29 Feb 2012

Brookstead site - 2011 wheat results

Managing K in northern cropping systems
Brookstead research site, southeastern Queensland.

Brookstead site - wheat 2011

This site was sown to wheat in May 2011. The experiment aims to investigate K placement depth and band spacing for rainfed grains. The whole site was treated at sowing with 40 kg P (as mono-ammonium phosphate), 110 kg N and 15 kg S (as ammonium thiosulphate) as well as additional zinc. Responses to different placements were not statistically different, so that band depth and spacing were not important in the first crop after application, but in seasons with reliance on stored water, it is expected that the deeper placed K will provide a better response.

The K uptake data from the Brookstead wheat samples show better access from mixed (shallow + deep) bands, followed by shallow placement ...both in the 25 cm and the 50 cm band spacings. The value of the deep K in a pretty wet season was lower, but not unexpected given the likely root distribution in such a season.

It was also clear from the multi-nutrient treatments at this site, that attention to P and S as well as K is important. Most growers have strategies for tactical N application depending on seasons, and it is thought that the main avenue for future gains will be attention to these other nutrients.

Table 1. Responses to band depth and between-band spacing of muriate of potash (KCl) applied at 200 kg/ha 3 months before wheat planting at a site at Brookstead. Differences were not statistically significant.

Grain yield (kg/ha)
Split between shallow and deep
Bands 25cm apart
Bands 50cm apart
Bands 100cm apart
    Growth figures from the Biomass sampling at maximum biomass stage (near soft dough) did show some effects of applied K:

    Control/Farmer Practice - 5.4 t/ha biomass
    Extra P+S - 10.1 t/ha biomass
    Extra P+S + shallow K - 11.7 t/ha biomass
    Extra P+S + Deep K - 10.7 t/ha biomass
    Extra P+S + half K deep + half K shallow - 11.1 t/ha

    There was an average effect of about 10% due to the added K, with the shallow K giving around a 16% increase in growth.

Sorghum 2012/2013
The site was sown to sorghum in November 2012.

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