Agronomic Review: The latest

NARROW SPACING IN CHICKPEAS Queensland researchers report using narrow-row spacing to help fight annual ryegrass (ARG) in chickpea crops. A two-year Gatton trial compared results between rows spaced 25cm apart with those spaced 75cm apart. The scientists found narrow-row spacing suppressed ARG biomass by between 16% and 52% and reduced number of ARG spikes of ARG by 26% to 48%. The researchers also reported that average yield was 20% greater with the narrow-spaced rows. More?

LONGER ROTATIONS BOOST SOC Longer rotations increased soil carbon (SOC) in a 24-year US no-till cropping trial. A four-year rotation increased SOC by up to 22%, compared with a negligible increase in the less-than two-year rotations within a 0–60cm soil profile. More? Soil Research 57(2) 149-157

COMPOST BOOSTS SOIL C Use of moderate compost increased soil carbon (C) by 20% relative to fertiliser in a 20-year trial conducted over a corn/soybean/wheat rotation by US scientists. More?

CLAY AS AN ANTIBACTERIAL US study finds antibacterial qualities in clay. More?

WEED SUPPRESSANTS NAMED Wagga-based research suggests that selected legumes can be effective annual weed-suppressants. The results from three-year field trials n NSW suggested that arrowleaf clover and Casbah biserrula most consistently suppressed annual pasture weed species, but also that yellow serradella ‘Santorini’ suppressed more weeds while producing lower biomass. The researchers reported that the serradella used another mechanism “other than competition for resources”. More?

MULCH SOAKS UP RUNOFF N Applying mulch to low-lying areas helps soak up excess nitrogen (N) before leachate reaches waterways. US Government research saw 65 to 69% of N loads reduced from runoff. Researchers suggested hardwood mulch applied to agricultural ditches could offer a simple, low-cost option. More?

STUBBLE HEIGHT/HEAT LINK University of Tasmania research suggest that pasture persistence is compromised in hotter temperatures by defoliating to shorter stubble heights. A rainfed experiment in north-west Tasmania amid temperatures at 30+deg over two summers saw shorter heights linked to crown average temperature increases of 4.2°C for perennial ryegrass, 3.6°C for tall fescue and 1.8°C for chicory. Their lower temperatures might partly explain why chicory and second-year tall fescue swards often outyield perennial ryegrass in hotter summer environments, the researchers reported. More?

SOIL ZOO AFFECTS DROUGHT RESPONSE A scientific review has revealed pasture response to drought is affected by soil microbes, flora and fauna. The NZ AgResearch study reported that increasing pasture diversity and soil organic matter might help mitigate the effects of drought in grassland systems. It also reported that drought-breaking rains often create a flush of nitrogen, carbon, and phosphorus that could leach into runoff. Flush magnitude is influenced by the drought’s duration, soil temperature, degree of drying, and rate of rewetting, according to the report. More? Soil Research 57(2) 101-112

RECYCLING GYPSUM FOR AG Gypsum reclaimed from defunct coal-fired power plants is showing promise as an agricultural additive, according to US research. The scientists report that the particles are small and uniform in size, making them quite reactive. “We also determined that it is safe for agricultural use,” said Professor Emeritus Prof Warren Dick at Ohio State University. “Reusing it for agricultural purposes, instead of putting it in landfills, provides multiple wins.” More?

COVER CROPS AID WUE Large-scale crop residue removal could negatively affect soil/water dynamics, improving water use efficiency (WUE). Integrating cover crop with crop residue management can help offset potential adverse effects, according to US research. More?

LIGHT RIGHT FOR N Researchers are measuring the wavelengths of light reflected off leaves to fine-tune nitrogen (N) fertiliser regimes. They use light sensors to capture reflectance data from the plant canopy; the measurements serve as proxies for crop health. The goal is to match N supply with crop need, said Yuxin Miao, a University of Minnesota agronomist. “It reduced overall N fertiliser application. It also decreased N loss into the environment and lowered nitrous oxide emissions.” More?

ORGANIC BOOSTS SOIL HEALTH Polish researchers report that organic cropping management much-better maintained soil organic matter (SOM) and soil fertility compared with conventional methods. The researchers from Poland’s Institute of Soil Science and Plant Cultivation trialled a system using no mineral fertilisers or pesticides with one using both mineral fertilisers and plant protection chemicals. Organic soils showed 16% more SOM and 25.6% more particulate organic matter in the top 5cm from 23-year-old experimental fields under winter wheat. More? Soil Research 57(2) 124-131

LEFT-OVER N FROM CROPS Crops cease taking up nitrogen a month or more before harvest maturity, and residual nitrogen (as nitrate) commonly leaches downward >1 m between autumn and spring in the humid mid-Atlantic region. US researchers found that a significant amount of nitrogen remained in the 0-210 cm profile following summer crops, more than half of which is likely to be out of reach to next year’s summer crop. More?

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