Academic literature on the topic 'Hedgerow intercropping – Western Australia'

The biophysical performance of hedgerow intercropping for soil fertility inprovement was assessed in a farmer-participatory trial in western Kenya over three years. Farmers successfully established dense hedgerows (median 6680 trees ha−1 on plots of 790 m2, but annual yields of hedgerow prunings of Leucaena leucocephala and Calliandra calothyrsus (1–4 t ha−1), were low compared to potentials in the region (4–8 t ha−1). The hedgerows reduced slopes from 7.2 to 4.5% within alleys (p < 0.01) but had no effect on grain yield over five seasons. Little of the variation in grain yield between hedgerow plots and control plots without hedgerows (adjusted r2 = 11%) and among control plots (adjusted r2 = 29%) could be accounted for by linear regression with measured agronomic and socio-economic variables. Fully researcher-managed trials are recommended for agronomic evaluation of complex agroforestry technologies.

Hedgerow intercropping is evaluated both economically and from the farmers' viewpoint, based on four years of experience of 45 farmers in western Kenya. Farmers were able to establish and prune the hedges; however, both activities considerably increased labour use during the busiest period of the year. Women did not generally prune the hedges. The average extra maize yield required each year, beginning in the second year, to cover the added cost of hedgerow intercropping was 10.5% (s.d. 5.5) when based on returns to land and 17.5% (s.d. 6.5) based on returns to labour. Although about half the farmers claimed that hedges improved crop yields, after three years of experimentation only about one-fifth planted additional hedges and only 14% did so to improve soil fertility. It thus appears that the potential for its adoption as a soil fertility practice in this area is low. Control plots were of little use as farmers were more interested in contrasting test-plot yields with past yields than comparing the test and control plots. Different types of trials may be required to obtain reliable biophysical data on yield response and socio-economic data on farmer assessment of complex agroforestry technologies.

The environment, duplex soil types and trends in crop production in South Australia, southern New South Wales, north-eastern and north-central Victoria, the southern Wimmera and the Victorian Western District are reviewed. In the latter 2 regions, pastoral industries dominate and crop production is curtailed by regular and severe soil waterlogging, except for limited areas of lower rainfall. Subsurface drainage can eliminate waterlogging, but is feasible only for the Western District where subsoils are sufficiently stable. The other regions all have a long history of soil degradation due to cropping practices, but these effects can now be minimised with the use of direct drilling and stubble retention cropping methods. A vigorous pasture ley phase is still considered necessary to maintain nitrogen levels and to restore soil structure to adequate levels for sustainable farming. Future productivity improvements will require increased root growth in the subsoils. Deep ripping, 'slotting' of gypsum, and crop species capable of opening up subsoils are techniques which may hold promise in this regard. The inclusion of lucerne, a perennial species, in annual pastures and intercropping at intervals is a technique being pioneered in north-central and western Victoria and may provide the best opportunity to crop duplex soils successfully without associated land degradation.

Studies were undertaken across five field locations in Western Australia to determine the relative changes in disease severity and subsequent field pea yield from up to four foliar pathogens associated with a field pea foliar disease complex (viz. Didymella, Phoma, Peronospora, Septoria), across four different pea varieties sown at three different times and at three different densities. Delaying sowing of field pea significantly (P<0.05) reduced severity of Ascochyta blight (all five locations) and Septoria blight (1 location), increased severity of downy mildew (4 locations), but had no effect on seed yield. In relation to Ascochyta blight severity at 80 days after sowing, at all locations the early time of sowing had significantly (P<0.05) more severe Ascochyta blight than the mid and late times of sowing. Increasing actual plant density from 20-25 plants m-2 to 58-78 plants m-2 significantly (P<0.05) increased the severity of the Ascochyta blight (4 locations) and downy mildew (1 location), and increased seed yield at four locations irrespective of sowing date and three locations irrespective of variety. Compared with varieties Dundale, Wirrega and Pennant, variety Alma showed significantly (P<0.05) less severe Ascochyta blight (1 location), downy mildew (1 location) and Septoria blight (1 location). Grain yield was highest for the early time of sowing at three locations. Varieties Alma, Dundale and Wirrega significantly (P<0.05) out yielded Pennant at four locations. The percentage of isolations of individual Ascochyta blight pathogens at 80 days after the first time of sowing varied greatly, with Didymella ranging 25-93% and Phoma from 6- 23% across the five field locations. This fluctuating nature of individual pathogen types and proportions within the Ascochyta blight complex, along with variation in occurrence of Peronospora and Septoria, highlights the challenges to understand and manage the complexities of co-occurring different foliar pathogens of field pea. While the search for more effective host resistance continues, there is a need for and opportunities from further exploring and exploiting cultural management approaches focussing on crop sequence diversification, intercropping, manipulating time of sowing and stand density, and application of improved seed sanitation and residue/inoculum management practices. We discuss the constraints and opportunities towards overcoming the challenges associated with managing foliar disease complexes in field pea.

