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

Crop and Pasture Science

Volume 62 Number 11 2011

In southern Australian, rain that falls during summer prior to the establishment of winter crops has not traditionally been valued as a resource for crop production. The millennium drought and a predicted increase in the proportion of summer rain under future climate patterns have stimulated a re-evaluation of this notion. We used a crop production model to demonstrate that summer fallow rain contributes 1.0 t/ha or 33% of mean simulated wheat yield across southern Australia.

Dual-purpose crops provide vegetative biomass for livestock and later grain at maturity. Grain yields of grazed crops in past experiments range from –35% to +75% (relative to ungrazed controls). Yield reductions are caused by poor leaf area development and delayed maturity, whilst yield increases are caused by reduced lodging or mitigation of foliar disease. To minimise effects of grazing on crop productivity, terminating grazing before growth stage 30, matching crop phenology to environment-type and ensuring good crop establishment are recommended.

Are rainfed grain crops more productive if they are grazed at heavy stocking intensities for short durations, or at light stocking intensities for long durations? We found that heavy intensities for short periods were conducive to greater recovery, and that to maximise crop productivity, grazing termination date was more important than stocking intensity. Earlier termination of grazing allowed greater regrowth of leaf area and earlier canopy closure, reducing crop water lost by soil evaporation.

Livestock grazing of grain crops may improve light distribution profiles within crop canopies and increase crop dry matter produced per unit light intercepted (radiation-use efficiency). We showed that grazing of rainfed wheat reduced cumulative light interception but did not affect average radiation-use efficiency over the crop lifecycle. Despite reduced light interception, potential yield penalties caused by defoliation were mitigated due to increased partitioning of assimilate to spikes, which was manifest by delayed phenology and extended green area duration.

Crop production in south-western Australia is restricted by increasing occurrence of potassium (K) deficiency, but the role of soil sodium (Na- salinity and sodicity) levels in K responses by cereals is not known. In salt-tolerant barley, moderate Na supply to low K soil increased shoot growth and Na accumulation but not root growth. Soil K deficiency also reduced root growth more than shoot growth in all genotypes. Therefore, crops experiencing salinity and K deficiency are likely to be more vulnerable to drought stress.

CP11232 Genetic diversity and population structure of Eurasian populations of reed canarygrass: cytotypes, cultivars, and interspecific hybrids

Andrew R. Jakubowski, Randall D. Jackson, R. C. Johnson, Jinguo Hu and Michael D. Casler
pp. 982-991

The population structure of 83 wild accessions of reed canarygrass collected throughout Eurasia, 24 cultivars from North America and Eurasia, and two accessions of phalaris was investigated. There was little geographic structure to wild populations in Eurasia, a high level of diversity present across all cultivars, but low diversity within modern low-alkaloid cultivars. These results suggest that efforts to develop cultivars for use as a biofuel feedstock should incorporate germplasm from wild material and older cultivars into their breeding programs.

CP11229 Soil phosphorus supply affects nodulation and N : P ratio in 11 perennial legume seedlings

Jiayin Pang, Mark Tibbett, Matthew D. Denton, Hans Lambers, Kadambot H. M. Siddique and Megan H. Ryan
pp. 992-1001

Developing new perennial pasture legumes for low-phosphorus (P) soils is a priority for Australian Mediterranean agroecosystems. The objective of this study was to investigate the influence of soil P supply on plant N status and nodule formation in 11 perennial legumes. The flexibility of the novel pasture legumes in this study to adjust their leaf N concentrations under different levels of soil P suggests their potential as pasture plants in low P soils in Australian Mediterranean agroecosystems.

TOC Abstract: Glyphosate is an essential herbicide for effective, safe and relatively inexpensive weed control in Australian cropping systems. It is important to understand what weed species and weed control practices are likely to lead to the development of weeds that can no longer be controlled with glyphosate (glyphosate resistance). We have created a framework which will enable growers to determine which species are at risk of developing resistance, and management practices which will prolong the effectiveness of glyphosate.

Grasses can obtain benefits through the mutualistic symbiosis with asymptomatic fungal endophytes. We found that the endophyte inhibits seed germination but, at the same time, it improves survival of red fescue seeds. Our results support the use of fungal endophyte as a sustainable and environmentally friendly strategy to increase persistence and productivity in turf-grasses.

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