Western Australian Farms Research Articles

Lessons learnt: crop-seed cleaning reduces weed-seed contamination in Western Australian grain samples

Weeds are a major contributing factor to crop yield loss. Weed control is regularly practiced during the growing season, with many growers making a conscious effort to minimise weed-seed return to the soil seedbank during the cropping program. However, growers may be unintentionally introducing weed seeds through sowing of contaminated crop seed. Using samples of crop seed obtained from 29 growers across two Western Australian grain-growing regions, 81 samples were hand-cleaned to determine weed-seed contamination levels. Of those samples, 41% were weed-free, and in the remaining 59%, the main contaminant was Lolium rigidum (annual ryegrass), occurring in 49% of contaminated samples. Crop type and cleaning method had significant effects on the level of weed-seed contamination, with barley having higher levels of contamination than other crops, and professional contractors providing lower contamination than other methods of cleaning. However, any seed-cleaning method provided significantly cleaner grain samples than no seed cleaning. This study established that crop-seed contamination was evident on Western Australian farms and that growers may be unintentionally sowing weed seeds with their crops. Seed cleaning combined with judicious paddock selection and weed-seed removal during the growing season can lead to weed-free crop seed.

Testing the Temporal Ability of Landsat Imagery and Precision Agriculture Technology to Provide High Resolution Historical Estimates of Wheat Yield at the Farm Scale

The long term archiving of both Landsat imagery and wheat yield mapping datasets sensed by precision agriculture technology has the potential through the development of statistical relationships to predict high resolution estimates of wheat yield over large areas for multiple seasons. Quantifying past yield performance over different growing seasons can inform agricultural management decisions ranging from fertilizer applications at the sub-paddock scale to changes in land use at a landscape scale. However, an understanding of the magnitude of prediction errors is needed. In this study, we examine the predictive wheat yield relationships developed from Normalised Difference Vegetation Index (NDVI) acquired Landsat imagery and combine-mounted yield monitors for three Western Australian farms over different growing seasons. We further analysed their predictive capability when these relationships are used to extrapolate yield from one farm to another. Over all seasons, the best predictions were achieved with imagery acquired in September. Of the five seasons reviewed, three showed very reasonable prediction accuracies, with the low and high rainfall years providing good predictions. Medium rainfall years showed the greatest variation in prediction accuracy with marginal to poor predictions resulting from narrow ranges of measured wheat yield and NDVI values. These results demonstrate the potential benefit of fusing together two high resolution datasets to create robust wheat yield prediction models over different growing seasons, the outputs of which can be used to inform agricultural decision making.

Determinants of the proportion of break crops on Western Australian broadacre farms

Break crops (e.g. pulses, lupins, canola, oats) underpin the continued profitability of cereal (wheat or barley) based cropping sequences. The area sown on farms to break crops varies widely across geographical regions according to climate, soil type mix, enterprise mix (crop v. livestock), and other constraints such as the prevalence of soil-borne disease. Given recent fluctuations in the area of established break crops in Western Australia, there are concerns about their long-term prospects in the farming system. A survey of the area and grain yield of break crops on-farm was combined with whole-farm bio-economic modelling to determine the upper limit to the area of break crops on representative farms in 4 agro-climatic regions. Sensitivity analysis was conducted to ascertain the potential effects of varying commodity prices (sheep and grain), costs of production, and assumptions on the yield of break crops and the boost to the yield of following cereals. The survey revealed that the two dominant break crops, lupins and canola, occupied 8–12% and 8–9%, respectively, of farm area on those farms that grew them in the medium-rainfall zone and this declined to 6–8% and 7–10% in the drier region. Nevertheless, the modelling results show that break crops are an important component of the farming system, even where the area is small, and the response of whole-farm profit to percent of the farm allocated to break crops is relatively flat near the optimum of 23–38%. The modelled area of break crops at maximum profit is higher than that found in farm surveys. The discrepancy could possibly be explained by the lower break crop yields realised by farmers and a reduced boost to cereal yields following break crops than assumed in models. Also, deterministic models do not account for risk, which is an important consideration in the decision to grow break crops. However, the yield difference does not explain the discrepancy entirely and raises questions about farmer motivations for adoption of break crops. The scope for increased area of break crops beyond 23–38% of the farm is limited, even with increases in the yield enhancements in subsequent cereal crops, higher break crop prices, and higher fertiliser costs. Further research is required to better quantify costs and benefits of break crops in Western Australian farming systems.

