INTEGRATED CROP-LIVESTOCK SYSTEMS: LESSONS FROM NEW YORK,BRITISH COLUMBIA,AND THE SOUTH-EASTERN UNITED STATES

• Livestock production in North America has moved to fewer farms with greater inventories • Land application of livestock manures is a preferred nutrient recycling strategy • Confined animal feeding operations have challenges to utilize livestock manure sustainably • Integration of livestock and cropping systems is possible on a farm or among farms • Nutrient balance is needed for environmental sustainability Livestock production in the United States (US) and Canada is diverse, but shows a common trend in most livestock sectors toward fewer farms producing the majority of animal products despite a large number of farms still small in production scale. The migration to larger and more concentrated animal feeding operations in beef finishing and poultry, swine, and dairy production allows processors to streamline supplies to meet market demand for abundant, low-cost livestock products, whether that be for packaged meat, dairy products, or eggs. With concentration of livestock operations comes the challenge of managing manures. When sufficient land is available and nutrients are needed, livestock manure is an excellent nutrient source and land application is the preferred method of recycling this resource. However, when livestock production is constrained in a geographical area and animal densities are high, manure may become an environmental liability with potentially greater risk for runoff and leaching of nutrients, emission of odors, ammonia, and greenhouse gases, and release to the environment of pathogens and chemicals of emerging concern. Addressing these challenges now and into the future requires learning from mistakes and adopting successful approaches. We describe different levels of integration between livestock and crop producers in New York, British Columbia, and the south-eastern US as learning opportunities to improve economic and environmental sustainability. Examples show that effective solutions should recognize (1) manure has value and is not just a cost, (2) farmers, farm advisors, extension educators, nutrient management planners, crop advisors, nutritionists, state agency personnel, regulators, and university researchers need to be active participants in development of solutions, and (3) change to a sustainable future requires a combination of government regulation and outcome-based incentives.     

Variation in diosgenin levels among 10 accessions of fenugreek seeds produced in western Canada

A collection of 10 accessions of fenugreek (Trigonella foenum-graecum L.), an annual legume, was grown during two summers at three plot locations in western Canada to assess whether genetic (accession) and environmental factors (site and year of production) influenced levels of diosgenin, a steroidal sapogenin. The 60 harvested seed samples, each analyzed by single determinations on three subsamples of defatted and dried seed material, were hydrolyzed by a microscale procedure in water containing 2-propanol (70%) and sulfuric acid (1 M). The extracts were analyzed by capillary gas chromatography with 6-methyldiosgenin as internal standard. Diosgenin levels from mature seeds ranged from 0.28 to 0.92% (28-92 microg/10 mg). Analysis of variance on combined diosgenin levels from the three sites and two years revealed that accession, accession x year, and site x year effects were significant for diosgenin content, whereas site, year, and site x accession effects were not. Four accessions, CN 19062, CN 19067, CN 19070, and CN 19071, were identified with high levels of diosgenin on the basis of the 2-year data set. In these accessions, mean levels of diosgenin plus yamogenin from seven site years were estimated at 0.70, 0.98, 0.84, and 0.87%, respectively.     

Potential for mitigating atmospheric ammonia in Canada

Most ammonia (NH₃) emissions (85%) in Canada come from agricultural sources (400 kt/yr). There are international conventions that require countries to mitigate NH₃ emissions but there are no federal or provincial guidelines in Canada stipulating emission targets or best practices for agriculture. This study examines the potential for mitigating atmospheric NH₃ using a range of approaches. Taking current farm practices into account, employing proven low‐cost measures (low‐emission slurry application and slurry storage covers) would reduce annual emissions from livestock operations by 16 kt NH₃‐N, while using all available low‐cost measures would reduce emissions by 79 kt NH₃‐N or 26% of livestock emissions. Another 36 kt/yr could be avoided by improving fertilizer practices, so that the total potential reduction would be about 29% of all agricultural emissions. Emissions from beef cattle and pig production could be reduced by 18% if consumption was cut by 50%, with greater mitigation if production for export was reduced, although the economic and social consequences need to be considered. Mitigation practices must be viewed in the context of possible pollution swapping especially in surplus nitrogen situations. Emissions must also be considered in terms of atmospheric NH₃ transport to and from the USA, therefore bi‐national agreements to jointly reduce emissions might be needed. It may be more cost‐effective in Canada to strategically reduce emissions to minimize risks to health (from particulate matter) and the environment rather than to reduce annual national emission targets.     

