Francis Zvomuya

Climate and agricultural land use change impacts on streamflow in the upper midwestern United States

Increased streamflow and its associated impacts on water quality have frequently been linked to changes in land use and land cover (LULC) such as tile drainage, cultivation of prairies, and increased adoption of soybeans (Glycine max) in modern day cropping systems. This study evaluated the relative importance of changes in precipitation and LULC on streamflow in 29 Hydrologic Unit Code 008 watersheds in the upper midwestern United States. The evaluation was done by statistically testing the changes in slope and intercept of the relationships between ln(annual streamflow) versus annual precipitation for the periods prior to 1975 (prechange period) and after 1976 (postchange period). A significant shift either in slope or intercept of these relationships was assumed to be an indication of LULC changes whereas a lack of significant shift suggested a single relationship driven by precipitation. All 29 watersheds showed no statistical difference in slope or intercept of the relationships between the two periods. However, a simpler model that kept the slope constant for the two periods showed a slight upward shift in the intercept value for 10 watersheds in the postchange period. A comparison of 5 year moving averages also revealed that the increased streamflows in the postchange period are mainly due to an increase in precipitation. Minimal or the lack of LULC change impact on streamflow results from comparable evapotranspiration in the two time periods. We also show how incorrect assumptions in previously published studies minimized precipitation change impacts and heightened the LULC change impacts on streamflows.

Response of russet norkotah clonal selections to nitrogen fertilization

The low vine vigor and high N requirement of Russet Norkotah may lead to N loss and groundwater contamination on coarse-textured soils. Recent clonal selections from Texas have produced strains that have larger and stronger vines, which may alter N requirements. This twoyear study examined the N use efficiency (NUE), yield, and quality of Russet Norkotah strain selections fertilized with different N levels on a Hubbard loamy sand in central Minnesota. The selections, Texas Norkotah Strain (TXNS) 112, TXNS 223, and TXNS 278 were grown with standard Russet Norkotah under irrigated conditions and received total N levels of 28, 112, 224, or 336 kg ha-1. Total, marketable, and large (>340 g) tuber yields increased linearly (P>0.05) with rate of N application in 1998 but not in 1997. The genotype main effect was not significant for any of the tuber yield parameters measured based on fresh weight. Vine, tuber, and total dry biomass yields were 116%, 5.8%, and 13.2%, respectively, higher with the selections than Russet Norkotah. Harvest index (HI), or the proportion of total dry matter partitioned to tubers, was 7% greater for Russet Norkotah than the TXNS selections, reflecting the larger vine growth of the selections. The selections accumulated significantly higher N in the vines (0.113 kg kg-1 N) than the standard clone (0.053 kg kg-1 N) as N rate increased from 28 to 336 kg ha-1, and the difference between the selections and the standard clone was larger at higher N rates than at lower N rates. Russet Norkotah partitioned 10% more N to tubers than did the TXNS selections, reflecting the difference in HI between the standard cultivar and its clones. Nitrogen recovered from fertilizer N applied in addition to the 28 kg ha-1 starter N (NUE28) averaged 36% and varied little with genotype, N rate, or cropping year. Biomass accumulation from