Gulf Coast Riceland Seed Biomass Estimates for Waterfowl Habitat Conservation

Biomass estimates of potential waterfowl foods are fundamental to estimating foraging carrying capacity of waterfowl habitat by conservation planners and managers of the North American Waterfowl Management Plan-Gulf Coast Joint Venture (GCJV). Rice and moist-soil seeds in Gulf Coast rice fields provide principal sources of energy for waterfowl during migration and winter. We investigated spatio-temporal biomass dynamics of these seeds and modeled their variation in production and idled rice fields in southwestern Louisiana, southeastern Texas, and the Texas Mid-Coast, USA, in August and November 2010–2013. We hypothesized that previous estimates of November rice and moist-soil seed biomass from the Mississippi Alluvial Valley were not applicable to the GCJV region because climate and agricultural production practices (e.g., ratooning, crayfish [Procambrus spp.] aquaculture) are primary inter-regional contrasts. Waste-rice biomass was greatest in November in fields with an unharvested second crop of rice from tillers of original plants (i.e., ratoon crop; 837.7 kg[dry]/ha; CV = 16.7%) and least in fields without a ratoon crop (119.3 kg/ha; CV = 18.5%). Moist-soil seed biomass was greatest in idled rice fields in October (477.3 kg/ha; CV = 24.8%), where substrate and rice stubble were disked at the time of sampling, and in idled fields with standing native vegetation in November (304.8 kg/ha; CV = 17.1%). Field-level variation in waste rice in production fields in November was best explained by an interaction between field management (e.g., harvested ratoon) and rice variety. We were unable identify a reliable predictor of field-level variation in moist-soil seed biomass in idled fields for July–August or November (i.e., null model was best or competitive). Substituting existing seasonal moist-soil and rice seed biomass estimates in GCJV planning models with those from our study would result in a seasonally flooded habitat objective 76% (101,974 ha) greater than the current GCJV estimate for 3 rice-growing planning areas. We encourage conservation planners in the GCJV region to use biomass estimates from our study because they are reasonably precise for planning and implementation (i.e., CV ~ 20%) and represent most contemporary patterns of farming practices and food abundance in this region. Further, programs and incentives that promote production of ratoon rice crops and allow growth of naturally occurring vegetation in idled rice fields, followed by shallow flooding during November–February, would significantly enhance food resources for waterfowl and other waterbirds in this important landscape for North American avifauna. © 2020 The Wildlife Society.     

Depletion of Rice as Food of Waterfowl Wintering in the Mississippi Alluvial Valley

ABSTRACT Waterfowl habitat conservation strategies in the Mississippi Alluvial Valley (MAV) and several other wintering areas assume carrying capacity is limited by available food, and increasing food resources is an effective conservation goal. Because existing research on winter food abundance and depletion is insufficient to test this hypothesis, we used harvested rice fields as model foraging habitats to determine if waste rice seed is depleted before spring migration. We sampled rice fields (n = 39 [winter 2000–2001], n = 69 [2001–2002]) to estimate seed mass when waterfowl arrived in late autumn and departed in late winter. We also placed exclosures in subsets of fields in autumn (n = 8 [2000–2001], n = 20 [2001–2002]) and compared seed mass inside and outside exclosures in late winter to estimate rice depletion attributable to waterfowl and other processes. Finally, we used an experiment to determine if the extent of rice depletion differed among fields of varying initial abundance and if the seed mass at which waterfowl ceased foraging or abandoned fields differed from a hypothesized giving-up value of 50 kg/ha. Mean seed mass was greater in late autumn 2000 than 2001 (127.0 vs. 83.9 kg/ha; P = 0.018) but decreased more during winter 2000–2001 than 2001–2002 (91.3 vs. 55.7 kg/ha) and did not differ at the end of winter (35.8 vs. 28.3 kg/ha; P = 0.651). Assuming equal loss to deterioration inside and outside exclosures, we estimated waterfowl consumed 61.3 kg/ha (48.3%) of rice present in late autumn 2000 and 21.1 kg/ha (25.1%) in 2001. When we manipulated late-autumn rice abundance, mean giving-up mass of rice seed was similar among treatments (48.7 kg/ha; P = 0.205) and did not differ from 50 kg/ha (P = 0.726). We integrated results by constructing scenarios in which waterfowl consumed rice at different times in winter, consumption and deterioration were competing risks, and consumption occurred only above 50 kg/ha. Results indicated waterfowl likely consumed available rice soon after fields were flooded and the amount consumed exceeded our empirical estimates but was ≤48% (winters pooled) of rice initially present. We suggest 1) using 50 kg/ha as a threshold below which profitability limits waterfowl feeding in MAV rice fields; 2) reducing the current estimate (130 kg/ha) of rice consumed in harvested fields to 47.1 kg/ha; and 3) increasing available rice by increasing total area of fields managed, altering management practices (e.g., staggered flooding), and exploring the potential for producing second or ratoon rice crops for waterfowl.     

