Denise Neilsen

Influence of organic waste amendments on selected soil physical and chemical properties

Sandy, infertile soils can benefit from the addition of organic waste amendments. Annual applications of organic wastes for as long as 4 yr increased soil organic matter content, decreased soil bulk density, and increased soil water retention of a coarse-textured soil. However, soil water-holding capacity was not necessarily increased, and there was a limited effect on soil cation exchange capacity. Key words: Cation exchange capacity, water retention, soil pH, soil organic matter, soil bulk density

Effects of organic mulches on soil microfauna in the root zone of apple: implications for nutrient fluxes and functional diversity of the soil food web

A variety of organic materials (e.g. composts, paper recycling wastes, hay) can be used as in-row mulches in perennial horticultural cropping systems such as high density apple orchards. As organic materials with variable properties, such mulches can be expected to have variable effects on structure of the soil food web and mineralisation of N and P in the root zone. The overall objectives of this study were to: (1) assess the effects of a selection of organic mulches on the abundance of protozoa and nematode trophic groups; (2) use the model of Hunt et al. [Biol. Fertil. Soils 3 (1987) 393] to assess the implications of changes in microfaunal abundance for microbial turnover and N mineralisation; and (3) determine effects of the mulches on nematode indicators of increased microbial production/turnover and functional diversity of the soil food web. Organic mulch treatments commenced in 1994 and included shredded office paper, municipal biosolids, shredded paper applied over municipal biosolids, shredded paper applied over municipal compost, alfalfa hay, and black polyethylene fabric. The control was conventional tree-row weed management with glyphosate. Biosolids and municipal compost treatments were re-applied in 1997. Protozoan abundance was determined in 1998, 1999 and 2000. Nematode community structure was assessed in 1998, 1999, and twice in 2000. Nematode community parameters evaluated included: abundance of bacterivorous, fungivorous, omnivorous and predacious nematodes; abundance of the root-lesion nematode, Pratylenchus penetrans; absolute and relative abundances of enrichment opportunist nematodes (Rhabditidae+Diplogasteridae+Panagrolaimidae); Simpson’s diversity; evenness; and the indices of nematode community enrichment (EI) and structure (SI) described by Ferris et al. [Appl. Soil Ecol. 18 (2001) 13]. Measurements of the abundance of enrichment opportunists and the EI were evaluated as indicators of enhanced nutrient fluxes. Diversity and the SI were evaluated as indicators of changes in functional diversity of the soil food web. The abundance of protozoa and bacterivorous nematodes, and estimated fluxes of N and P through the microfauna, were greater under all combinations of biosolids or municipal compost and shredded paper than under the control and plastic mulch. The abundance of enrichment opportunist nematodes and the EI were also consistently greater under combinations of biosolids or municipal compost and shredded paper. The abundance of enrichment opportunists and EI were both also correlated with leaf P, providing additional evidence to support the use of these parameters as indicators of enhanced turnover of microbial biomass and nutrients. The SI was greatest under shredded paper and shredded paper applied over municipal compost, and least under municipal biosolids and alfalfa hay. Population densities of P. penetrans were reduced under shredded paper mulch relative to the control and biosolids alone.

Surface application of mulches and biosolids affect orchard soil properties after 7 years

Changes in selected soil chemical and physical properties of a coarse-textured orchard soil were measured 7 yr after establishing different orchard soil management strategies which were deemed to be environmentally sound in a high-density apple orchard. Several locally available mulches and organic wastes applied to the soil surface were maintained and assessed as to their effect on tree performance and soil properties relative to a standard commercial practice involving maintenance of a weed-free herbicide strip (known as the “check” practice). The soil chemical status of these sandy soils was readily altered when large amounts of nutrients were contained in applied mulches and biosolids. Thus, elevated soil C [and cation exchange capacity (CEC)], N, P, Zn, Fe, Mn and Cu occurred after cumulative application of 90 t ha-1 of biosolids; soil pH and Ca content increased beneath a high-Ca shredded paper mulch, and soil was enriched in P and K beneath a high-PK alfalfa mulch. Small but statistically significa...

