Project Report
Project Title: / Alternative Mulch Effects Upon Blueberry Root Health & Nutrient Management BMP’s / Project #: / A0576Recipient: / BC Blueberry Council
Reporting Title: / Phase 2 – Annual Report
Reporting Period: / Sept 24, 2008 to Sept 30, 2009
TRANSMITTAL NOTICE:
“I ______certify that the information contained in this report is accurate and that this project is being carried out/has been carried out in compliance with the terms of the Contribution Agreement and its Schedules. If this is a Final Report, I certify that the project is complete and that a full accounting of project revenues and expenses is enclosed. I certify that I am authorized to represent and sign on behalf of the organization.
Recipient’s Designated Officer: / Will Van Baalen(Signature) / (Printed Name) / (Date)
FOR THE FINAL REPORT ONLY:
Director of the Recipient:(Signature) / (Printed Name) / (Date)
Director of the Recipient:
(Signature) / (Printed Name) / (Date)
Executive Summary:
Interim Progress Report to BCBC & IAF
Period Ending: September 30th 2009
Prepared by Tom Forge (AAFC), Wayne Temple (UBC) and Art Bomke (UBC)
Problem or Opportunity
Mulches are known to have profound influences on the distribution and overall biomass of blueberry root systems (Spiers 2000; Clark and Moore 1991; Patten et al. 1988; Spiers 1986). In BC and most other major blueberry-growing regions, blueberry is typically mulched with sawdust from softwood species such as Douglas-fir, pine and hemlock. Recent increases in demand for sawdust, coupled with variable sawmill activity in the Lower Mainland, have led to
increased prices and reduced availability of fir-hemlock-pine sawdust. Little is known of how blueberry responds to alternative mulch materials, such as municipal yard trimmings compost (YTC) waste, cedar sawdust, cereal straw and paper recycling wastes.
In conjunction with alternative crop mulches of benefit to growth, weed control and/or reduced incidences of root-borne diseases, we will investigate the interactive effects of different mulch types on available soil nutrients. Unlike sawdust, compost is a slow-release or neutral source of plant nutrients in addition to altering the soil microclimate; and, it could double as a replacement for both sawdust and fertilizer. Furthermore, the most recent Fraser Valley Soil Nutrient Survey (Kowalenko, Schmidt and Hughes-Games, 2007) shows that many soils under blueberry production are well supplied with N, P and K. To reduce environmental risks associated with such soil nutrient loads, there is a need to reduce external and expensive fertilizer inputs; and/or define beneficial management practices (BMPs) for nutrients.
The desired outcome of this project is to provide practical information to BC blueberry growers regarding the benefits of various sustainable alternatives to sawdust for mulching. This information will enable growers to adopt alternative mulches without fear of crop failure from changes in disease pressure or altered nutrient availability. Additionally, by focussing on locally available “waste” materials, we will create opportunities for local recycling of nutrients and thereby reduce overall nutrient load on the bioregion.
Description of the Project Objectives
Sawdust mulches in blueberry production have been a traditional BMP. However, sawdust has now become a commodity that is in much demand for other purposes and hence its availability and/or expense are limiting its use in blueberry production. In addition, the high carbon-to-nitrogen ratio of sawdust fosters microbial immobilization of nitrogen in the root zone and necessitates application of synthetic fertilizers at rates in excess of actual crop requirements. YTC may be an effective alternative to sawdust as mulch for blueberry. It is a source of organic nitrogen and may help to control weeds, improve soil surface structure, conserve soil water and nutrients, and provide other soil biological benefits.
Objectives of Project I (Research/Stewardship component): Compare the effects of different types of sawdust (fir, pine, and cedar), composts and cereal straw-based mulches, and variable N fertilizer inputs with respect to:
- Overall crop performance, root distribution and biomass, root diseases and soil physical properties that influence root health,
Objectives of Project II (Research/Stewardship component): Compare the effects of different types of sawdust (fir, pine, and cedar), composts and cereal straw-based mulches, and variable N fertilizer inputs with respect to:
- Monitoring and assessing spring and fall levels of soil available N to improve understanding of how mulches may help to conserve soil N, reduce fertilizer costs/inputs and fall residual N levels.