Trade‐offs among agronomic,energetic, and environmental performance characteristics of corn and prairie bioenergy cropping systems

Cellulosic bioenergy production provides opportunities to utilize a range of cropping systems that can enhance the multifunctionality of agricultural landscapes. In a 9‐ha field experiment located on fertile land in Boone County, IA, USA, we directly compared a corn‐soybean rotation harvested for grain, continuous corn harvested for grain and stover, continuous corn harvested for grain and stover with a rye cover crop, newly reconstructed prairie harvested for biomass and fertilized with nitrogen, and unfertilized newly reconstructed prairie harvested for biomass. Comparisons were made using four performance indicators: harvestable yield, net energy balance (NEB), root production, and nutrient balances. We found trade‐offs among systems in terms of the measured performance indicators. Continuous corn systems were the highest yielding, averaging 13 Mg ha^?1 of harvested biomass (grain plus stover), whereas fertilized and unfertilized prairies produced the least harvested biomass at 8.8 and 6.5 Mg ha^?1, respectively. Mean NEBs were highest in continuous corn systems at 45.1 GJ ha^?1, intermediate in the corn‐soybean rotation at 28.6 GJ ha^?1, and lowest in fertilized and unfertilized prairies at 11.4 and 10.5 GJ ha^?1, respectively. Concomitant with the high yields of the continuous corn systems were the large nutrient requirements of these systems compared to the prairie systems. Continuous corn with rye required three times more nitrogen inputs than fertilized prairie. Root production, on the other hand, was on average seven times greater in the prairie systems than the annual crop systems. On highly fertile soils, corn‐based cropping systems are likely to play an important role in maintaining the high productivity of agricultural landscapes, but alternative cropping systems, such as prairies used for bioenergy production, can produce substantial yield, require minimal externally derived inputs, and can be incorporated into the landscape at strategic locations to maximize the production of other ecosystem services.     

Agricultural practices and residual corn during spring crane and waterfowl migration in Nebraska

Nebraska's Central Platte River Valley (CPRV) is a major spring-staging area for migratory birds. Over 6 million ducks, geese, and sandhill cranes (Grus canadensis) stage there en route to tundra, boreal forest, and prairie breeding habitats, storing nutrients for migration and reproduction by consuming primarily corn remaining in fields after harvest (hereafter residual corn). In springs 2005–2007, we measured residual corn density in randomly selected harvested cornfields during early (n = 188) and late migration (n = 143) periods. We estimated the mean density of residual corn for the CPRV and examined the influence of agricultural practices (post-harvest field management) and migration period on residual corn density. During the early migration period, residual corn density was greater in idle harvested fields than any other treatments of fields (42%, 48%, 53%, and 92% more than grazed, grazed and mulched, mulched, and tilled fields, respectively). Depletion of residual corn from early to late migration did not differ among post-harvest treatments but was greatest during the year when overall corn density was lowest (2006). Geometric mean early-migration residual corn density for the CPRV in 2005–2007 (42.4 kg/ha; 95% CI = 35.2–51.5 kg/ha) was markedly lower than previously published estimates, indicating that there has been a decrease in abundance of residual corn available to waterfowl during spring staging. Increases in harvest efficiency have been implicated as a cause for decreasing corn densities since the 1970s. However, our data show that post-harvest management of cornfields also can substantially influence the density of residual corn remaining in fields during spring migration. Thus, managers may be able to influence abundance of high-energy foods for spring-staging migratory birds in the CPRV through programs that influence post-harvest management of cornfields. © 2011 The Wildlife Society.     

