Literatura científica selecionada sobre o tema "Crop yields South Australia Case studies"

Nitrogen balances of narrow leaf lupin (Lupinus angustifolius L.), albus lupin (L. albus L.), field pea (Pisum sativum L.), chickpea (Cicer arietinum L.), and barley (Hordeum vulgare L.) sown over a range of dates were examined in 1992 in a rotation study at Wagga Wagga, NSW. Each N budget included assessment of dependence on fixed as opposed to soil N, peak aboveground biomass N, and N removed as grain or returned as unharvested aboveground crop residues. N balances of wheat sown across the plots in 1993 were assessed similarly in terms of biomass and grain yield. Yields, N2 fixation, and crop residue N balances of the legumes were markedly influenced by sowing time, and superior performance of lupins over other species was related to higher biomass production and proportional dependence on N2 fixation, together with a poorer harvest index. Residual N balances in aboveground biomass after harvest of the 1992 crops were significantly correlated with soil mineral N at 1993 sowing and with biomass and grain N yields of the resulting wheat crop. Best mean fixation and grain N yield came from albus lupin. Wheat grain N yields following the 2 lupins were some 20% greater than after fiield pea and chickpea and 3 times greater than after barley. Net soil N balance based solely on aboveground returns of N of legumes in 1992 through to harvest of wheat in 1993 was least for narrow leaf lupin-wheat ( –20 kg N/ha), followed by albus lupin-wheat ( –44), chickpea-wheat ( –74), and field pea-wheat ( –96). Corresponding combined grain N yields (legume+wheat) from the 4 rotations were 269, 361, 178, and 229 kg N/ha, respectively. The barley-wheat rotation yielded a similarly computed soil N deficit of 67 kg/ha. Data are discussed in relation to other studies on legume-based rotations.

The development of recommendations for drying-off management in sugarcane is difficult due to climatic variability and lack of knowledge of the sensitivity of changes in sucrose content and cane yield to severity of water deficit. Relative cane biomass targets were developed for drying-off irrigated sugarcane before harvest based on derived relationships between cane yield, cane dry weight, and sucrose concentration, using pooled data from previous field studies. These targets were then linked to a crop–soil model and long-term climate data to determine the economically optimum duration of drying-off, and its variability from season to season for 2 locations in Australia and one location in South Africa, for a range of harvest dates and soil types. The crop–soil model was validated on yields measured in 37 drying-off treatments conducted in South Africa and Australia. The simulation results show that the required drying-off duration can be highly variable, although the level of variability is not necessarily correlated with rainfall per se. There were interactions between soil type and harvest date, but not at every location. The systems approach outlined here can be useful in developing recommendations for drying-off where experience is limited, such as in expanding areas of sugar industries, for districts in which the practice of irrigation is increasing, or for harvest dates outside the current harvesting season.

The multiple factors constraining the growth, reproduction, and survival of diverse organisms are often non-additive. Research of interacting factors generally involves conceptual models that are specific for target organism, type of stress, and process. As a complement to this reductionist, bottom-up view, in this review I discuss a quantitative top-down approach to interacting stresses based on co-limitation theory. Firstly, co-limitation theory is revised. Co-limitation is operationally identified when the output response of a biological system (e.g. plant or population growth) to two or more inputs is greater than its response to each factor in isolation. The hypothesis of Bloom, Chapin, and Mooney, that plant growth is maximised when it is equally limited by all resources, is reworded in terms of co-limitation and formulated in quantitative terms, i.e. for a given intensity of aggregate stress, plant growth is proportional to degree of resource co-limitation. Emphasis is placed on the problems associated with the quantification of co-limitation. It is proposed that seasonal indices of nitrogen and water stress calculated with crop simulation models can be integrated in indices accounting for the aggregated intensity of water and nitrogen stress (SWN), the degree of water and nitrogen co-limitation (CWN), and the integrated effect of stress and co-limitation (SCWN = CWN/SWN). The expectation is that plant growth and yield should be an inverse function of stress intensity and a direct function of co-limitation, thus proportional to SCWN. Secondly, the constraints imposed by water and nitrogen availability on yield and water use efficiency of wheat crops are highlighted in case studies of low-input farming systems of south-eastern Australia. Thirdly, the concept of co-limitation is applied to the analysis of (i) grain yield responses to water–nitrogen interactions, and (ii) trade-offs between nitrogen- and water-use efficiency. In agreement with theoretical expectations, measured grain yield is found to be proportional to modelled SCWN. Productivity gains associated with intensification of cropping practices are interpreted in terms of a trade-off, whereby water-use efficiency is improved at the expense of nitrogen-use efficiency, thus leading to a higher degree of resource co-limitation.

