Arbuscular mycorrhizae play key role for mungbeans in low phosphorus soil

Mungbean has a high arbuscular mycorrhizal fungi (AMF) dependency so there is a risk to production if growers do not adequately address phosphorus (P) nutrition. Gaps exist in current understanding of mungbean P nutrient requirements to maximise productivity, particularly if soil AMF levels are low at planting. A glasshouse trial of mungbean (cv. Jade-AU ) with factorial combinations of three AMF levels (NIL, LOW and HIGH) and eight P rates, was conducted. All mungbean plants increased in biomass and pod production as P level increased. However, lower AMF levels in the soil meant mungbean plants required higher rates of P to attain similar growth. If AMF levels are low following a long fallow of more than 12 months and/or soil P levels are deficient to low, the application of between 44 and 87 kg P/ha is required to maximise production

Mungbeans: response to applied nitrogen

Mungbeans are becoming an increasingly important component of northern grains region farming systems. Currently, most growers inoculate crops with commercial rhizobia to promote nodulation and nitrogen (N) fixation, however, poor nodulation commonly results in N deficiency and significant yield reductions. To counteract these issues a proportion of the industry apply N to maximise yield. In response, a series of eight trials were implemented to quantify the response of mungbeans under different soil N concentrations and the impact this had on N fixation, from Emerald in Queensland to Narrabri in New South Wales. There was a strong indication that mungbeans will not respond to applied nitrogen fertiliser under a wide range of environmental conditions except for low starting mineral nitrogen and high yielding conditions under irrigation. This lack of response was due to rapid mineralisation and the plants ability to fix atmospheric N if well-nodulated. All treatments utilised mineral N (starting soil N + applied N), including the 0 kg N/ha treatments which utilised from ~50 to 75 kg N/ha except for one site. The percentage of N fixation decreased as the N rate increased at both the Emerald and Hopeland summer sites with the higher N rates not fixing any N at all, supporting the concept that mungbeans will not fix N if planted in a soil with high levels of available N

Soil constraints project - an update on the economic response of long term soil amelioration strategies

Take home message • Deep ripping compacted soils appears to have short term benefits but soil collapses shortly afterwards sometimes to a worse state than the original condition • While tillage and nutrition treatments have stood out in historic wet seasons, the recent dry season indicates gypsum with ripping has improved water capture and yields • Return on investment from treatments has occurred in shorter timeframes than expected • Results from on-farm research trials indicate positive responses are soil dependent and the importance of finding the right solution for your soil

Ameliorating sodicity; what did we learn about ameliorating sodicity constraints with a range of treatments? Yield responses to ripping, gypsum and OM placement in constrained soils.

Take home message • In Qld, it appears a yield gap does exist for cereal grains with substantial positive yield increases generally from combinations of tillage and subsurface nutrient placements • In the early phases of the experiment, there has been no yield difference between organic and inorganic nutrient application but the input rates are very high. These might diverge in future as Nitrogen supply from the organic treatment might provide a longer release pattern • With generally high levels of growing season rainfall in crops grown since soil ameliorants were applied, there has not yet been the opportunity for the soil water benefits expected from amelioration of soil sodicity with gypsum to be fully expressed as yield increases

Ameliorating sodicity; what did we learn about ameliorating sodicity constraints with a range of treatments? Yield responses to ripping, gypsum and OM placement in constrained soils.

Take home message • In Qld, it appears a yield gap does exist for cereal grains with substantial positive yield increases generally from combinations of tillage and subsurface nutrient placements • In the early phases of the experiment, there has been no yield difference between organic and inorganic nutrient application but the input rates are very high. These might diverge in future as Nitrogen supply from the organic treatment might provide a longer release pattern • With generally high levels of growing season rainfall in crops grown since soil ameliorants were applied, there has not yet been the opportunity for the soil water benefits expected from amelioration of soil sodicity with gypsum to be fully expressed as yield increases

Integrating the L (learning) into PAR (participatory action research)

Declining soil organic matter, soil health and loss of natural fertility are major constraints to sustainability on Australian grain farms. Improved knowledge of soil health is required by those managing Australian soils - farmers. An extension program was delivered to Queensland grain growers in 2022/23 to develop participants' knowledge and their capacity to improve soil management. This program utilised Participatory Learning and Action Research, which combined a structured action learning approach that established on-farm participatory action research to start improving soil health. During the program over 70 properties self- assessed their soil health utilising their own soil data. Growers then identified their top priorities and new management practices they wanted to test in their paddocks. Deep placement of phosphorus was the highest rated priority and the management practice growers most wanted to test in their paddocks (49%). On-farm research sites were implemented to test and refine these practices on participants' properties