similar N additions (AUE), however, was significantly higher for the selections than Russet Norkotah at 112 kg N ha-1 in 1997 only. At low N rate (112 kg ha-1), the selections had higher physiological use efficiency (PUE28) (mean 45.9 g g1) than Russet Norkotah (25.9 g g1). Results from this study demonstrate that, although N recovery was similar for the four genotypes, the Texas Norkotah strains produced greater biomass than Russet Norkotah per kg N applied at low rate in 1997 and per kg of fertilizer N absorbed by the plant in both years. However, under the conditions of this study, higher biomass of the selections did not translate into a marketable yield advantage over the standard cultivar.ResumenEl poco vigor del follaje y los altos requerimientos de N de “Russet Norkotah” pueden conducir a una pérdida de N y a contaminación por agua subterránea en suelos de textura gruesa. Recientes selecciones clonales de Texas han producido razas con un follaje más numeroso y vigoroso, el cual puede alterar los requerimientos de N. Durante dos años de estudios se examinó la eficiencia en el uso de N (EUN), los rendimientos y la calidad de la selección de razas de Russet Norkotah fertilizadas con diferentes niveles de N en un suelo franco arenoso de Hubbard en Minnesota central. Las selecciones, Texas Norkotah Strain (TXNS) 112, TXNS 223, y TXNS 278, crecieron con Russet Norkotah estándar bajo condiciones de irrigación y recibieron niveles totales de N de 28, 112, 224 o 336 kg ha-1. Los rendimientos comerciales totales y el largo (>340 g) de los tubérculos se incrementó linealmente (P<0.05) con las tasas de N aplicadas en 1998 pero no con las de 1997. El efecto princpipal en el genotipo no fue significativo en ninguno de los parámetros de rendimiento del tubérculo medidos en base al peso en fresco. Los rendimientos totales de follaje, tubérculo y biomasa seca fueron 116%, 5.8% y 13.2% respectivamente, más altos que las selecciones de Russet Norkotah. El índice de cosecha (IC), o la proporción de cantidad total de materia seca dividida entre los tubérculos fue 7% mayor para Russet Norkotah que para las selecciones TXNS, reflejando el mayor crecimiento de follaje de las selecciones. Las selecciones acumularon N en cantidad significativamente mayor en los follajes (0.113 kg kg-1 N) que en el clon estándar (0.053 kg kg-1 N) a medida que la tasa de N fue incrementándose de 28 a 336 kg ha-1, y la diferencia entre las selecciones y el clon estándar fue más grande a tasas más altas de N que a bajas tasas de N. Russet Norkotah repartió 10% más N a los tubérculos que las selecciones TXNS, reflejando la diferencia en el IC entre el cultivar estándar y sus clones. El nitrógeno recuperado del fertilizante de N aplicado en adición a los 28 kg ha-1 iniciales de N (EUN28) promedió 36% y varió en pequeña cantidad con genotipo, tasa de N o año agrícola. La acumulación de biomasa de adiciones similares de N (EAN) fue, sin embargo, significativamente mayor en el caso de las selecciones que en Russet Norkotah a 112 kg N ha-1 solamente en 1997. A bajas tasas de N (112 kg ha-1), las selecciones presentaron mayor eficiencia fisiológica de uso (EFU28) (lo que significa 45.9 g g-1) que la Russet Norkotah (25.9 g g-1). Los resultados de este estudio demuestran que, aunque la recuperación de N fue similar en los 4 genotipos, la raza Texas Norkotah prodigo una mayor biomasa que Russet Norkotah por Kg N aplicado a bajas tasas en 1997 y por kg de fertilizante de N absorbido por la planta en ambos años. Sin embargo, bajo las condiciones de este estudio, una mayor biomasa de las selecciones no se tradujo en un rendimiento comercial más ventajoso sobre el cultivar estándar.