Phoma macdonaldii Boerma is the pathogen of sunflower black stem disease, causing dark black, oval to long lesions on stems of sunflower plants. Infection during early growth stages can reduce yield by 10 to 30% (3). This fungal disease is distributed mainly in North and South America and Europe. In China, the first case was reported in Xinjiang in 2008 (1), and was believed to be introduced as a result of hybrid sunflower seeds being imported from abroad. The Chinese government included this fungus into its quarantine pests list in 2010 (2). Since China imports a great number of sunflower seeds to grow in its Northern provinces from epidemic areas such as the United States, Argentina, and France, monitoring the disease occurrence in planting areas became crucial. During 2010 and 2011 growing seasons, surveys were conducted in 37 commercial farms or individual households in 12 counties of five areas (Xinjiang, Inner Mongolia, Ningxia, Hebei, and Beijing). A total of 185 suspicious samples of sunflower black stem disease were collected and all were found from imported hybrid seed fields. The presence of P. macdonaldii was confirmed as following: 4 mm2 tissue pieces cut from lesion margins were disinfected with 1% NaOCl, plated on APDA (acid potato dextrose agar, 4.5 to 5.0 pH adjusted with lactic acid), and incubated at 25°C with 12L:12D photoperiod. After 3 days of incubation, colonies were opalescent or ivory in color, and fluffy or flocculent in appearance. After 4 to 6 days, a large number of spherical or oblate black-brown pycnidia were formed separately or in clusters with thin wall and papillate ostiole in diameter of 135 to 324 μm (average 178 μm). A light pink or opalescent gelatinous substance (pycnidiospores) exuded from the ostiole. Pycnidiospores were single celled, oval or kidney-shaped and hyaline both with and without oil balls, and 1.5 to 3.0 μm × 3.0 to 6.5 μm (average 2.0 × 4.7 μm). Sequences of ITS1-5.8S- ITS2 rDNA fragment of all isolates (GenBank Accession No. JQ979487, JQ979488) were identical and had 100% homology with P. macdonaldii isolates from Xinjiang (HM003206) and Australia (DQ351823, DQ351825) and 99% homology with isolates from the former Yugoslavia (DQ351821, DQ351822) in GenBank. Pathogenicity studies of the isolate were performed by injecting 10 × 106/ml spore suspension into the hypocotyl of four true leaves of sunflower seedlings with a syringe. Sterile water was injected as control. After being inoculated in a plastic bag in the shade at room temperature for 48 h, the plastic bag was removed and the seedlings were grown under natural light. Symptoms of black stem disease were observed in all P. macdonaldii inoculated seedlings and the fungus was reisolated from the lesions for confirmation. The current survey found that 105 of 185 suspicious samples were P. macdonaldii positive and were all from four counties in Xinjiang, suggesting that the disease has not spread to other areas since its introduction. The monitoring of sunflower black stem disease is continuing, as is the research for measuring P. macdonaldii adaptability in China and the development of rapid molecular detection technology. References: (1) W. M. Chen et al. J. Yunnan Agric. Univ. 23:609, 2008. (2) J. Luo et al. Australas. Plant Pathol. 40:504, 2011. (3) E. Miric et al. Aust. J. Agr. Res. 50:325, 1999.

AbstractNo-till practices have improved crop yields in the semiarid Great Plains. However, a recent assessment of research studies across the globe indicated that crop yields are often reduced by no-till. To understand this contrast, we examined corn yields across time in a no-till cropping system of one producer in central South Dakota to identify factors associated with increased yield. The producer started no-till in 1990; by 2013, corn yield increased 116%. In comparison, corn increased only 32% during this interval with a conventional, tillage-based system in a neighboring county. With no-till, corn yields increased in increments due to changes in management. For example, corn yield increased 52% when crop diversity in the rotation was expanded from 2 to 5 crops. A further 18% gain in yield occurred when dry pea was grown before corn in sequence. Nitrogen (N) requirement for corn is 25% lower in no-till compared with a tillage-based rotation. Furthermore, phosphorus (P) fertilizer input also has been reduced 30% after 20 yr of no-till, even with higher yields. Our case study shows that integrating no-till with crop diversity and soil microbial changes improves corn yield considerably. This integration also reduces need for inputs such as water, N and P.