The Effects of Seasonal Flooding on Seed Availability for Spring Migrating Waterfowl

Abstract: We hypothesized the seed biomass available to migrating waterfowl would be higher in spring- versus fall-flooded wetlands. To test this hypothesis we conducted an experiment using 5 pairs of wetland impoundments in northern Missouri, USA (2000-2002). We strategically assigned one impoundment of each pair to either a fall or spring treatment group. We estimated seed biomass in fall and in spring by clipping seed heads and collecting soil cores at 20 random locations within each impoundment. We placed exclosures near each fall sample site in spring-flooded impoundments to estimate seed loss from granivorous birds and rodents. Despite similar biomass in fall between treatments (P = 0.64), overwinter seed loss was greater in fall-flooded (79%; 1,324 ± 195 kg/ha) than in spring-flooded (31%; 653 6 130 kg/ha) impoundments (P = 0.009). Considering barnyard grass or millet (Echinochloa spp.) only, seed loss was higher in fall-flooded than in spring-flooded impoundments (P = 0.05). Spring biomass estimates were similar inside versus outside exclosures (P = 0.63) indicating loss to granivorous birds and rodents was limited. Our results suggest that fall flooding reduces seed availability for spring migrating waterfowl. We recommend spring flooding be used in areas where impoundment water levels can be manipulated to increase seed availability for spring migrating waterfowl.     

Control of the Soybean Cyst Nematode by Crop Rotation in Combination with a Nematicide

An experiment to evaluate the control of soybean cyst nematodes compared 1-year, 2-year, and 3-year nonhost rotations with continuous soybeans (Glycine max) in 0.2-ha plots. In a second 1-year rotation, the plots were planted to soybean or corn (Zea mays) after fumigation in the spring with a split application of 1,3-dichloropropene (748.2 liters/ha). The effects of the nematicide were apparent the first year. Soybean yield was 1,482 kg/ha compared to 233 kg/ha in the untreated plots. In the second year, the highest yielding plants (2,035 kg/ha) were those following 1 year of corn that had been treated the previous year; plants in untreated plots yielded 288 kg/ha. Average yield of soybean following 1 year of corn was 957 kg/ha compared to 288 kg/ha for continuous soybean. In the third year, the effects of the nematicide were still evident. Soybean plants in plots treated the first year, followed by corn, then soybean, yielded 1,044 kg/ha compared to 761 kg/ ha for soybean following 1 year of corn and 991 kg/ha for soybean following 2 years of corn. Plots planted to soybean for 3 consecutive years yielded 337 kg/ha. Nematicidal effects were no longer evident during the fourth year. Yields were most improved by the greatest number of years in the nonhost crop; highest yields in descending order were from plants following 3 years of corn, 2 years of corn, and 1 year of corn. Plots planted to soybean for 4 consecutive years yielded 130 kg/ha. Highly significant negative correlations occurred each year between initial nematode population densities and seed yield.     

Influence of macroinvertebrates and macrophytes on waterfowl utilization of wetlands in the Prairie Pothole Region of northwestern Wisconsin

Waterfowl and limnological data were monitored on Waterfowl Production Area (WPA) wetlands in northwestern Wisconsin over a 6-yr period (1983–88) to determine the impact of macroinvertebrates and macrophytes on waterfowl utilization. Interrelationships between limnological conditions and Waterfowl Breeding Pair Densities (BPDs reported as pairs/ha water surface) were analyzed using correlation and general linear model analysis techniques.Annual changes in waterfowl BPDs differed between wetlands according to differences in the structure of macrophyte communities and basin morphometry. The strength of associations differed between the two dominant waterfowl species. In a wetland dominated by dense stands of submersed vegetation, annual fluctuations in blue-winged teal (Anas discors) BPDs corresponded directly with changes in macrophyte biomass, but not with changes in macroinvertebrate density. In a nearby less densely vegetated wetland of similar water chemistry and trophic status, fluctuations in teal BPDs corresponded directly with changes in macroinvertebrate density, but not with changes in macrophyte biomass. These associations occurred despite a significant positive correlation between macroinvertebrates and macrophyte biomass in the latter habitat. Annual fluctuations in mallard (Anas platyrhynchos) BPDs were not correlated significantly with either macrophyte biomass or macroinvertebrate density in either wetland.     