Impact of 12-year field treatments with organic and inorganic fertilizers on crop productivity and mycorrhizal community structure

The effect of manure and mineral fertilization on the arbuscular mycorrhizal (AM) fungal community structure of sunflower (Helianthus annuus L.) plants was studied. Soils were collected from a field experiment treated for 12 years with equivalent nitrogen (N) doses of inorganic N, dairy manure slurry, or without N fertilization. Fresh roots of tall fescue (Festuca arundinacea Schreb.) grass collected from the field plots without N fertilization and unfumigated field soils were used as native microbial inoculum sources. Sunflower plants were sown in pots containing these soils, and three different means of manipulating the microbial community were set: unfumigated soil with fresh grass roots, fumigated soil with fresh grass roots, or fumigated soil with sterilized grass roots. Assessing the implications with respect to plant productivity and mycorrhizal community structure was investigated. Twelve AM fungal OTUs were identified from root or soil samples as different taxa of Acaulospora, Claroideoglomus, Funneliformis, Rhizophagus, and uncultured Glomus, using PCR-DGGE and sequencing of an 18S rRNA gene fragment. Sunflower plants grown in manure-fertilized soils had a distinct AMF community structure from plants either fertilized with mineral N or unfertilized, with an abundance of Rhizophagus intraradices-like (B2). The results also showed that AM inoculation increased P and N contents in inorganic N-fertilized or unfertilized plants, but not in manure-fertilized plants.     

Long-term alternative dairy manure management approaches enhance microbial biomass and activity in perennial forage grass

Removing solids from liquid dairy manure slurry reduces manure phosphorus (P) and increases the available (mineral) fraction of nitrogen (N) but also decreases the organic matter content of the manure. While this novel treatment reduces environmental concerns associated with excess N and P application to soils, it may also reduce microbial biomass and activity in soil. This study evaluated the long-term effects of this alternative manure treatment compared to more typical nutrient applications in a perennial grass sward (tall fescue, Festuca arundinacea Schreb.) on soil microbial biomass, community composition, hydrolytic enzyme activity, and forage yield. Nutrient treatments for this long-term field experiment in Agassiz, British Columbia, Canada were started in 2003. The treatments included liquid dairy manure slurry, liquid dairy manure with solids removed, commercial fertilizer, a combination of fertilizer and dairy manure, and a control. All treatments were applied at 400–600 kg total N ha^?1 year^?1 in four equal doses. Soil microbial community composition (phospholipid fatty acid analysis) and activity (hydrolytic enzyme activity) were determined several times during the 2013 and 2014 growing seasons to a depth of 15 cm. Time of sampling (date) had a strong influence on microbial biomass, community composition, and activity, while the response to soil properties and yield was more varied. All manure treatments (dairy manure slurry, liquid fraction, and the combination) increased microbial biomass (by 19–32%) and the potential activity of cellulose-degrading enzymes (by 31–47%) compared to commercial fertilizer and unamended plots. The commercial fertilizer and liquid fraction lowered fungal/bacterial ratios compared with both whole manure and unamended plots. Our results indicate that separating the solid from the liquid fraction of manure, to improve crop yield and reduce P loading, did not reduce microbial community size and activity and that all manure treatments increased microbial biomass and activity compared to mineral fertilizer application.     

