Precision placement of separated dairy sludge improves early phosphorus nutrition and growth in corn ( L.).

Efficient use of manure nutrients by crops is necessary to minimize losses to the environment. This field study examined the possibility of replacing side-banded mineral P with precision-placed high-P sludge (6.2-11.0% dry matter) obtained after settling dairy manure slurry. The sludge was injected at about 30 kg P ha (36.0-51.2 m ha) into the soil at corn row spacing, and the corn was planted 5, 10, and 15 cm beside the injection furrow. Controls included no added P and side-banded commercial P fertilizer. The treatments were tested on corn with low and high root colonization by arbuscular mycorrhizae (AM). The study showed that sludge did not impede AM root colonization, corn germination, or seedling growth. Corn plants with both high and low levels of AM colonization responded to the sludge from the three-leaf stage and showed the greatest benefit at the six-leaf stage. Corn responded more to sludge placed at 5 than at 15 cm from the corn rows, whereas the response at the 10-cm spacing was intermediate. There was little difference in seedling growth or final harvest parameters between the side-banded fertilizer P and the 5-cm sludge treatment. The results show a new way to use manure nutrients, namely precision-placement sludge for corn. This may obviate the need for chemical fertilizers for improving farm nutrient balances. Other anticipated benefits are less energy use for hauling and injection of the sludge fraction and reduced risk of nutrient loss by runoff and volatilization (ammonia) and nuisance odors due to injection.

Agronomic effects of multi-year surface-banding of dairy slurry on grass.

Sleigh-foot application of slurry manure is the best method for applying slurry manure on many forage fields. This study was designed to assess agronomic effectiveness of multi-year surface banding of dairy slurry on a sward of tall fescue (Festuca arundinacea Schreb.). Our study showed that with this application technology, crop recovery of total-N from applied manure in the long-term is only about 77% that of mineral fertilizer. Despite relative inefficiency of N uptake from manure, yield response to manure equaled that to fertilizer at equivalent total-N rates although N-recovery was significantly lower. About 26-32% of applied manure-N was stored in soil organic matter and the buildup of soil-N was related to application rate of organic N. At moderate applications rates (approx. 400 kg Nha(-1)a(-1)), soil N accumulated at about 120 kg ha(-1) annually compared to 98 kg ha(-1)a(-1) of unaccounted N, much of that probably volatilized and denitrified. Alternating between manure and fertilizer improved productivity per unit land area without increasing the rate of N non-recovery per unit of feed produced.

Seasonality and breeding success of captive and wild Tasmanian devils (Sarcophilus harrisii).

The synchrony and timing of reproductive events are crucially important factors to maximize individual and offspring survival, especially in seasonal environments. To increase our understanding of the physiological basis of seasonality and the influence of associated environmental factors (maximum temperature, day length and rate of day length change associated with different latitudes) on reproduction in Tasmanian devils, we reviewed records and research data from captive facilities throughout Australia in comparison to those from a wild population study (1974-1987). Overall, breeding activity began 2 weeks earlier in the captive than the wild population (week 5.7 ± 0.6 versus week 7.7 ± 0.5 for devils entering into estrus during the first two week phase; n = 24 and n = 23 respectively). If the timing of reproductive activity is considered against absolute day length rather than date, both the captive and wild populations displayed similar distributions (12.9 ± 0.7 h versus 13.0 ± 0.7 h respectively; P < 0.01) confirming day length as a proximal cue involved in eliciting a physiological response to trigger seasonal reproductive activity regardless of location. Wild devils had a higher breeding success (75%; n = 169 versus 43%; n = 115) and larger litter size (3.4 ± 0.9 versus 2.8 ± 1.1 joeys per litter) than captive devils (P < 0.05). Mean maximum temperature at the onset of reproductive activity (P < 0.05) was higher for the captive than the wild population (28.1 ± 4.0 °C versus 22.3 ± 2.7 °C respectively). The drivers for reproductive success in captive Tasmanian devils are likely multifactorial, but our results suggest that elevated temperatures associated with shifts in breeding activity and geographical location should be examined further.

Impacts of Sustained Use of Dairy Manure Slurry and Fertilizers on Populations of Pratylenchus penetrans under Tall Fescue.

Various manures and composts have been reported to reduce population densities of plant-parasitic nematodes. Dairy manure slurry is often used as a primary source of nitrogen for forage crops. This study was conducted to determine the effects of dairy manure on population densities of Pratylenchus penetrans parasitizing tall fescue. Beginning in 1994, dairy manure and inorganic fertilizer were applied after each harvest (2 to 4 times/year) at rates of 50 and 100 kg NH-N/ha; control plots were not treated. Nematode populations in soil and roots were determined at 19 sample dates during the fourth (1997), fifth (1998), and sixth (1999) years of manure and fertilizer applications. The sustained use of dairy manure and fertilizer increased population densities of P. penetrans. Our results contrast with many previous studies demonstrating that application of manures decreases population densities of plant-parasitic nematodes. Frequent applications of moderate amounts of manure to a perennial grass crop may have prevented the development of nematode-toxic levels of ammonia or other toxic substances such as nitrous acid or volatile fatty acids. Two years with no additional manure applications were required for P. penetrans population densities to return to levels similar to fertilized or untreated soil.

Winter Survival of Pratylenchus scribneri.