Evaluation of organic wastes as soil amendments for cultivation of carrot and chard on irrigated sandy soils

A field trial was designed to test the potential of various wastes as soil amendments in horticultural production. Swiss chard (Beta vulgaris L.) and carrot (Daucas carota L.) were grown during 1993–1995 under irrigation in a coarse-textured, British Columbia soil to which annual applications of 45 t ha−1 of various organic amendments plus NPK-fertilizers had been applied. The amendments included biosolids from Vancouver, Kelowna and Penticton, biowastes from Aldergrove and Abbotsford, and peat. Yield of both chard and carrot was increased for some organic treatments plus fertilizer relative to plots receiving commercially recommended rates of NPK-fertilizer only (control plots). Leaf N, P, Zn and Cu concentrations of both crops were usually elevated, but not to toxic values, in plots receiving wastes containing high concentrations of the respective nutrients. By the end of the third growing season, extractable P, Zn and Cu increased in the surface 15 cm of soil, relative to control plots, with P and Cu i...

Availability of nitrogen from municipal biosolids for dryland forage grass.

A 3-yr study, initiated in 1996, evaluated the availability of N from applied biosolids for dryland forage grass production under the cool, continental climatic conditions in central British Columbia. Treatments included 600 (LB), 1200 (MB) and 1800 (HB) kg total N ha−1 applied as municipal biosolids, a single application of 150 kg N ha−1 as urea in the first year of the experiment (SF), a multiple application of 150, 60 and 30 kg N ha−1 as urea in the first, second, and third years of the experiment (MF), and a control that received no biosolids or urea. All treatments were roto-tilled to 15-cm depth and seeded to a mixture of four grasses. The LB treatment was predicted to supply a similar quantity of plant-available N as the MF treatment, assuming 25, 10, and 5% of biosolids N is available in the first, second, and third year, respectively. Soil N fertility was poor as indicated by the very low forage yield and N uptake in the control, and minimal apparent net soil N mineralisation. Recovery of urea N ...

Foliar N application reduces soil NO 3 − -N leaching loss in apple orchards

A comparison of the effects of foliar and soil N application was made in field-grown mature fruiting Gala/M9 apple trees (Malus domestica Borkh) in 2001 and 2002 growing seasons under Pacific Northwest growing conditions in southern British Columbia, Canada. The trees, six years old at the start of the experiment, were treated: (1) with 5 g/l urea sprays supplied every two weeks (7 times) from mid May to mid August (total about 50 g N/tree/year), (2) with the same amount of N applied to the soil with the same timing and quantity as for the foliar treatment, and (3) with no N (control). Leaf color (as SPAD readings) and N concentrations (mg/g), and soil NH4+-N and NO3−-N were measured periodically throughout the two seasons. Leached NO3−-N was monitored monthly via an anion exchange probe from June to October in 2001 and from May to November in 2002. Shoot length was measured in October and N concentration of one-year-old wood and roots was determined in December of each growing s eason. Soil N application significantly increased shoot length relative to control or foliar N application. Leaf color, leaf N, and N concentration of one-year-old wood and roots were similarly increased relative to control by both soil and foliar N application. These treatments also increased fruit yield relative to control. There was no significant difference in yield and fruit quality between soil and foliar N applications. Soil N application increased soil NH4+-N and NO3−-N content in the root zone, and also increased the NO3− leaching loss below the root zone especially late in the growing season. Our results suggested that tree N status and yield and fruit quality could be maintained by multiple urea sprays during the growing season in apple orchards, and foliar N application will reduce the risk of soil NO3−-N leaching.

Potential impacts of climate change on water availability for crops in the Okanagan Basin, British Columbia

Crop water demand in the Okanagan Basin was determined for 1961 to 1990, 2010 to 2039, 2040 to 2069, and 2070 to 2099. Daily station temperature data were spatially interpolated to a 1 × 1 km grid and adjusted for elevation. Daily precipitation data were estimated across four climatic regions. Output from three global climate models (GCM), CGCM2, CSIROMk2 and HadCM3 was used to create future daily climate. Daily potential evapo-transpiration (grass reference) was estimated from an empirical relationship between Bellani- plate atmometer readings, temperature and extra-terrestrial solar radiation, and then modified by crop coefficients for all crops except pasture. Depending on GCM, projected water demand increased by 12–20% (2010 to 2039), 24–38% (2040 to 2069) and 40–61% (2070 to 2099). Possible elevated CO2 effects on stomatal conductance, which may reduce water demand, were not accounted for. Comparisons with modeled Okanagan Lake inflows indicated that, on average, high water demand and low supply scen...

