Crop and Pasture Science Crop and Pasture Science Society
Plant sciences, sustainable farming systems and food quality
Table of Contents
Crop and Pasture Science

Crop and Pasture Science

Volume 68 Number 1 2017

It is important to determine how agronomic practices, for example altering plant population density (PPD), affect stalk-sugar yields of newly developed sugarcorn hybrids for dual-purpose bioenergy–silage crop production in short-season regions unable to grow sugarcane. Increasing PPD from 75 000 to 125 000 plants ha–1 increased stalk sugar concentrations and produced sucrose yield of up to 3.8 Mg ha–1 in some of the sugarcorn hybrids. A PPD ≥100 000 plants ha–1 is required for the dual-purpose use of sugarcorn hybrids.

The capacity for several new and existing short-term forage legumes to contribute N benefits for subsequent grain crops was evaluated at four locations in southern Queensland. Legume N fixation was found to be sensitive to high soil mineral N, but lablab, burgundy bean and sulla were estimated to fix up to 150 kg N/ha and increase soil nitrate available for subsequent crops. This work demonstrated that new legume options can provide greater N benefits in farming systems compared to traditional ley legume options and annual forage grasses.

There is a growing need to select soybeans that are tolerant to herbicides other than glyphosate, in order to combat weed resistance and provide alternative weed control in soybean production. Sulfonylurea herbicides offer many advantages and exert their effect by inhibiting a key enzyme in protein synthesis. By using soybean seeds of different sulfonylurea tolerance and a proteomics approach, we showed that many more proteins were affected in the sulfonylurea-susceptible soybean as a result of sulfonylurea treatment.

CP16098Soilborne root disease pathogen complexes drive widespread decline of subterranean clover pastures across diverse climatic zones

Kevin Foster, Ming Pei You, Brett Nietschke, Nick Edwards and Martin J. Barbetti
pp. 33-44

A survey undertaken in 2014 to define the levels of soilborne disease and associated pathogens in annual subterranean clover pastures across the different agro-geographical regions of southern Australia established that tap and lateral root diseases are widespread and severe, having devastating impact on the feed gap during autumn–early winter. Severe root disease was independent of the highly variable complex of soilborne pathogens associated with diseased roots, geographic location and rainfall zone. It is evident that soilborne root diseases are the primary factor responsible for widespread decline in subterranean clover productivity of pastures across southern Australia. Implications for disease management and options for extension are discussed.

CP16279Response of Digitaria insularis seed germination to environmental factors

F. H. Oreja, E. B. de la Fuente and M. E. Fernandez-Duvivier
pp. 45-50

Freshly harvested seeds are non-dormant and the best conditions for germination are fluctuating temperatures of 20-35°C. At constant 25°C, germination increases with the number of hydration-dehydration cycles and decreases with far red light for 1 h. Reducing soil thermal fluctuations and/or far red: red ratio (stubble, cover crops, etc.), could reduce seedling emergence for this species.

New tall fescue cultivars have been selected for leaf softness in an effort to improve animal intake and performance. To exploit the expected superior nutritive value, an appropriate understanding of the leaf morphogenetic factors that determine nutritive value is needed. The work showed the effect of leaf age and length on leaf fibre digestibility. Results were conclusive about the relevance of the defoliation management in relation to the leaf turnover.

Signal grass is a key forage for the Brazilian livestock industry but its management under grazing has been empirical and suboptimal. Grazing based on canopy targets was evaluated for forage yield, morphology and nutritive value. To optimise leaf yield and forage digestibility, signal grass should be grazed to a 10-cm stubble when canopies reach 18–30 cm (95–100% light interception), suggesting that traditional fixed-rest grazing can evolve to recommendations based on canopy target.

CP16176Modelling of lucerne (Medicago sativa L.) for livestock production in diverse environments

Andrew P. Smith, Andrew D. Moore, Suzanne P. Boschma, Richard C. Hayes, Zhongnan Nie and Keith G. Pembleton
pp. 74-91

The GRAZPLAN model for lucerne was further developed and comprehensively validated. Changes in the overall representation of plant phenology ensured agreement between modelled and observed data for different genotypes types with varying winter activity. The model is suitable for use with the spectrum of different genotypes, climates, soils and farming systems based on lucerne in Australia.

The aim of this study was to understand the adaptive strategies of Bromus danthoniae to a hyper-saline environment using 80 genotypes. Salinity treatments of 0 and 350 mM NaCl were applied for 4 weeks, and physiological traits were evaluated. A coincidence of low concentrations of Na+ in the leaf tissues and the excretion of salt crystals on the sheath leaves and leaf blades was observed in the hyper-salinity tolerant genotypes.

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