Population densities of Pratylenchus scribneri in a Plainfield loamy sand soil were sampled from 1 October to 1 May for 4 years. From May to October of each year, the site was planted to Russet Burbank potato and Wis 4763 corn. Percentages of change in population densities of nematodes were computed on the basis of number of nematodes present on 1 October. The decline of P. scribneri between growing seasons was nonlinear, with most mortality occurring in the autumn before the soil froze. Winter survival, defined as the percentage of change in population densities from 1 October to 1 May the following year, ranged from 50 to 136% for nematodes in corn plots and from 15 to 86% for nematodes in potato plots. There was no difference in survival of nematodes of different life stages or among root and soil habitats. Winter survival of nematodes was density-dependent in 3 of 4 years in corn plots and in 1 of 4 years in potato plots. Although predators were present, their abundance was not correlated with the winter survival of nematodes. Cumulative and average snow cover was correlated with the survival of nematodes associated with corn but not with potato. No relationships between other climatic factors and survivorship were detected.

Nematode autofluorescence and its use as an indicator of viability.

Representatives of 15 nematode genera were viewed with 450-490-nm epi-illumination and found to autofluoresce. The autofluorescence was limited to 1-5-mum-d globules in the intestinal cells of live nematodes. When adult Pratylenchus penetrans or Caenorhabditis elegans were killed with formaldehyde, freezing, or heat, autofluorescence dispersed throughout the body. Mixed stages of P. penetrans were killed by freezing at several different temperatures. Estimates of survival based on autofluorescence dispersal matched estimates based on mobility more closely than did estimates based on the vital stain, eosin-y.

Impact of Thermal History on Tolerance of Meloidogyne hapla Second-stage Juveniles to External Freezing.

Low temperature induced physiological changes that increased the ability of second-stage juveniles of Meloidogyne hapla to survive external freezing. Second-stage juveniles in polyethylene glycol solution were exposed to -4 , 0, 4, or 24 C, and then their survival was determined after ice-induced freezing of the suspensions at - 4 C for 24 hours. Survival was greatest for juveniles exposed to 4 C before freezing. Some juveniles were killed by exposure to - 4 C before freezing of the suspensions. The percentage of juveniles surviving freezing increased from about 30% to 80% within 12 hours of exposure to 4 C. This tolerance of external freezing was lost during subsequent exposure to 24 C. Longer exposures, of 1 to 15 days, to low temperature did not increase the percentage surviving external freezing, as compared to the 12-hour exposure, but reduced the tolerance of external freezing lost during subsequent exposure to 24 C for 48 hours.

Cold Hardening of Meloidogyne hapla Second-stage Juveniles.

The effect of previous exposure to low temperatures on freezing tolerance was determined for second-stage juveniles of Meloidogyne hapla. Juveniles in 5% polyethylene glycol 20,000 were exposed to 0-24 C for 12-96 hours, and then freezing tolerance was assessed by freezing samples at -4 C for 24 hours, thawing, and determining survival. Freezing tolerance was inversely related to prefreeze temperatures of 4-24 C. Prefreeze exposure to 4 C resulted in fourfold greater freezing tolerance than did exposure to 24 C. Mortality occurred during prefreeze exposure to 0 C. Most of the increase in freezing tolerance at 4 C occurred during the first 12 hours. In soil, prefreeze exposure to 4 C resulted in greater freezing tolerance than did prefreeze exposure to 24 C.

Temporal Changes in the Vertical Distribution of Pratylenchus penetrans under Raspberry.

Population densities of Pratylenchus penetrans and the biomass of fine roots of raspberry at depths of 0-5, 5-10, 10-20, and 20-30 cm were determined every 2 weeks for 2 years. The vertical distribution of P. penetrans varied from season to season, but the seasonal changes were not similar for the 2 years. In most seasons, the greatest population density was in the 5 to 10-cm-depth interval. Population densities of P. penetrans were not consistently correlated with the vertical distribution of raspberry roots in any season.

Pseudomonas chlororaphis Strain Sm3, Bacterial Antagonist of Pratylenchus penetrans.

The interaction of Pseudomonas chlororaphis strain Sm3 and the root-lesion nematode Pratylenchus penetrans was investigated in three separate greenhouse experiments with soils from southern British Columbia, Canada. The bacteria were applied to the roots of strawberry plants and planted in unpasteurized field soils, with natural or supplemented infestation of P. penetrans. Nematode suppression in roots was evident after 6 or 10 weeks in all experiments. Root or shoot growth were increased after 10 weeks in two experiments. Population dynamics of P. chlororaphis Sm3 in the rhizosphere was followed using an antibiotic-resistant mutant of P. chlororaphis Sm3. There was no apparent correlation between bacterial density in the rhizosphere and P. penetrans suppression in strawberry roots and rhizosphere soil, although the soil with the highest nematode reduction also had the largest P. chlororaphis Sm3 population in the rhizosphere.

Population Growth of Pratylenchus penetrans on Winter Cover Crops Grown in the Pacific Northwest.

Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass x sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest.

Plant-Parasitic Nematodes Associated with Grapevines, Vitis vinifera, in Oregon Vineyards.

A survey of vineyards in western Oregon was conducted in 1994 and 1995 to determine the association of plant-parasitic nematodes with vine health. Seventy vineyards in four regions of western Oregon (16 to 21 vineyards per region) were sampled. The regions were the northern, middle, and southern Willamette Valley, and southern Oregon. Vineyards were selected and partitioned into blocks by variety, age of planting, crop history, and soil characteristics. Mesocriconema xenoplax, Xiphinema americanum, Pratylenchus spp., and Paratylenchus spp. were recovered from more than 85% of the vineyards; only 10% of vineyards had detectable populations of Meloidogyne hapla. Mesocriconema xenoplax and X. americanum were found in 20% and 8% of vineyard blocks, respectively, at population densities reported to cause moderate yield loss in California. Mesocriconema xenoplax was found at greatest population densities in vineyards older than 10 years and on former Prunus orchard sites in the northern Willamette Valley. Populations of Mesocriconema xenoplax and X. americanum were associated with both healthy and stunted vines. The long-term impact of M. xenoplax, X. americanum, and other nematodes on Oregon vineyard production has not yet been determined.