Author: Stephanie Ann Nummer Publisher: ISBN: Category : Agricultural conservation Languages : en Pages : 79
Book Description
Nitrogen and phosphorus runoff from agricultural lands and the subsequent impact on water quality has been of great concern in the United States, due to harmful algal blooms and anoxic zones in areas such as Lake Erie and the Gulf of Mexico. Conservation practices have been widely used to reduce the quantity of nutrients leaving a field, but there is a lack of research on the effectiveness of these practices using field scale data. The objective of this thesis is to quantify the effect of conservation practices on nitrogen and phosphorus runoff in farmlands. A meta-analysis was conducted using the Measured Annual Nutrient loads from AGricultural Environments (MANAGE) database created by the USDA-ARS. MANAGE is a compilation of 65 publications including data on nitrogen and phosphorus loads, runoff, land use, fertilizer application, and other field characteristics. The observational nature of the dataset makes direct comparisons from field to field impossible because of large variations in field characteristics. Thus, additional steps must be taken to estimate the effect of conservation practices on nutrient loss. To quantify this effect, I used propensity score matching and multilevel modeling, two statistical methods common for observational data. Propensity score matching shows that conservation practices have a significant reduction of 67.5% in total phosphorus, 83% in particulate phosphorus, and 67.3% in particulate nitrogen. Multilevel modeling results - calculated using two different computational methods - support these findings by showing a significant reduction of 57.7% in total phosphorus, 76.2% and 82.1% in particulate phosphorus (via the two methods), and 63.7% in particulate nitrogen. When examining different land uses and fertilizer application methods, the multilevel modeling showed that conservation practices had the most impact on row crops (e.g. corn and soybeans) and on farms fertilized via the injected or surfaced applied method. The results from this work represent the average effect of conservation practices on a national scale. At a regional scale, the effects of conservation practices may vary because of regional differences in agricultural practices and climate. To assist future research at regional and local scales, this thesis provides a Bayesian modeling framework for future quantification of these effects.
Author: Thomas Kevin O'Donnell Publisher: ISBN: Category : Agricultural conservation Languages : en Pages : 344
Book Description
The U.S. Department of Agriculture initiated the Conservation Effects Assessment Project in 2003 to quantify water quality and wildlife benefits of conservation programs funded by the 2002 Farm Security and Rural Investment Act. This study examined the effects of agricultural best management practices (BMPs) implemented in the Goodwater Creek Experimental Watershed (GCEW) and investigated strategies to target future BMPs. Evaluation of storm events between 1993 and 2006 showed no significant BMP effects on dissolved atrazine and NO3-N losses after 14% of the GCEW had been affected by BMP establishment. Approximately 20 and 4 years of monitoring will be needed before a statistically significant ([alpha]=0.05) 25% reduction in mean dissolved atrazine and nitrate-N can be demonstrated at the GCEW outlet, respectively. A widely used hydrologic model, SWAT, identified fields adjacent to streams with lesser depths to the argillic horizon as the highest risk for atrazine and NO3-N pollutant loss. Twenty two percent and 34% of cropped fields in the GCEW required establishment of vegetative filter strips to reduce dissolved atrazine and NO3-N loads by 25% at the GCEW based on SWAT predictions. A 99% accurate method to quantify soil redoximorphic features (SRFs) was developed using a digital camera and image classification software. Correlation between quantified SRFs and the topographic wetness index was found for one of two GCEW fields, indicating field soil surveys may serve as relatively quick reconnaissance methods to identify sensitive field areas.
Author: Rishi Prasad Publisher: ISBN: Category : Languages : en Pages : 222
Book Description
Field (or farm) in plant part, represented 72, 84, and 89% of total N uptake and 89, 90 and 93% of total P uptake for potato, sweet corn and silage corn, respectively. Nitrogen left in the field in crop residues was greatest for potato and posed potential for N losses due to the fast decomposition of potato residues after vine desiccation. Use of a potato model indicated excess water above the crop ET, higher fertilizer applications than the university recommended rates and poor synchrony between plant N uptake and fertilizer application timing were responsible for leaching loss of N.
