘free lime’ to the surface.
Phosphate availability as well as micronutrient availability were a couple of key points of focus. Sulphur was also limiting in this soil type.
Sodium accumulated at depth in the profile and the soil was moist and mouldable at 1.2m.
Nutrient management in these soils can be challenging however are responsive. In-furrow and foliar management provides responses required to impact yield.
It was great to get up around the Gilgandra region, some brilliant looking crops that are all currently filling well. Shaping up to be a good harvest, even though like many areas, Spring rainfall has been a limiting factor.
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