New Technology for Estimating Seed Production of Moist-Soil Plants

ABSTRACT Waterfowl biologists estimate seed production in moist-soil wetlands to calculate duck-energy days (DEDs) and evaluate management techniques. Previously developed models that predict plant seed yield using morphological measurements are tedious and time consuming. We developed simple linear regression models that indirectly and directly related seed-head area to seed production for 7 common moist-soil plants using portable and desktop scanners and a dot grid, and compared time spent processing samples and predictive ability among models. To construct models, we randomly collected approximately 60 plants/species at the Tennessee National Wildlife Refuge, USA, during September 2005 and 2006, threshed and dried seed from seed heads, and related dry mass to seed-head area. All models explained substantial variation in seed mass (R²< 0.87) and had high predictive ability (R²_predicted < 0.84). Processing time of seed heads averaged 22 and 3 times longer for the dot grid and portable scanner, respectively, than for the desktop scanner. We recommend use of desktop scanners for accurate and rapid estimation of moist-soil plant seed production. Seed predictions per plant from our models can be used to estimate total seed production and DEDs in moist-soil wetlands.     

Spatial and Temporal Variation of Roots, Arbuscular Mycorrhizal Fungi, and Plant and Soil Nutrients in a Mature Pinot Noir (Vitis vinifera L.) Vineyard in Oregon, USA

Soil and crop management practices may influence biomass growth and yields of cotton (Gossypium hirsutum L.) and sorghum (Sorghum bicolorL.) and sequester significant amount of atmospheric CO₂in plant biomass and underlying soil, thereby helping to mitigate the undesirable effects of global warming. This study examined the effects of three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)], four cover crops [legume (hairy vetch) (Vicia villosa roth), nonlegume (rye) (Secale cerealeL), hairy vetch/rye mixture, and winter weeds orno covercrop], and three N fertilization rates (0, 60–65, and 120–130 kg N ha ^–1) on the amount of C sequestered in cotton lint (lint + seed), sorghum grain, their stalks (stems + leaves) and roots, and underlying soil from 2000 to 2002 in central Georgia, USA. A field experiment was conducted on a Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults). In 2000, C accumulation in cotton lint was greater in NT with rye or vetch/rye mixture but in stalks, it was greater in ST with vetch or vetch/rye mixture than in CT with or without cover crops. Similarly, C accumulation in lint was greater in NT with 60 kg N ha ^–1 but in stalks, it was greater in ST with 60 and 120 kg N ha ^–1 than in CT with 0 kg N ha ^–1. In 2001, C accumulation in sorghum grains and stalks was greater in vetch and vetch/rye mixture with or without N rate than in rye without N rate. In 2002, C accumulation in cotton lint was greater in CT with or without N rate but in stalks, it was greater in ST with 60 and 120 kg N ha ^–1 than in NT with or without N rate. Total C accumulation in the above- and belowground biomass in cotton ranged from 1.7 to 5.6 Mg ha ^–1 and in sorghum ranged from 3.4 to 7.2 Mg ha ^–1. Carbon accumulation in cotton and sorghum roots ranged from 1 to 14% of the total C accumulation in above- and belowground biomass. In NT, soil organic C at 0–10 cm depth was greater in vetch with 0 kg N ha ^–1 or in vetch/rye with 120–130 kg N ha ^–1 than in weeds with 0 and 60 kg N ha ^–1 but at 10–30 cm, it was greater in rye with 120–130 kg N ha ^–1 than in weeds with or without rate. In ST, soil organic C at 0–10 cm was greater in rye with 120–130 kg N ha ^–1 than in rye, vetch, vetch/rye and weeds with 0 and 60 kg N ha ^–1. Soil organic C at 0–10 and 10–30 cm was also greater in NT and ST than in CT. Since 5 to 24% of C accumulation in lint and grain were harvested, C sequestered in cotton and sorghum stalks and roots can be significant in the terrestrial ecosystem and can significantly increase C storage in the soil if these residues are left after lint or grain harvest, thereby helping to mitigate the effects of global warming. Conservation tillage, such as ST, with hairy vetch/rye mixture cover crops and 60–65 kg N ha ^–1 can sustain C accumulation in cotton lint and sorghum grain and increase C storage in the surface soil due to increased C input from crop residues and their reduced incorporation into the soil compared with conventional tillage, such as CT, with no cover crop and N fertilization, thereby maintaining crop yields, improving soil quality, and reducing erosion.     

