Ground Cover Supplement : GC Supplement - Profit from crop nutrition 2013
Northern region 10 SOIL TESTS AT DEPTH PAY DIVIDENDS IN DEFICIENT CROPPING SOILS Nitrogen applications can be wasted even on deficient cropping soils if the levels of other nutrients such as potassium, phosphorus and sulfur are not optimised. “The importance of treating all nutrient deficiencies was highlighted in experiments we carried out over the 2012-13 summer at Capella and Gindie in the central highlands of Queensland,” Dr Mike Bell says. The trials were established to determine the most effective rate of nitrogen fertiliser for sorghum crops grown in a 1.5-metre row spacing. Sorghum was sown into a full moisture profile and received good in-crop rainfall – 240 millimetres at Capella and 320mm at Gindie. With low starting nitrate contents (30 to 40 kilograms of nitrate nitrogen per hectare) and excellent soil moisture, both sites were expected to respond well to the 70 to 85kg of nitrogen fertiliser applied per hectare. “Sorghum yields at Capella increased by 85 per cent in response to the additional nitrogen, but we were surprised to find no yield response to nitrogen at Gindie,” Dr Bell says (Figure 1). Dr Bell discovered that the lack of response to nitrogen at Gindie (despite its low availability in the soil profile) was caused by limited availability of potassium in the 10-to-30-centimetre soil layer. “Growers following normal district fertiliser practice on the Gindie soil type in 2012-13 would have missed out on 1.4 tonnes/ha of sorghum in a high-profit year as well as wasting about 50kg of nitrogen per hectare,” Dr Bell says. “A soil-testing program to detect limiting nutrients at depth would have been money well spent.” BEWARE MULTIPLE NUTRIENT DEFICIENCIES As soil nutrient reserves decline, it is essential to match nutrient combinations to crop type and seasonal conditions to maximise crop productivity and water use efficiency. Ongoing More Profit from Crop Nutrition (MPCN) research in Central Queensland is unravelling how crop type and seasonal conditions interact with multiple nutrient deficiencies at depth to affect crop yield. Trial sites at Capella and Gindie, in Queensland, established with support from the International Plant Nutrition Institute and Canpotex, have low phosphorus, potassium and sulfur especially in subsoil layers. Dr Mike Bell and colleagues have established trials in which a single nutrient (phosphorus or potassium or sulfur) or combinations of phosphorus, potassium and sulfur, are applied into the 10-to-30- centimetre layer. Plots were sown to sorghum (2012) then chickpeas (2013) at Gindie, and wheat (2012) then chickpeas (2013) at Capella using typical commercial practice (Figure 2). “Early results are showing that nutrients can have either single or additive effects on yield and that different nutrients can become limiting according to the season or crop type sown,” Dr Bell says. Dr Bell says the 2013 yield results from the Gindie site were particularly interesting. “While the 2012 sorghum crop responded only to phosphorus, the 2013 chickpea crop showed a significant response to potassium (27 per cent increase in yield).” In addition, the additive effect of the residual phosphorus and potassium were substantial with a 51 per cent increase in 2013 chickpea yield compared with unfertilised plots. Dr Bell believes the potassium response in the 2013 chickpea crop could be related to seasonal conditions as there was no effective in-crop rainfall to enable access to shallow potassium reserves. “It could also be that chickpea requires more potassium than sorghum but we just don’t have that information yet,” Dr Bell says. Other factors influencing the crop responses could be agronomic factors such as row spacing, which in turn influence available soil volume for root exploration. “We are currently exploring these interactions in the second phase of the MPCN program.” Nutrients were applied in 20cm-deep bands, 50cm apart. Data are shown for grain yields in consecutive crops grown in 2012 and 2013. FIGURE 1 Impact of added soil nitrogen on sorghum yields at two Queensland central highland sites (Gindie and Capella) in 2013. Capella Gindie Grain yield (t/ha) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 N rate (kg/ha) SOURCE (Figures 1 and 2): Mike Bell, Queensland Alliance for Agriculture and Food Innovation 0102540557085100 FIGURE 2 Crop yield response to P, K or S fertiliser (either alone or in combination) during the 2011 fallow period at two sites in Central Queensland. Control K P PK PKS Grain yield (kg/ha) 4000 3500 3000 2500 2000 1500 1000 500 0 Gindie sorghum Capella chickpeas Gindie chickpeas Capella wheat 20% response to deep P 20% response to deep P 14% response to deep P 27% response to deep K 51% response to deep P+K 8% response to deep P 13% response to P+K Grain 2012 Grain 2013 Although both sites were nitrogen deficient there was no response to added nitrogen at Gindie due to an undetected deficiency of potassium in the 10 to 30cm soil layer.
GC Supplement - Farm business management 2013
GC Supplement - Frost