[Truncated abstract] Removal of native vegetation to facilitate traditional agriculture practices has been shown to reduce ecosystem health, and restricts the native habitat. The subsequent change in the predominant vegetation water use patterns has altered the catchment water balance, and hydrology which results in land degradation through such processes of salinisation and water logging. More recently, moves toward more sustainable farming practices have been taken to help re-establish catchment hydrological equilibrium and improve catchment ecosystem services. Agroforestry is one such vehicle for this reestablishment. Perennial native vegetation has been shown to have a significant effect on catchment processes, mitigating any further degradation of the land. The effect of alternating native perennial tree belts with traditional broad acre agriculture in the alleys, referred to as alley farming, is investigated in this thesis due to the potential environmental and economic benefits that can result. This thesis investigates the impact of tree belts upon the water table and aims to gauge the ability of alley farming at controlling recharge within the low-medium rainfall zone on the valley floor. The basis of this research is the analysis of data collected from the Toolibin Alley Faring Trial. This experiment was established in 1995 to assess the viability of alley farming and incorporates different combinations of belt width, alley width and revegetation density. Transects of piezometers within each design have been monitored from October 1995 to January 2008. The piezometers were sporadically monitored over this period on a total of 39 dates. ... To further understand the response observed in the water table data, in depth hydrograph analysis of the control piezometer water levels was conducted. The statistical analysis demonstrates that the belts are having a very limited impact on the water table morphology, this is associated with the restricted use of groundwater by the perennial tree belts due to the poor quality, has been applied. This explains why there is limited signature of increased water table depth in the statistical analysis; there is evidence that alley farming as a means of reducing recharge may work however the overriding control on the trial are the rainfall trends rather than perennial growth. The low perennial biomass production at the site is an effect of limited water resources; however a significant distinction can be made between the water table depth and variability beneath high and low biomass belts. There are three main controls at the site; climate, development of perennial biomass and development of perennial root systems (both vertically and laterally). The regional climatic trends will influence water table levels creating a greater soil water storage capacity; therefore the contribution of soil water to transpiration rates will enable the tree belts to have some impact on recharge. Of the alley farming designs tested, the optimal planting density and belt/alley design, from an economic perspective, is identified as having a 4m belt width which generated the greatest biomass. As a means of controlling recharge at the site the effectiveness of alley farming is limited due the shallow saline water table limiting perennial growth.

[Truncated abstract] Insufficient water use by annual crop and pasture species leading to costly rises in saline watertables has prompted research into potentially profitable deep-rooted perennial species in the Western Australian wheatbelt. Native mallee eucalypts are currently being developed as a short-rotation coppice crop for production of leaf oils, activated carbon and bio-electricity for low rainfall areas (300—450 mm) too dry for many of the traditional timber and forage species. The research in this study was aimed at developing a knowledge base necessary to grow and manage coppiced mallee eucalypts for both high productivity and salinity control. This firstly necessitated identification of suitable species, climatic and site requirements favourable to rapid growth, and understanding of factors likely to affect yield of the desirable leaf oil constituent, 1,8-cineole. This was undertaken using nine mallee taxa at twelve sites with two harvest regimes. E. kochii subsp. plenissima emerged as showing promise in the central and northern wheatbelt, particularly at a deep acid sand site (Gn 2.61; Northcote, 1979), so further studies focussed on physiology of its resprouting, water use and water-use efficiency at a similar site near Kalannie. Young E. kochii trees were well equipped with large numbers of meristematic foci and adequate root starch reserves to endure repeated shoot removal. The cutting season and interval between cuts were then demonstrated to have a strong influence on productivity, since first-year coppice growth was slow and root systems appeared to cease in secondary growth during the first 1.5—2.5 years after cutting. After decapitation, trees altered their physiology to promote rapid replacement of shoots. Compared to uncut trees, leaves of coppices were formed with a low carbon content per unit area, and showed high stomatal conductance accompanied by high leaf photosynthetic rates. Whole-plant water use efficiency of coppiced trees was unusually high due to their fast relative growth rates associated with preferential investments of photosynthates into regenerating canopies rather than roots. Despite relatively small leaf areas on coppice shoots over the two years following decapitation, high leaf transpiration rates resulted in coppices using water at rates far in excess of that falling as rain on the tree belt area. Water budgets showed that 20 % of the study paddock would have been needed as 0—2 year coppices in 5 m wide twin-row belts in order to maintain hydrological balance over the study period. Maximum water use occurred where uncut trees were accessing a fresh perched aquifer, but where this was not present water budgets still showed transpiration of uncut trees occurring at rates equivalent to 3—4 times rainfall incident on the tree belt canopy. In this scenario, only 10 % of the paddock surface would have been required under 5 m wide tree belts to restore hydrological balance, but competition losses in adjacent pasture would have been greater

"June 2001"
Bibliography: p. 165-183.
xxviii, 250 p. : ill., plates (col.), maps (col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The aims of this study were to develop models for predicting groundwater recharge from alley farming systems in the Murray Basin and for designing alley farms that will result in a prescribed recharge reduction. --p. 158.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002