Effects of a rapidly increasing population of common carp on vegetative cover and waterfowl in a recently restored Midwestern shallow lake

Although the common carp (Cyprinus carpio), an invasive benthic fish from Eurasia, has long been strongly implicated in the disappearance of vegetative cover and reduced waterfowl abundance in North American shallow lakes, the details of this relationship are obscure. This study documented ecological changes in a recently restored shallow lake (Hennepin and Hopper Lakes, IL, USA) at a time that it was experiencing a large increase in its carp population. We estimated the abundance and biomass of carp 7 years after this lake had been restored and then back-calculated carp population size across time while examining changes in the lake’s plant and waterfowl communities. We found that the biomass of carp remained below ~30 kg/ha for 5 years following restoration, but then increased to ~100 kg/ha in the sixth year following a strong recruitment event. Although a carp biomass of <30 kg/ha had no discernible effects on vegetative cover (which exceeded 90%) or waterfowl (which exceeded 150,000 individuals during fall censuses), the increase to 100 kg/ha was associated with a ~50% decrease in both vegetative cover and waterfowl. A further increase in carp biomass to over 250 kg/ha during the seventh year coincided with a decrease in the vegetative cover to 17% of the lake’s surface and a decline in waterfowl use to ~10% of its original value. These data suggest that the common carp is extremely damaging to the ecological integrity of shallow lakes when its density exceeds ~100 kg/ha. Since the biomass of carp in Midwestern shallow lakes commonly exceeds this value by 3–4 times, it seems likely that carp are responsible for the large-scale habitat deterioration described in many of these ecosystems. Handling editor: J. Cambray     

Moist-Soil Seed Abundance in Managed Wetlands in the Mississippi Alluvial Valley

Abstract: Managed moist-soil units support early succession herbaceous vegetation that produces seeds, tubers, and other plant parts used by waterfowl in the Mississippi Alluvial Valley (MAV), USA. We conducted a stratified multi-stage sample survey on state and federal lands in the MAV of Arkansas, Louisiana, Mississippi, and Missouri during autumns 2002–2004 to generate a contemporary estimate of combined dry mass of seeds and tubers (herein seed abundance) in managed moist-soil units for use by the Lower Mississippi Valley Joint Venture (LMVJV) of the North American Waterfowl Management Plan. We also examined variation in mean seed abundance among moist-soil units in 2003 and 2004 in relation to management intensity (active or passive), soil pH and nutrient levels, proportional occurrence of plant life-forms (e.g., grass, flatsedge, and forb; vine; woody plants), and unit area. Estimates of mean seed abundance were similar in 2002 (x̄ = 537.1 kg/ha, SE = 100.1) and 2004 (x̄ = 555.2 kg/ha, SE = 105.2) but 35–40% less in 2003 (x̄ = 396.8 kg/ha, SE = 116.1). Averaged over years, seed abundance was 496.3 kg/ha (SE = 62.0; CV = 12.5%). Multiple regression analysis indicated seed abundance varied among moist-soil units inversely with proportional occurrence of woody vegetation and unit area and was greater in actively than passively managed units (R²_adj = 0.37). Species of early succession grasses occurred more frequently in actively than passively managed units (P ≤ 0.09), whereas mid- and late-succession plants occurred more often in passively managed units (P ≤ 0.02). We recommend the LMVJV consider 556 kg/ha as a measure of seed abundance for use in estimating carrying capacity in managed moist-soil units on public lands in the MAV. We recommend active management of moist-soil units to achieve maximum potential seed production and further research to determine recovery rates of seeds of various sizes from core samples and the relationship between seed abundance and unit area. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):707–714; 2008)     