Objectives of Project III ( BMPs Awareness & Education component): To participate and communicate in regional discussions regarding producers’ potential alternatives to soil mulching BMPs in context with respect to benefits to crop growth and development and reduced incidences of plant diseases/pathogens; and, “Soil Nutrient Management” BMPs targeted at producer awareness and education activities regarding reduced fertilizer inputs.
Key Activities & Progress to Date
Project I & II: YTC as Soil Surface Mulch in Blueberry Production
Key Activities: Dr. Forge (Agriculture and Agri-Food Canada (AAFC) – Agassiz) is currently monitoring and evaluating the City of Vancouver YTC as soil surface mulch in blueberry production – situated on a sandy loam soil - at the Abbotsford, BC Research Station. He is also providing expertise, field and laboratory assistance for more recently established experiments including a replicated on-farm experiment on heavy-textured soils of Delta, and a third experiment at UBC.
Pacific Agri-Food Research Centre experiment 1 (Forge): This field experiment was established in spring of 2006 at the AAFC Clearbrook substation, using AAFC resources. The objective is to compare fir sawdust mulch (industry standard; check treatment) to mulch of yard trimmings compost from the City of Vancouver, in fumigated and non-fumigated soil. Each mulch treatment plot is split into two subplots of ‘Duke’ and ‘Reka’. Additional treatments include sulphur-amended (acidified) compost, compost with half the fertilizer N applied to the check, and compost with the same fertilizer N as the check. The experimental site is naturally infested with root-lesion nematodes (Pratylenchus penetrans). Phytophthora cinnamomi and Pythium sylvaticum have been recovered from the rhizosphere of raspberry at the site (based on preliminary research in 2007) and are expected to influence blueberry root health at the site.
2009 was the second year that yields were measured in these plots. Berries were picked twice from the two central plants in each subplot. Fumigation increased yields, with average yields of 11.2 and 9.4 kg berries/plant for fumigated and non-fumigated plots, respectively. The pathogen or pathogen complex responsible for this suppression of yield in non-fumigated soil is not fully known at this point. The site is naturally infested with root-lesion nematodes (Pratylenchus penetrans), and as of August 2009 the fumigated rows were still free of root-lesion nematodes. The pathogenicity of root-lesion nematodes is unclear, however, and is currently under investigation (see below). In 2008, two adjacent plants of ‘Reka’ in a fumigated, compost amended plot died of apparent root-rot. Plating and PCR analyses of root tissue from these plants revealed the presence of Pythium sylvaticum but not Phytophthora cinnamomi. The pathogenicity of P. sylvaticum to blueberry is currently not known and is under investigation by Siva Sabaratnam (BCMAL).
There were also statistically significant differences between cultivars, with ‘Duke’ and ‘Reka’ yielding, respectively, 11.2 and 9.3 kg berries/plant. Mulch treatment effects were not statistically significant, but there has been a strong tendency for yields in compost plots to increase with supplemental N, suggesting that compost mulch alone does not supply adequate N for optimal yields; average yields are presented in the following figure:
Pacific Agri-Food Research Centre experiment 2 (Forge): This field experiment was established in spring of 2007 on a new planting of ‘Chippewa’. The objective was to compare the industry standard of a combination of fir sawdust mulch and ammonium sulphate fertilizer (Fert/SD) to mulches of sawdust with broiler manure as N source (BM/SD), sawdust with poultry manure compost as N source (PARC/SD), poultry manure compost mulch (PARC), municipal biosolids compost mulch (Kent), and shredded paper mulch with broiler manure as N source (BM/SP). Where broiler manure and PARC compost were applied as N sources, application rates were targeted to provide the same amount of potentially available N as the fertilizer applied to the control, and the high-N materials was applied as a band on top of the sawdust or paper mulch. Where PARC and Kent composts were applied as mulches, they were applied to a depth of approximately 5 cm; sawdust mulches were applied to a similar depth.