The extraction of soil water by dryland crops and pastures in south-eastern Australia was examined in 3 studies. The first was a review of 13 published measurements of soil water-use under wheat at several locations in southern New South Wales. Of these, 8 showed significantly more water extracted by crops managed with increased nitrogen supply or growing after a break crop. The mean additional soil water extraction in response to break crops was 31 mm and to additional N was 11 mm. The second study used the SIMTAG model to simulate growth and water-use by wheat in relation to crop management at Wagga Wagga. The model was set up to simulate crops that produced either average district yields or the potential yields achievable with good management. When simulated over 50 years of weather data, the combined water loss as drainage and runoff was predicted to be 67 mm/year for poorly managed crops and 37 mm for well-managed crops. Water outflow was concentrated in 70% of years for the poorly managed crops and 56% for the well-managed crops. In those years the mean losses were estimated to be 95 mm and 66 mm, respectively. The third study reports soil water measured twice each year during a phased pasture–crop sequence over 6.5 years at Junee. Mean water content of the top 2.0 m of soil under a lucerne pasture averaged 211 mm less than under a subterranean clover-based annual pasture and 101 mm less than under well-managed crops. Collectively, these results suggest that lucerne pastures and improved crop management can result in greater use of rainfall than the previous farming systems based on annual pastures, fallows, and poorly managed crops. The tactical use of lucerne-based pastures in sequence with well-managed crops can help the dewatering of the soil andreduce or eliminate the risk of groundwater recharge.

California is the second largest sweet cherry producer in the United States with annual revenues up to $200 million. The South Australian cherry industry generates about 10% of Australia's overall production with approximately 1,500 metric tons of cherries produced yearly. In California, perennial canker diseases and subsequent branch dieback are responsible for extensive damage throughout sweet cherry orchards, reducing annual yields and tree longevity. Surveys of cherry orchards and isolation work were conducted in California to identify the main canker-causing agents. Calosphaeria pulchella was the main fungus isolated from cankers, followed by Eutypa lata and Leucostoma persoonii, respectively. Preliminary surveys in cherry orchards in South Australia documented C. pulchella and L. persoonii in cankers. The pathogenicity of C. pulchella in sweet cherry was confirmed following field inoculations of 2- to 3-year-old branches. C. pulchella was able to infect healthy wood and produce cankers with as much virulence as E. lata or L. persoonii. Spore trapping studies were conducted in two sweet cherry orchards in California to investigate the seasonal abundance of C. pulchella spores. Experiments showed that rain and sprinkler irrigation were important factors for aerial dissemination. Finally, this study illustrates the symptoms and signs of the new disease Calosphaeria canker.

The seasonal pattern of pasture production and its variability from year to year are important for pasture-based livestock production systems in south-eastern Australia because they influence key strategic decisions such as stocking rate and timing of the reproductive cycle. In this study, the effects of observed climate variations over the period 1960–2015 on pasture growth patterns were investigated by using a biophysical modelling approach. Pasture growth rates were simulated using DairyMod biophysical software at five sites ranging from high-rainfall, cool temperate at Elliott in Tasmania to medium-rainfall, warm temperate at Wagga Wagga in southern New South Wales. Annual pasture yields showed a small increasing rate of 50 kg DM/ha.year at Elliott and 40 kg DM/ha.year at Ellinbank (P < 0.05), whereas other sites showed no significant trend over time. A cross-site analysis of seasonal average pasture growth rates predicted under four different discrete periods of 14 years each showed that winter growth has increased steadily through time (P = 0.001), and spring pasture growth rate has decreased (P < 0.001) in 2002–15 compared with the earlier periods. Year-to-year pasture yield variability (coefficient of variation) during autumn and spring seasons has also increased (P < 0.05) across sites in the period 2002–15 compared with 1998–2001. At each site, the number of spring days with water stress (growth limiting factor_water <0.7) was ~10 times greater than the number of days with temperature stress (growth limiting factor_temperature <0.7). There was an increase in the number of days with water stress at Wagga Wagga, and increased heat stress at Wagga Wagga and Hamilton (P < 0.05) in the most recent period. These results highlight the importance of incorporating more heat-tolerant and deep-rooting cultivars into pasture-based production system. Although previous studies of climate-change impact have predicted increasing winter growth rates and a contraction of the spring growing season in the future (2030), this study provides clear evidence that these changes are already occurring under the observed climate in south-eastern Australia.