Leaf protein concentrates: a comparison of protein production per acre of forage with that from seed and animal crops

The essential amino acid production for ten crops harvested for forage and fifteen crops harvested for seed was calculated from average crop yields in the United States for the ten-year period of 1953 to 1962. Highest yields per acre of essential amino acids were calculated from forages which could be processed into leaf protein concentrates. Alfalfa produced the highest yield per acre of essential amino acids of the twenty major crops; soybean seed was second. The calculated yields of edible protein and essential amino acids of leaf protein from corn were equal to or greater than the protein from the corn seed and several times that from animals fed the corn grain. At the present time, leaf protein concentrate may not be able to compete in cost with the by-product protein concentrates such as soybean meal, cottonseed meal, peanut meal, linseed meal, or tankage for feeding farm animals. However, further study of the production of leaf protein concentrates should be made to assure protein supplies for those regions where other adequate protein sources are lacking.     

Quantification of yield losses caused by leaf anthracnose on sorghum in Brazil

The leaf anthracnose disease in sorghum, caused by Colletotrichum sublineolum (Henn. ex Sacc. & Trotter), is widely distributed throughout its Brazilian cultivation areas. The disease can cause significant losses in grain yield and quality. This study aimed to quantify the effects of leaf anthracnose on grain yield of different sorghum genotypes. Two elite inbred lines of sorghum, BR009 (susceptible) and BR008 (moderately resistant), and the hybrids, BR304 and MR43 (susceptible), BRS310 and DKB599 (moderately resistant) and BRS308 and AG1060 (resistant), were planted in a complete randomized block design with three replicates. The disease severity (DS) was evaluated weekly, starting from the onset of the first foliar symptoms, and yield losses were estimated using linear regression analysis. Leaf anthracnose significantly reduced sorghum yields in the susceptible genotypes. The highest yield loss of 86% was observed in the inbred line BR009, when the disease severity reached 100%. For the hybrids, the grain yield loss varied from 35% (BRS310) to 72% (BRS308). According to the adjusted model, a grain yield reduction of 23.48 kg/ha for BR304, 14.57 kg/ha for BRS310 and 15.91 kg/ha for DKB599 was observed for every 1% increase in disease severity. We demonstrate for the first time the effect of leaf anthracnose disease on grain sorghum yields under Brazilian conditions. The results from this study provide a starting point for developing new strategies for the integrated disease management of sorghum anthracnose.     

Nodulation,accumulation and redistribution of nitrogen in soybean (Glycine max (L.) Merrill) as influenced by seed inoculation and scheduling of irrigation

Summary A field experiment was conducted on soybean (Glycine max (L.) Merrill) with a view to find out the effect of seed inoculation and scheduling of irrigation on nodulation, accumulation and re-distribution of nitrogen in plant tops and soil. The eight treatment combinations consists of two seed inoculations,viz. uninoculated and inoculated with rhizobium culture, and four irrigation schedules,viz. irrigation water to the cumulative pan evaporation (IW/CPE) ratio of 0.5, 0.7, 0.9 and a control (rainfed). Seed inoculation by, rhizobium culture increased the number, dry-weight and N content of nodules per plant. Inoculation of seeds also increased the N accumulation rate in plant top and it was 2.48 kg/ha/day during the flower-initiation to the pod-initiation stage (30–60 days interval). At harvest, 32.2, 47.8 and 26.2 kg N/ha was re-distributed from the stems, leaves and pods-wall of inoculated plants to the grains, respectively. A total of 186.5 kg N/ha was harvested and 64.7 kg N/ha, was accumulated in soil under the inoculated condition.Scheduling of irrigation at 0.7 IW/CPE proved better, than other irrigation schedules and helped in increasing the nodulation, nitrogen accumulation and grain yield. As compared to control, 8.4, 17.8 and 18.4 kg more of N/ha was redistributed from the stems, leaves and pods-wall respectively when the irrigations were scheduled at 0.7 IW/CPE ratio. Under this irrigation schedule the total N harvest was 200.1 kg/ha while the total N increased by 55.9 kg over that present in soil at the time of sowing.     