Nutrient cycling in the vegetable processing industry: Utilization of potato by-products

Potato (Solanum tuberosum) production in Canada and the United States totals approximately 30 × 106 Mg yr-1. Approximately half of this is unsuitable for human consumption. This potato by-product comprises cull potatoes and potato processing waste (PPW). Liquid waste from processing plants can be applied to agricultural land. With strict environmental monitoring and control, crops such as corn (Zea mays L.), vegetables and grass can be used to divert large volumes of liquid waste. Solid waste and culls have traditionally been put in landfills or disposed of on agricultural land as a fertilizer. However these can be diverted from landfill sites or agricultural land and used as a high-quality animal feed, principally in beef feedlots. Research has shown that PPW can replace corn and barley (Hordeum vulgare L.) grain without negative effects on growth of beef cattle or meat quality. Indeed, efficiency of animal growth per unit diet intake is improved. These effects have been observed with diets containing up...

Assessment of water quality trends in the Minnesota River using non-parametric and parametric methods.

Excessive loading of sediment and nutrients to rivers is a major problem in many parts of the United States. In this study, we tested the non-parametric Seasonal Kendall (SEAKEN) trend model and the parametric USGS Quality of Water trend program (QWTREND) to quantify trends in water quality of the Minnesota River at Fort Snelling from 1976 to 2003. Both methods indicated decreasing trends in flow-adjusted concentrations of total suspended solids (TSS), total phosphorus (TP), and orthophosphorus (OP) and a generally increasing trend in flow-adjusted nitrate plus nitrite-nitrogen (NO(3)-N) concentration. The SEAKEN results were strongly influenced by the length of the record as well as extreme years (dry or wet) earlier in the record. The QWTREND results, though influenced somewhat by the same factors, were more stable. The magnitudes of trends between the two methods were somewhat different and appeared to be associated with conceptual differences between the flow-adjustment processes used and with data processing methods. The decreasing trends in TSS, TP, and OP concentrations are likely related to conservation measures implemented in the basin. However, dilution effects from wet climate or additional tile drainage cannot be ruled out. The increasing trend in NO(3)-N concentrations was likely due to increased drainage in the basin. Since the Minnesota River is the main source of sediments to the Mississippi River, this study also addressed the rapid filling of Lake Pepin on the Mississippi River and found the likely cause to be increased flow due to recent wet climate in the region.

Evaluation of manure-derived struvite as a phosphorus source for canola

Ackerman, J. N., Zvomuya, F., Cicek, N. and Flaten, D. 2013. Evaluation of manure-derived struvite as a phosphorus source for canola. Can. J. Plant Sci. 93: 419-424. There is growing interest in the treatment of swine manure to mitigate water quality issues related to phosphorus (P) from livestock operations. Precipitation of P as struvite (MgNH4PO4·6H2O) is a potential strategy to achieve this. The overall objective of this growth room study was to evaluate the effect of manure-derived struvite (MDS) on canola growth and P recovery efficiency. Pure struvite (PS), monoammonium phosphate (MAP), and polymer-coated monoammonium phosphate (PCMAP) were applied to canola plants in plastic pots containing 2 kg of a sandy loam soil. Biomass yields for MDS and PS were similar at all P rates (mean = 7.6 g pot-1) and significantly smaller than those for MAP and PCMAP (mean = 9.3 g pot-1). Differences in P uptake among P sources were detected at the highest P rate where P uptake was significantly greater for MAP and PCMAP (mean = 22.7 mg P pot-1) than for the struvite forms (mean = 16.4 mg P pot-1). Our results show that although P uptake was similar for the struvites and commercial fertilizers at P2O5 rates of 38 mg pot-1 or lower, biomass yield per unit of P taken up was smaller for the struvites. This may be due to lower initial solubility of the struvites in the alkaline (pH 7.7) soil used in this experiment, which gave an early stage growth advantage to canola fertilized with MAP and PCMAP. These results suggest that it may be necessary to supplement struvite with soluble P fertilizers, such as MAP, if applied on soils such as that tested in this study.

Targeted 16S rRNA high‐throughput sequencing to characterize microbial communities during composting of livestock mortalities

A comprehensive understanding of the microbial community is necessary to ensure a significant reduction in pathogens during the composting process.

Phosphorus Mobilization from Manure-Amended and Unamended Alkaline Soils to Overlying Water during Simulated Flooding

Anaerobic soil conditions resulting from flooding often enhance release of phosphorus (P) to overlying water. Enhanced P release is well documented for flooded acidic soils; however, there is little information for flooded alkaline soils. We examined the effect of flooding and anaerobic conditions on P mobilization using 12 alkaline soils from Manitoba that were either unamended or amended with solid cattle manure. Pore water and floodwater were analyzed over 8 wk of simulated flooding for dissolved reactive P (DRP), Ca, Mg, Fe, and Mn. As expected, manured soils had significantly greater pore and floodwater DRP concentrations than unamended. Flooding increased pore water DRP concentrations significantly in all soils and treatments except one manured clay in which concentrations increased initially and then decreased. Floodwater DRP concentrations increased significantly by two- to 15-fold in 10 soils regardless of amendment treatment but remained relatively stable in the two soils with greatest clay content. Phosphorus release at the onset of flooding was associated with the release of Ca, Mg, and Mn, suggesting that P release may be controlled by the dissolution of Mg and Ca phosphates and reductive dissolution of Mn phosphates. Thereafter, P release was associated with release of Fe, suggesting the reductive dissolution of Fe phosphates. Differences in pore water and floodwater DRP concentrations among soils and amendment treatments and the high variability in P mobilization from pore water to floodwater among soils indicate the need to further investigate chemical reactions responsible for P release and mobility under anaerobic conditions.