Forage cereals offer the potential to increase the amount of forage grown and consumed on dairy farms in southern Australia. The effect of single or multiple grazing of winter cereal forages by lactating dairy cattle on dry matter (DM) yield and nutritive value at grazing and on subsequent silage production harvested at the soft-dough stage of growth was determined in three studies in south-western Victoria. In the first two studies, a range of forage cereals and an annual ryegrass were grazed either once (G1) during tillering (GS 21–29), followed by locking up for silage, grazed twice (G2) (GS 21–29 and GS 32–34), followed by locking up for silage, or not grazed (NG) and harvested for silage only. In the third study, two forage cereals were either ungrazed (NG) or grazed at either GS 21, GS 24, GS 30 or GS 32 and subsequently locked up and harvested for silage. All silage harvests occurred at GS 84 (soft dough). In all studies, grazing at early tillering resulted in DM yield of less than 1.4 t DM/ha, although crude protein (CP) (30–37% DM) and estimated metabolisable energy (ME) (12.2–14 MJ/kg DM) were high. Deferring grazing until the start of stem elongation resulted in higher DM yields (1.8–4.3 t DM/ha). Silage DM yields were higher (P < 0.05) for G1 and NG treatments than for G2 in all cases apart from McKellar wheat in study 1. At silage harvest, CP and estimated ME contents of cereals were lower than for annual ryegrass. In general, total DM yields across the growing season were higher for the G1 and NG treatments compared with forages that were grazed twice before silage harvest. Deferment of a single grazing from early tillering to stem elongation did not adversely affect total DM production. However, delaying grazing until stem elongation resulted in significant declines in CP concentration and estimated ME. These studies highlight the potential of cereal forages to contribute to DM production on dairy farms in southern Australia. They can provide additional flexibility into forage systems through the provision of forage for a single grazing in early winter and in the production of high DM yield silage harvests. Cereals grazed in early winter have a high estimated ME and CP content, whereas the nutritive characteristics when harvested for silage at soft dough are of only moderate feed value. Consideration is required as to how best to incorporate these into diets of lactating dairy cattle.

Sandplain soils on the south coast of Western Australia have multiple limitations to crop production that include water repellence, low water and nutrient retention, subsoil acidity, and high soil strength. Crops on sandplain soils achieve, on average, almost 85% of their rainfall-limited yield potential; however, where there are multiple limitations the corresponding value is often <50% in any given year. Previous research has shown the value of applying clay-rich subsoil (‘claying’) to ameliorate water repellent soils and improve nutrient retention. Other studies have shown that deep ripping is effective in reducing compaction in sandplain soils. This paper quantifies the effects of 5 subsoil clay rates (0, 50, 100, 200, and 300 t/ha), with and without deep ripping to 0.5m, on soil properties, crop growth, and profitability in a replicated field experiment. Crop yields were increased by 0.3–0.6 t/ha as result of added clay. The clay content of the surface soil required to alleviate water repellence and achieve the highest yield increases was 3–6% in soils with ~1% organic carbon. Longer term effects of claying included increased soil organic carbon by 0.2%, pH by 0.6 units, potassium by 47 mg/kg, soil strength by 250 kPa, and cation exchange capacity by 1.3 cmolc/kg to a depth of 0.1 m. However, changes in plant-available water (mm/m) were inconsistent between the clay treatments. Deep ripping to 0.5 m increased crop yields by 0.1–0.5 t/ha. These crop yield responses were still evident 3 years after the ripping treatment had been applied. Soil strength measurements indicate that re-compaction of the ripped treatments had occurred to a depth of 0.2 m in the second year following ripping. Crop responses to claying and deep ripping were additive. Claying and deep ripping, while almost doubling yields, achieved only 50–70% of the rainfall-limited yield potential on these marginally fertile soils. The highest clay rates (>3–6%) had cumulative discounted cash returns $AU100–200/ha higher than the unclayed ‘control’ treatment and $300/ha higher than the lowest clay rates. For most of the clay treatments, deep ripping increased discounted returns between 2005 and 2007 by $80–120/ha.