Associative effect ofAzospirilium brasilense withRhizobium japonicum on nodulation and yield of soybean (Glycine max)

Summary Azospirillum was associated with nodules of soybean. In general, seed inoculation with a broth culture ofAzospirillum brasilense alone significantly increased nodulation and grain yield of soybean grown in pots in unsterilized soil with different levels of urea ranging from 0 to 80 kg N/ha. This trend was significantly reproducible in a second experiment when a carrier based inoculant of the bacterium was used for seed inoculation.Inoculation withRhizobium japonicum andA. brasilense in combination generally increased grain yield in both the experiments, although the data were not significant.     

Modeling Water Quality Impacts of Cellulosic Biofuel Production from Corn Silage

The growing interest in the use of alternative biomass products for fuel production requires a thorough understanding of the environmental impacts associated with the production of these bioenergy crops. Corn silage is a potential bioenergy feedstock; however, water quality implications for its utilization as a biofeedstock are not understood. The objective of this work was to evaluate water quality impacts associated with corn silage production. The GLEAMS-NAPRA model was used to quantify runoff, percolation, erosion, nitrate-nitrogen, total phosphorus, and pesticide losses attributed to the production of corn silage with and without winter cover crops for two tillage options (conventional tillage and no till) on three Indiana soils. Results revealed that corn silage would generate greater annual surface runoff (1 to 6 mm) and percolation (1 to 20 mm) compared with corn grain and grain plus stover cropping systems. Silage/winter cereal rye cover crop reduced annual surface runoff and percolation and was strongly influenced by increases in evapotranspiration, when compared with continuous silage production. Silage managed with winter cereal rye cover crop influenced water quality by reducing annual nitrate losses with runoff from a low of 14 % to a high of 27 %, with relatively no effect because of tillage management. No-till practice on silage system produced significantly greater phosphorus losses (7.46 to 18.07 kg/ha) in comparison to silage/cereal rye, corn grain, and grain plus stover harvest (p?<?0.05). For every 1,000 l of ethanol produced from corn silage, erosion losses ranged from 0.07 to 0.95 t/ha for conventional tillage practices and from 0.06 to 0.83 t/ha for no-till practices. The feasibility of cropping systems such as corn silage/cereal rye could contribute to large-scale biomass production but should be further investigated.     

Waterfowl grazing effects on submerged macrophytes in a shallow mediterranean lake

Waterfowl exclusion cages were set up in Sentiz Lake, an eutrophic shallow lake in León (NW of Spain) in order to determine the role of waterfowl herbivory on macrophyte biomass and species composition. Total macrophyte biomass was high during the study (250 g DW m⁻² in summer). The macrophyte community was mainly formed by Myriophyllum alterniflorum (95% cover), Ceratophyllum demersum (5%) and Potamogeton gramineus (<0.5%). High densities of co-occurring coots (Fulica atra; 24 ind/ha) and ducks (Anas penelope, A. strepera and A. platyrhynchos; 18 ind/ha) did not have a significant effect on macrophyte biomass in the lake. There were no statistical differences between total biomass inside and outside the exclosures, although plant biomass reached a higher value inside the cages than in the lake. Biomass species composition was significantly different inside and outside exclosures; C. demersum was more abundant in the cages than in the lake. P. gramineus, almost absent in the lake, became co-dominant with M. alterniflorum in some exclosures. The detailed study of M. alterniflorum flower buds in summer showed significant herbivory by coots. Flower bud abundance was lower in the lake (35% lower in June; 85% lower in July) than under waterfowl exclusion. The effect of waterfowl on macrophyte biomass in Mediterranean wetlands seems to be negligible as compared to effects identified in northern European lakes. Apart from an important role in dispersal, waterfowl in Mediterranean areas have a strong qualitative effect on the structure of plant communities by selecting most palatable species or their reproductive structures.     