Plants were grown through 2008 and the experiment was terminated in winter of 2009. Four senescent plants were removed from the centre of each plot, air-dried, and stem and root weights were determined. There was a highly significant effect of mulch treatment on plant growth. Plants grown in mulches of PARC compost or shredded paper (with broiler manure as N source) grew very little. Plants grown with Kent compost mulch had moderate growth. There are several possible reasons for the poor growth of plants grown with mulches of compost or shredded paper. We speculate that high pH and high EC resulting from those mulches were responsible for the poor growth, as the pH of these materials is greater than 7 (data not shown) and earlier work at this site demonstrated that shredded paper mulch increases soil pH (Forge et al. 2009). This experiment demonstrated that it may be feasible to use broiler manure or a high-N compost, such as PARC, as alternative sources of N if they are layered over sawdust. The use of PARC compost as an alternative organic source of N is continuing to be evaluated as part of another experiment located at the AAFC-Agassiz research centre.
On-Farm Experiment: The third experiment will was established in a grower’s field (Ken Bates, Delta) in late summer 2008. Treatments include (1) fir sawdust, (2) yard trimmings compost (YTC), (3) a 50:50 layer mixture of YTC over top of Sawdust, (4) a 50:50 layer mixture of sawdust over YTC, and (5) chopped barley straw. There are five replicate plots of each treatment arranged in a randomized complete block design. Each whole-plot treatment is
divided into three sub-plots with N fertilizer treatments applied to the row band width: (1) no extra N, (2) 1st fertilizer application only (May 16, 2009 - 275 kg/ha of 14-6-2 + 1.2Mg + 0.4 Fe) or approximately half the recommended N input, and (3) 1st & 2nd fertilizer application (May 16, 2009 - 275 kg/ha of 14-6-2 + 1.2Mg + 0.4Fe; and, June 15, 2009 - 275 kg/ha 14-0-4 + 22 S +2Mg + 0.2B + 2Ca) which were the fertilizer supplier recommended inputs.
Nutrient analyses:Soil samples have/will be taken for analyses of available N in May (at the time of first fertilizer application), late August (after harvest) and/or October (before onset of high rainfall and leaching). Late August 2009 sampling was not possible because the soil was too hard. In order to provide comparable data, the sampling strategy will be similar that used in the Fraser Valley Soil Nutrient Survey, and will involve taking cores from 0-30 and 30-60 cm (October sample date only) depth intervals, from the fertilizer band/herbicide strip area under the blueberry canopy. In addition, leaf samples have been taken in August for tissue testing analyzes (eg. N, P, K, Ca, Mg, Na, Fe, Cu, Mn, Zn and B).
The table and photos below show that the YTC had much more weeds associated with this mulch in the early spring. Few weed were associated with sawdust, sawdust over YTC and barley straw mulch treatments, with the chopped barley straw having the best weed control.
Sawdust over YTC Mulch – Few WeedsYTC Compost Mulch – Lots of Weeds
Barley Straw Mulch – Few WeedsSawdust Mulch – Few Weeds
The Delta site September 2008 soil sample analysis – see table below – indicated a residual N concentration of 55 mg/kg or approximately some 150 kg/ha (0 to 30 depth; bulk density of 860 kg/m3); P concentration of 222 mg/kg and K concentration of 230 mg/kg. These NPK concentrations are consistent with those observed in the 2005 Nutrient Survey performed by the BCMAF; and are considered high or excessive. Fertilizer P and K inputs are not necessary. Soil Cu and B levels appear low and perhaps warrant future applications. Applications of Ca and Mg also appear not necessary. The soil pH and available Fe levels also appear to be optimal and inputs appear not warranted.
Leaf tissue samples – taken on August 12, 2009 - are currently being analyzed and should help demonstrate any deficiencies/excesses subject to the fertilizer treatment inputs described above.
Soil Available N and K Levels at1stFertilizer Application - May 21, 2009
At the time of 1st fertilizer application none of the mulch treatments had any significant effect (p<0.05) on soil pH, %C, %N, available P, Ca, Mg, Na, Fe, Cu, Mn, Zn and B. The YTC mulches – including those with the sawdust layer - did significantly elevate EC levels (p=0.03; data not presented). The YTC compost mulches appear to be providing the soil with approximately 50 kg/ha available N and 225 mg/kgavailable K at the time of the first fertilizer application – see graphs above. Both of the YTC and sawdust 50:50 layer mulches also provided about 25 kg/ha soil available N, which is about half that which was provided by the straight YTC mulch. The amounts of NH4-N were low – approximately 7 kg/ha – with no significant mulch effects, hence much of the significant available N was NO3-N. In terms of N management the amounts of NH4-N levels are low and this perhaps warrants NH4-N fertilizer source applications provided that such a form of available N is in fact reaching the soil and not immediately converting to NO3-N in the mulch and/or soil.
