Gerry H. 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.

Effect of soil cadmium application and pH on growth and cadmium accumulation in roots, leaves and fruit of strawberry plants (Fragaria × ananassa Duch.)

Three strawberry (Fragaria × ananassa Duch.) cultivars Rainier, Totem and Selva were grown under greenhouse conditions in a Parkhill sandy loam soil with a background DTPA-extractable Cd concentration of 0.18 mg kg-1 and a pH of 5.1. Experimental treatments included combinations of 4 Cd applications (0, 15, 30 and 60 mg Cd kg-1 soil) applied as CdSO4 and 2 soil pH values 5.1 and 6.8. Both the application of Cd and pH of the soil significantly affected plant growth, yield and Cd accumulation in plant tissue anf fruit. Although roots accumulated the highest concentrations of Cd of all plant parts investigated, increased soil Cd application reduced leaf weight more than root weight. In general, yield of strawberries was decreased by an increase in amount of soil-applied Cd, however the yield response varied among cultivars. At 60 mg Cd kg-1 soil, yield of Rainier cultivar was reduced to 17.6% of control plants. Over 90% of total Cd taken up by plants grown in Cd-treated soil accumulated in roots, regardless of the Cd level in the soil. Root Cd concentrations ranged from 2.6 mg kg-1 (control plants) to 505.7 mg kg-1 (Totem plants grown in soil at highest Cd and a soil pH 5.1) and were directly related to soil Cd concentrations. Cd translocation from roots to leaves and fruit was very limited, resulting in a maximum Cd concentration in root leaf tissue of 10.2 mg kg-1. Accumulation of Cd in fruit was found to correlate well with leaf Cd, although even at the highest amount of applied Cd, fruit Cd concentration did not exceed 700 μg kg-1 of fresh weight.

EFFECTS OF THREE ROOTSTOCKS ON PHOTOSYNTHESIS, LEAF MINERAL NUTRITION, AND VEGETATIVE GROWTH OF “BC-2 FUJI” APPLE TREES

Net photosynthesis (Pn), leaf nutrition, and current terminal shoot (CTS) growth of ‘BC-2 Fuji’ apple [Malus sylvestris (L.) Mill var.domestica (Borkh.) Mansf.] trees on three rootstocks, Budagovski (Bud.) 9, Ottawa 3, and M.7 EMLA under field conditions were studied in 1998 and 1999. Rootstock affected the scion leaf Pn, leaf mineral concentrations, and vegetative growth. Leaves of trees on Bud.9 had lower Pn than those on the other rootstocks, and the differences were significant in 1999. Scion leaves on Bud.9 had higher calcium (Ca) and manganese (Mn) but lower potassium (K) concentrations than those on the other rootstocks. Leaves of trees on M.7 EMLA had significantly higher magnesium (Mg), K, and copper (Cu) concentrations than those on the other rootstocks in both years. Trees on Ottawa 3 had significantly lower leaf Cu concentrations than those on the other rootstocks during both 1998 and 1999. Trees on Bud.9 rootstock had shorter limbs and terminal shoots than those on the other rootstocks in 1998 and 1999.

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...

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.

Interactive Effects of Potassium and Calcium on K/Ca Ratio and Its Consequences on Apple Fruit Quality in Calcareous Soils of Iran

Abstract This research was carried out during the 2000–2001 growing season in a low-density orchard, on a calcareous soil (Fine loamy, mixed, mesic Typic Calcixerept) in northwest Iran, using 25-year old “Golden Delicious” (Malus domestica Borkh.) apple trees on M.9 rootstock. The interactive effects of potassium (K) and calcium (Ca) on K/Ca ratio and its consequences on apple fruit quality were studied. Treatments included: T 1 = control [nitrogen (N), phosphorus (P), and manure]; T 2 = T 1 + micronutrients (deep placement) based on soil test recommendations; T 3 = T 2 + (KCl)1 based on soil test recommendations; T 4 = T 3 + spray of CaCl2 at four times; T 5 = same as T 4 but sprayed at eight times; T 6 = T 2 + (KCl)2 (50% above soil test); T 7 = T 6 + spray of CaCl2 at four times; T 8 = same as T 7 but sprayed at eight times; T 9 = same as T 8 but with an equal amount of K from K2SO4 source. Leaf samples were collected in early July and fruit samples collected in early October and were analyzed for N, K, and Ca. Thirty fruit samples were randomly selected and stored at 1°C for 45 or 90 days prior to determination of their storage life. There was a range in K and Ca level in the leaves, although both K and Ca concentrations exceeded their critical threshold values. The concentration of K in the fruit was high, but Ca was low. There was a positive correlation between leaf K and fruit K and between fruit K and total soluble solids concentration (SSC); between fruit Ca and apple fruit firmness; but negative correlations existed between K/Ca ratio and apple fruit firmness at harvest. Apple fruit SSC was increased by K-fertilization and storage period. Fruit firmness in harvest samples was the highest in plots which had received Ca sprays. Apple firmness at harvest was generally low for all treatments and reduced by duration of storage and differences among treatments were not large after 90-day storage. Variation of K/Ca ratio in the apple leaves was slight (0.9–1.4), but a wide range was observed for fruit (19–46). The highest ratio (46) occurred for T 6 and the lowest ratio (19) for T 8 and T 9. An inverse relationship between K/Ca ratios and fruit firmness indicated that on calcareous soils, at least 8-foliar applications of CaCl2 solution were necessary for “Golden Delicious” apple. #Contribution no. 2191, PARC-Summerland.

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...

Effects of preplant inoculation of apple (Malus domestica Borkh.) with arbuscular mycorrhizal fungi on population growth of the root-lesion nematode, Pratylenchus penetrans

Six species of arbuscular mycorrhizal (AM) fungi (Glomus aggregatum, G. clarum, G. etunicatum, G. intraradices, G. mosseae and G. versiforme) were evaluated, in three greenhouse experiments, for their effects on reproduction of the root-lesion nematode, Pratylenchus penetrans, and growth of Ottawa 3 apple rootstock. Glomus mosseae increased total dry weights of nematode-inoculated and non-inoculated rootstock in all three greenhouse experiments, and G. intraradices increased dry weights in two of three greenhouse experiments. Plants inoculated with G. mosseae generally supported fewer P. penetrans per gram of root than plants inoculated with other AM fungi, but did not differ significantly from the controls in any greenhouse experiment. Colonization of roots by AM fungi was reduced by P. penetrans at initial inoculum densities greater than 250 nematodes/L soil. In field trials, preplant inoculation with either G. intraradices or G. mosseae increased rootstock growth and leaf concentrations of P, Mg, Zn and Cu in fumigated plots but not in non-fumigated plots, indicating that colonization by native AM fungi in non-fumigated plots may have been sufficient for adequate nutrient acquisition. The abundance of vesicles and arbuscules was greater in roots of plants inoculated with AM fungi before planting than in roots of non-inoculated plants, in both fumigated and non-fumigated plots. P. penetrans per gram of root and per 50 ml soil were significantly lower for G. mosseae- inoculated plants than for non-inoculated plants in fumigated soil but not in non-fumigated soil.