Vegetable oil replacements for petroleum oil adjuvants in Herbicide sprays

The objectives of this research were to observe plant response to vegetable oil sprays and to learn if vegetable oils — sunflower, soybean, linseed, or camelina — can replace petroleum oil as an herbicide adjuvant. Vegetable oils were sprayed on grain sorghum [Sorghum bicolor (L.) Moench.] and sunflower (Helianthus annuus L.) at 4 7 L/ha and were neither harmful nor beneficial to the crops. When used as an adjuvant postemergence with 1.68 kg/ha of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], 2.3 L/ha of vegetable oil were as effective in weed control as either 2.3 or 9.4 L/ha of petroleum oil. All atrazine treatments gave complete control of dicotyledonous weeds. But vegetable oil adjuvants with atrazine at 1.68 kg/ha gave significantly more grass weed control than atrazine alone at 2.24 kg/ha in two of five trials and were equally good in the other trials. The cost of the adjuvant is less than that of the atrazine replaced, and the initial herbicide residue in the soil is reduced by 25%.     

Transgenic corn for control of the European corn borer and corn rootworms: a survey of Midwestern farmers' practices and perceptions

In 2001, a self-administered questionnaire was sent to 1000 corn, Zea mays L., farmers in each of five states (Illinois, Indiana, Iowa, Minnesota, and Nebraska) to evaluate their perceptions of transgenic corn designed to control the European corn borer, Ostrinia nubilalis (Hübner), and corn rootworms, Diabrotica spp. Respondents returned 1,313 surveys (26.2%). Farmers with small acreages planted a greater portion of their corn (54.5%) with transgenic corn for control of European corn borer than farmers with large farms (39.2%). The majority (75.2%) of farmers use crop rotation to control the corn rootworm. Nine insecticides comprised 92.2% of the commercial soil insecticides used for control of corn rootworm larvae. More than one-third of the farmers in Illinois (33.5%) and Indiana (39.4%) treated first-year corn for corn rootworm, primarily due to western corn rootworm egg laying in soybean, Glycine max (L.). When asked whether they would plant transgenic corn protected against the corn rootworm, 35.0% of farmers responded they would, whereas 40.5% said they were unsure. The two greatest farmer concerns about transgenic corn were the ability to sell harvested grain (59.3%) and additional technology fees (54.8%). Respondents indicated that less farmer exposure to insecticide (69.9%) and less insecticide in the environment (68.5%) were the primary benefits of transgenic corn. Farmers who had no concerns about transgenic corn for rootworm control were more likely to purchase the product (46.8%). The most common refuge-planting options farmers favored were adjacent fields (30.9%) and split fields (29.9%). Farmers (21.1%) observed a yield increase (23.7 bu/ha [9.6 bu/acre]) when using transgenic corn for European corn borer control compared with non-transgenic corn. These data can help in understanding farmers' knowledge and concerns regarding transgenic corn. This information may be of value to guide researchers, extension specialists, and policy makers in designing insect resistance management and integrated pest management programs.     

Prevalence of Fusarium species of the Liseola section on selected Colombian animal feedstuffs and their ability to produce fumonisins

A total of 57 samples of feedstuffs commonly used for animal nutrition in Colombia (corn, soybean, sorghum, cottonseed meal, sunflower seed meal, wheat middlings and rice) were analyzed for Fusarium contamination. Fusarium fungi were identified at species level by means of conventional methods and the ability to produce fumonisins of the most prevailing species was determined. A total of 41 of the feedstuffs analyzed (71.9%) were found to contain Fusarium spp. Most contaminated substrates were corn (100%), cottonseed meal (100%), sorghum (80%), and soybean (80%). Wheat middlings and rice showed lower levels of contamination (40% and 20%, respectively), while no Fusarium spp. could be isolated from sunflower seed meal. The most prevalent species of Fusarium isolated were F. verticilliodes (70.8%), F.␣proliferatum (25.0%), and F. subglutinans (4.2%). All of them correspond to section Liseola.Production of fumonisins on corn by the isolated Fusarium was screened through liquid chromatography. Almost all strains of F. verticilliodes (97.1%) produced FB1 (5.6–25,846.4 mg/kg) and FB2 (3.4–7507.5 mg/kg). Similarly, almost all strains of F.␣proliferatum (91.7%) produced fumonisins but at lower levels than F.␣verticilliodes (FB1 from 6.9 to 3885.0 mg/kg, and FB2 from 34.3 to 373.8 mg/kg), while F. subglutinans did not produce these toxins. This is the first study in Colombia describing toxigenic Fusarium isolates from␣animal feedstuffs.