With the sawdust and YTC 50:50 layered mulches, only the mulch treatment which had the YTC on the bottom had elevated K levels in the soil. This suggests the YTC/sawdust layer mulch with the sawdust on the bottom prevented much of K leaching into the soil below. In terms of fertilizer management this also suggests the YTC is providing much K; and, that the sawdust may reduce fertilizer K inputs from reaching the soil root zone.
Four granular-matrix ‘Watermark’ soil moisture probes were installed in a compost plot, barley straw plot, and two sawdust plots. The probes were installed at 10 to 15 cm depth in the centre of the blueberry bed. Traces of average water potentials are plotted below (greater values represent drier soil). Soil under the compost mulch tended to stay moister than under the sawdust mulch.
UBC Farm Experiment
The fourth experiment has beenestablished at the UBC Farm. The site itself is approximately 0.4ha and is being managed according to organic farming practices. There are 17 rows (15 experiment rows with two outside guard rows), each approximately 40m in length. The15 experiment rows (3 treatments x 5 blocks) compares the effectiveness of yard trimmings compost and/or sawdust as rooting mulches to that of no mulch or just soil. Each of the mulch treatments will be evaluated with the use of sawdust, yard trimmings compost with the black plastic landscape material. Each of the 3 mulch treatment will in-turn have four subplot treatments – applied in spring 2010 - of organic fertilizer inputs, which could include no fertilizer input; fishmeal; feathermeal; and composted poultry litter. A “mow and blow” fertility input treatment may be included using one of the blocks and is subject to further evaluation subsequent to inter-row cover crop plant establishment. The plants are spaced 1.2m apart with 1.5m wide rows; and, the alleyways are approximately 1.5m wide.
Nutrition:The high soil OM levels at the UBC site (≈ 12.7% - see table below) did not warrant any pre-mulch soil amendments.
The soil (<2.00mm) consisted of 70% very coarse sand; 21% fine silt and 9% fine clay. The UBC Farm soil is very high in available P and has adequate K levels. Soil Mg, Fe, Cu and B levels may be on the low side and warrant future tissue testing/evaluation. At the time of planting the soil pH was 5.6–perhaps a little on the high side. However, the soil is a Fe-rich Podzol and hopefully Fe availability will not become an issue in the future – future leaf tissue analysis will determine this.
Establishment:In terms of establishing this “organic” site, several soil and weed issues presented some difficult challenges. The most challenging aspect of the site is its sheer volume of rocks. Approximately 50% of the soil volume isgreater than 2.00mm, with a good proportion consisting of rocks – most ranging from fist size to boulders 20to 30 cm in diameter. In terms of site preparation this necessitated that the mounded rows be raked clean of such large rocks prior to planting in order to provide a soil with adequate soil rooting volume and water retention. Once planted 12mmdouble line irrigation (37 cm emitter spacing) system was installed in mid-May. Lines were eventually spaced 40 cm apart.
Weed Control:Shortly after planting, a good portion of the field became infested with couch grass and many other annual weeds – see Table below; no fewer than 23 species. This necessitated a strategy to control the weeds and eradicate the grass to prevent its proliferation into the planted blueberry root masses. Furthermore, applications of organic mulch(sawdust and YTC) and seeding of the alleyways were not possible until the couch grass was eliminated. In establishing the field using “organic” conventions, it has become clear that the use of the black plastic landscape fabric is essential for weed control.To control the couch grass infestation black plastic fabric was applied in the early spring to each of the rows; and, the alleyways were continuously cultivated to a depth of 30cm over the course of the spring and much of the summer. Many more rocks were also picked. This strategy did eliminate the couch grass come mid-August, at which time, the sawdust and YTC mulches were applied over the rows to a depth of 10cm; and, with the plastic mulch re-applied over all rows.