An Empirical Model to Estimate Achievable Adoption Potential of Annual Pasture Legumes in Western Australian Farming Systems

An Empirical Model to Estimate Achievable Adoption Potential of Annual Pasture Legumes in Western Australian Farming Systems

Exceptional circumstances provisions in Australia—is there too much emphasis on drought?

There has been a rapid evolution in drought policy over recent years. There is now much more emphasis on management capacity and preparedness building. A further step was taken in 1997 with changes to the exceptional circumstances welfare provisions to include risk factors other than drought. In this paper, the whole-farm stochastic budgeting model, RISKFARM, has been applied to New South Wales and Western Australian farming systems. The results confirm that for some farming systems, only around 10% of low net farm income years are caused by drought. Drought is just one of several factors that lead to poor financial performance. The analytical method described here provides a framework for estimating the significance of drought. The results support the use of a whole-farm approach to risk management but also indicate that the relative importance of the risk factors varies among farming regions. The likely frequency of three or four successive low net farm income years is examined and it is suggested that this could be part of the exceptional circumstances criteria. The possibility of support beyond access to welfare assistance in ‘business threatening’ situations is discussed. This suggestion should be approached from a whole-farm perspective in exceptional circumstances with limits on the frequency of access to support. Implications beyond the farm to other affected rural businesses are also discussed.

Growth, yield and neurotoxin (ODAP) concentration of three Lathyrus species in mediterranean-type environments of Western Australia

The growth, phenology, grain yield and neurotoxin (ODAP) content of Lathyrus sativus, L. cicera and L. ochrus were compared with a locally adapted field pea (Pisum sativum L.) to examine their potential as grain legumes in Western Australian farming systems. About 17 lines of each species were obtained from ICARDA, Syria, and grown at 3 agro-climatically different sites. In general, the 3 species were later flowering than field pea, especially L. cicera and L. ochrus; however, L. sativus was the last species to mature. The best Lathyrus lines produced biomass near flowering similar to field pea. At the most favourable site, grain yields were up to 1.6, 2.6 and 1.7 t/ha for L. sativus, L. cicera and L. ochrus respectively, compared with a field pea grain yield of 3.1 t/ha. There was considerable genotype and environmental variation in ODAP concentration in the seed. On average, the ODAP concentration of L. ochrus (6.58 mg/g) was about twice that of L. sativus, and L. cicera had the lowest ODAP concentration (1.31 mg/g). Given that Lathyrus spp. have not had the same breeding effort as field pea and other grain legumes in Australia, these results encourage further selection or breeding. In the shor-tseasoned, mediterranean-type environment of Western Australia, harvest indices and grain yields could be improved with early flowering. Low ODAP concentration should also be sought.

Naturalized subterranean clover (Trifolium subterraneum L.) in Western Australia: the strains, their distributions, characteistics, and possible origins

Seventy-two previously undescribed strains of subterranean clover were collected around Perth and in older Western Australian farming districts during 1960-1962. These are briefly described and their observed distributions listed. A few of them could have arisen in situ by natural crossing and mutation, but the majority appeared to have been introduced. A study of their observed distributions, together with a consideration of historical factors, suggests that many of the strains were introduced as early as the 1830's or 1840's. Because this was before the opening of the Suez Canal, it seems likely that they originated in England, Portugal, Madeira, or the Canary Islands, rather than throughout the Mediterranean as has been previously suggested. The commoner strains showed distinct patterns of colonization in one area, followed by varying amounts of spread along transport routes, probably by stock as undigested seeds. Indirect evidence suggested, however, that this mode of transport could not have accounted for the original transport of strains from the coast to inland areas, where many of them appear first to have become established. It is concluded that most of these must have been carried inland directly in imported hay or similar materials.