Impact of manure phosphorus fractions on phosphorus loss from manured soils after incubation.

The risk of P loss from manured soils is more related to P fractions than total P concentration in manure. This study examined the impact of manure P fractions on P losses from liquid swine manure- (LSM), solid cattle manure- (SCM), and monoammonium phosphate- (MAP) treated soils. Manure or fertilizer was applied at 50 mg P kg soil, mixed, and incubated at 20°C for 6 wk to simulate the interaction between applied P and soil when P is applied well in advance of a high risk period for runoff. Phosphorus fractions in manure were determined using the modified Hedley fractionation scheme. We used simulated rainfall (75 mm h⁻¹ for 1 h) to quantify P losses in runoff from two soils (sand and clay loam). The proportion of total labile P (total P in water+NaHCO fractions) in manure was significantly greater in LSM (70%) than SCM (44%). Mean dissolved reactive P (DRP) load in runoff over 60 min was greatest from MAP-treated soil (18.1 mg tray⁻¹), followed by LSM- (14.0 mg tray⁻¹) and SCM- (11.0 mg tray⁻¹) treated soils, all of which were greater than mean DRP load from the check (5.2 mg tray⁻¹). Total labile P (water+NaHCO) in manure was a more accurate predictor of runoff DRP loads than water extractable P, alone, for these two soils. Therefore, NaHCO extraction of manure P may be a useful tool for managing the risk of manure P runoff losses when manure is applied outside a high risk period for runoff loss.

Topsoil replacement depth and organic amendment effects on plant nutrient uptake from reclaimed natural gas wellsites

Sustained plant nutrient a vailability on reclaimed wellsites is critical to the successful restoration of crop productivity. This study evaluated topsoil replacement depth (TRD) (0, 50, 100, and 150% of mandatory TRD) and organic amendment [beef cattle feedlot manure, compost derived from straw-bedded cattle feedlot manure, wheat (Triticum aestivumL.) straw, alfalfa (Medicago sativaL.) hay, and unamended control] effects on nutrient uptake by a wheat crop at three abandoned gas wellsites in south-central Alberta. Grain N uptake increased by 0.055 kg ha-1 for each percent increase in TRD, reflecting the corresponding linear increase in grain N concentration. Low carbon to nitrogen (C:N) ratio amendments, particularly compost and alfalfa, were the most effective for improving grain N concentration and uptake. Conversely, N concentration and uptake were lowest for the high C:N (53:1) wheat straw amendment. Reclamation programs should, therefore, consider incorporation of the low C:N alfalfa or compost in or...

Dissipation of Antimicrobials in Feedlot Manure Compost after Oral Administration versus Fortification after Excretion

Fortification of manure with antimicrobials is one approach to studying their dissipation. However, fortified antimicrobials may not accurately model dissipation that occurs after antimicrobials have been administered to livestock in feed and excreted in manure. This study examined the dissipation of antimicrobials excreted in manure versus those added directly to manure (fortified). Steers were fed a diet containing (kg feed) (i) 44 mg chlortetracycline, (ii) 44 mg each of chlortetracycline and sulfamethazine, (iii) 11 mg tylosin, and (iv) no antimicrobials (control). Fortified antimicrobial treatments were prepared by adding antimicrobials to control manure. Manure was composted for 30 d, sampled every 2 to 3 d, and analyzed for antimicrobials and compost properties. Antimicrobial dissipation followed first-order kinetics. The dissipation rate constant was significantly greater (based on 95% confidence limit) for excreted (0.29-0.54 d) than for fortified chlortetracycline (0.11-0.13 d). In contrast, dissipation rate constants were significantly greater for fortified sulfamethazine (0.47 d) and tylosin (0.31 d) than when the same antimicrobials were excreted (0.08 and 0.07 d, respectively). On average, 85 to 99% of the initial antimicrobial concentrations in manure were dissipated after 30 d of composting. The degree of dissipation was greater ( < 0.0001) for fortified (99%) than for excreted tylosin (85%). Composting can be used to reduce environmental loading of antimicrobials before field application of beef cattle manure. Dissipation rates of fortified antimicrobials during manure composting may not accurately reflect those of antimicrobials that are consumed and excreted by cattle.