Irrigation influences on growth, yield, and water use of persimmon trees

A 3-year irrigation trial provided basic information on the response of persimmon (Diospyros kaki cv. Triumph) water use and development to irrigation levels. Constant experimental factors applied to recommended “baseline” crop factors resulted in ratios of irrigation (I) to FAO56 reference crop evapotranspiration (ET₀) ranging from 0.35 to 1.14. Vegetative and reproductive growth, sap flow, stem water potential (SWP), and local climate were monitored. An overall increase in yield and vegetative growth in response to irrigation was found, which suggests a potential yield increase for higher irrigation levels (40 tons/ha for annual irrigation of 1,000 mm). At high irrigation, the yield response curve levelled off and the marginal contribution of additional water declined. The up to threefold increase in number of fruits with irrigation, with no influence on natural abscission, suggests that differences in fruit quantities stem from response to irrigation at the earlier growth stages. Mean fruit size and fruit quality, as indicated by the ratio of rejected fruit, increased with irrigation up to I/ET₀ of ~0.8. Relative yield increased linearly with relative transpiration. However, post-harvest quality was not influenced. SWP, sap flow, and non-transpirable water fractions indicated that the seasonal irrigation tables were not well tuned. Initial adjustments were made during the final season of the experiment and a new table was developed based on our results. The new table should be a basis for further trials.     

Effect of irrigation water salinity on transpiration and on leaching requirements: A case study for bell peppers

Maximization of crop yields when the salinity of irrigation water is high depends on providing plant transpiration needs and evaporative losses, as well as on maintaining minimum soil solution salinity through leaching. The effect of the amount of applied irrigation water was studied regarding transpiration, yields, and leaching fractions as a function of irrigation water salinity. Bell pepper (Capsicum annum L. vars. Celica and 7187) in protected growing environments in the Arava Valley of Israel was used as a case study crop to analyze water quantity–salinity interactions in a series of lysimeter, field and model simulation experiments. Leaching fraction was found to be highly influenced by plant feedback, as transpiration depended on root zone salinity. Increased application of saline irrigation water led to increased transpiration and yields. The higher the salinity level, the greater the relative benefit from increased leaching. The extent of leaching needed to maximize yields when irrigating with saline water may make such practice highly unsustainable.     

Responses of grassland soil nematodes and protozoa to multi-year and single-year applications of dairy manure slurry and fertilizer

In order to improve understanding of how long-term use of manure affects nitrogen cycling processes, the effects of multiple years of manure applications on abundance of protozoa and nematode community structure were assessed. Plots of a grass sward in the Fraser Valley of British Columbia were either left untreated or were treated with dairy manure slurry or fertilizer, each at 50 or 100 kg NH₄-N ha⁻¹, two to four times per year for six consecutive years. Nematode community structure and protozoan abundance were determined at 19 sample dates during the fourth (1997), fifth (1998) and sixth (1999) years of application. Protozoa, bacterivorous nematodes and fungivorous nematodes were consistently more abundant in soil treated with manure at both rates than in fertilized and untreated soil, indicating that microbial turnover and flux of nutrients through the soil food web was enhanced in manured soil relative to fertilized or untreated soil. The Maturity Index (MI) and the MI2-5 were both reduced by fertilization and manure, relative to the control. The MI for the manure treatment was lower than for the fertilizer treatment as a result of greater relative abundance of enrichment opportunist nematodes in manure-treated soil. Accordingly, the MI2-5 did not differ between the manure and fertilizer treatments, suggesting that with the exception of enrichment opportunists fertilizer and manure have similar effects on structural complexity of the soil food web.Populations of micro-fauna were also assessed through 1998 and 1999 in subplots that had been treated with manure or fertilizer for four years and stopped receiving manure or fertilizer in 1998, and in subplots given manure in 1998 that had previously either been fertilized or left untreated. Protozoa and bacterivorous and fungivorous nematodes remained more abundant through 1998 and 1999 in previously manure-treated plots than in previously fertilized plots, indicating that the cumulative effects of manure application on enhancement of microbial production can be detected through at least two growing seasons after applications cease. Application of manure for one year to previously non-treated or fertilized soil raised the abundance of protozoa and bacterivorous and fungivorous nematodes to levels comparable to continuously manured soil.