Kelly Becker, GRDC Northern Region Panellist, Theodore Qld
Protein testing grain sorghum at harvest should be routine practice if growers want to maximise the profitability of their crops.
As the grain protein content of sorghum is a reliable indicator of available nitrogen, testing grain protein levels enables growers to assess the effectiveness of their in-crop nitrogen program and weigh up whether the program delivered the best return for the dollars outlaid.
Managing the nutritional requirement of sorghum is one of the keys to ensuring the crop is as productive as possible given that nitrogen deficiency is a major limiting factor when it comes to yield.
According to the Department of Agriculture Fisheries and Forestry (DAFF), grain sorghum protein levels (at 13.5 percent moisture) of less than 9pc indicates acute nitrogen deficiency, 9-10pc indicates marginal nitrogen deficiency while levels above 10pc suggest that nitrogen is adequate and not adversely impacting yield.
Signs of nitrogen deficiency are usually evident in the older leaves which can become pale green with pale yellow chlorosis and pale brown necrosis. The development of pale yellow leaves is the most obvious symptom of nitrogen deﬁciency.
Nitrogen fertiliser application rates should be based on target yield, seasonal expectations and previous paddock history and may vary significantly from area to area and even paddock to paddock depending on previous cropping history and soil types.
Both manure and synthetic fertiliser options are available, although the price of manure will vary according to location and spreading capacity.
Recent research trials funded by the Grains Research and Development Corporation (GRDC) found that growers would maximise their crop yield potential and profitability through targeting a 9-10pc protein level.
Additionally, soil tests can be undertaken prior to planting to estimate nutrient levels and are extremely beneficial used in conjunction with records of grain production and grain protein tests to determine a nutritional program for the crop.
Using this information in association with depth of stored soil moisture, nitrogen fertiliser levels for individual crops can be estimated once a target yield has been established.
Following the crop right through from planting to harvest and making accurate assessments of nitrogen availability and utilisation is one of the best ways to account for a crop’s performance and to influence the profitability of following crops.
Protein tests are readily available through many of the commercial agricultural laboratories and can be arranged through your local agronomist or consultant.
Kelly Becker, GRDC Northern Region Panellist, Theodore
Sarah Jeffrey, Senior Consultant Cox Inall Communications