Drip-fertigation of apple trees affects root distribution and development of K deficiency.

The locations of root intersections were mapped relative to micro-emitters in spring, 1996 for Gala apple (Malus domestica Borkh) on M.26 rootstock, which were established and grown for 8 yr under micro-irrigation with fertigation. Root distribution was mapped for trees that had been irrigated daily between May and October using drip or microjet systems and fertigated each year during May. Drip-irrigated trees had nearly half of their total root intersections within 30 cm depth and lateral distance from the emitter. Roots of microjet-irrigated trees were more widely distributed over a soil volume extending to 60 cm depth and 90 cm lateral distance from the trees. Leaf K concentrations had decreased to near deficient concentrations for drip-irrigated trees after 5 yr.Root distribution mapping and soil sampling were undertaken in spring 1997 for N-fertigated Gala on M.9 apples, planted in 1992 on the same soil, with or without annual K applications during 1992–1996. Fertigation of 15 g K tree−1 each year in...

Impact of climate change scenarios on Canadian agroclimatic indices

Qian, B., De Jong, R., Gameda, S., Huffman, T., Neilsen, D., Desjardins, R., Wang, H. and McConkey, B. 2013. Impact of climate change scenarios on Canadian agroclimatic indices. Can. J. Soil Sci. 93: 243-259. The Canadian agricultural sector is facing the impacts of climate change. Future scenarios of agroclimatic change provide information for assessing climate change impacts and developing adaptation strategies. The goal of this study was to derive and compare agroclimatic indices based on current and projected future climate scenarios and to discuss the potential implications of climate change impacts on agricultural production and adaptation strategies in Canada. Downscaled daily climate scenarios, including maximum and minimum temperatures and precipitation for a future time period, 2040-2069, were generated using the stochastic weather generator AAFC-WG for Canadian agricultural regions on a 0.5°×0.5° grid. Multiple climate scenarios were developed, based on the results of climate change simulations conducted using two global climate models - CGCM3 and HadGEM1 - forced by IPCC SRES greenhouse gas (GHG) emission scenarios A2, A1B and B1, as well as two regional climate models forced by the A2 emission scenario. The agroclimatic indices that estimate growing season start, end and length, as well as heat accumulations and moisture conditions during the growing season for three types of field crops, cool season, warm season and over-wintering crops, were used to represent agroclimatic conditions. Compared with the baseline period 1961-1990, growing seasons were projected to start earlier, on average 13 d earlier for cool season and over-wintering crops and 11 d earlier for warm season crops. The end of the growing season was projected on average to be 10 and 13 d later for over-wintering and warm season crops, respectively, but 11 d earlier for cool season crops because of the projected high summer temperatures. Two indices quantifying the heat accumulation during the growing season, effective growing degree days (EGDD) and crop heat units (CHU) indicated a notable increase in heat accumulation: on average, EGDD increased by 15, 55 and 34% for cool season, warm season and over-wintering crops, respectively. The magnitudes of the projected changes were highly dependent on the climate models, as well as on the GHG emission scenarios. Some contradictory projections were observed for moisture conditions based on precipitation deficit accumulated over the growing season. This confirmed that the uncertainties in climate projections were large, especially those related to precipitation, and such uncertainties should be taken into account in decision making when adaptation strategies are developed. Nevertheless, the projected changes in indices related to temperature were fairly consistent.

Irrigation frequency and quantity affect root and top growth of fertigated 'McIntosh' apple on M.9, M.26 and M.7 rootstock

A study was undertaken in order to quantify the effects of rootstock and irrigation level on the rooting pattern of fertigated apple trees. A profile trench observation method was used to map the number and location of root intersections at two planes relative to drip emitters for NP-fertigated McIntosh apple trees (Malus domestica Borkh). Four replicates of all combinations of three rootstocks (M.9, M.26 and M.7, planted in 1990) and two irrigation treatments [F1 (daily, watered to field capacity) and F2 (weekly, watered to 50% available soil water capacity, imposed in 1991)] were investigated after the 1994 growing season. Dwarfing rootstocks and F2-irrigation had lower top vigour and yield per tree. Cumulative yield efficiency was greater for trees on dwarfing rootstock but was unaffected by irrigation treatment. Root numbers per observation plane paralleled rootstock vigour, being lowest for M.9 and greatest for M.7. No effect of irrigation on root number was observed. Root distribution was affected b...