Author: Ashani Thilakarathne Publisher: ISBN: Category : Agricultural systems Languages : en Pages : 0
Book Description
Corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production in Illinois has a significant impact on the economy and environmental footprint in the state and the Midwest region. Nutrient leaching from Midwestern agricultural fields is one of the major reasons for the hypoxic zone developed in the Gulf of Mexico. Winter-fallow and early spring (after fertilizer application) are the two most critical periods for nutrient leaching due to increased precipitation and availability of nutrients. Cover crops (CCs) in these seasons are a promising best management practice (BMP) to reduce nutrient leaching in the winter-fallow season. No-till (NT) and reduced tillage (RT) are some other BMPs that farmers in Illinois adopt to reduce erosion. The adoption of CCs is limited due to the lack of knowledge and data on the yield and environmental benefits of CCs in different climatic and soil regimes. Thereby, this doctoral dissertation addresses several critical questions about CC and tillage impacts in claypan soils of southern Illinois with four principal projects with multiple objectives. Research study 1 was a field experiment conducted from 2013-to 2021 to understand the effect of CCs (CCs vs. noCC) and two tillage (NT and RT) practices on soil nitrate-N leaching. The experimental design was a complete randomized design with CC treatments that had two levels (two crop rotations) corn-cereal rye (Secale cereale L.)-soybean-hairy vetch (Vicia villosa R.) [CcrShv] and corn-noCC-soybean-noCC [CncSnc] and tillage treatments with two levels (NT and RT) replicated three times in the field. Each plot had a pan lysimeter installed below the A horizon (22-30 cm depth) to collect water samples weekly or biweekly depending on the rainfall. The corn yield was significantly greater in RT rotations compared to NT rotations with a 36% increase in the yield in 2019 and 2021 corn rotations. The yield was significantly greater in CcrShv rotations compared to the CncSnc rotations. The greatest yield was observed in the interaction of CcrShv-RT in all years. This increase in yield is inversely correlated to the remaining soil N values when the N credit from CCs was not accounted for. Soil nitrate-N leaching was significantly greater in CcrShv rotations compared to the CncSnc rotation in 2021 indicating vetch CC biomass decomposition can lead to increased leaching losses if the window between CC termination and corn planting is not minimized. Precipitation during the early spring can play a vital role in flushing the newly applied fertilizer as well as the N released from decomposing CC residue. The excessively wet year of 2019 showed that N losses are dominated by both nitrate-N leaching and nitrous oxide emissions, but in a typical growing season N losses are dominated by leaching compared to emissions. Research study 2 was designed to better understand the N cycling and fate of applied N in a complete corn-soybean rotation in southern Illinois with CCs and tillage practices. The research was overlayed in the same field with the same crop rotation and tillage practices. In this study, 15N labeled urea fertilizer (9.2% atom) was applied before the corn and soybean seasons. Soil, water, and biomass samples were collected to understand N distribution in each pool. In the corn season in 2017 a significantly greater 15N recovery was observed in CC (CcrShv) plots compared to the noCC plots in the sample collected seven days after planting (DAP). In the CC and depth interaction, a significantly greater 15N recovery was observed in 15-30 cm depth showing that the increased macropores due to CCs can lead to subsurface movement of N through the topsoil. The 15N recovery in water samples was high in CncSnc rotations in the cereal rye season but was significantly greater in CcrShv rotations (8.95 kg ha-1) in hairy vetch seasons. In the two years of complete rotation, the cumulative 15N recovery (quantity derived from fertilizer in water) was significantly greater in CC rotation. In the corn plants, the 15N recovered from the soil was greater than the 15N recovered from fertilizer. This shows the importance of the residual N from prior fertilizer and organic matter input. In the cereal rye season, CCs recovered significantly greater 15N from fertilizer compared to noCC rotations, assuring that cereal rye is an effective nutrient scavenger. A similar pattern was observed in the hairy vetch season as well. However, the soybean 15N recovery was greater in noCC rotations compared to CC rotations. The third study was a field trial on CCs and tillage to understand their individual and combined impact on soil physical parameters. Soil physical parameters were first measured in 2014 and were repeated in 2021. Bulk density at the 0-5 cm depth was 5% lower in 2021 compared to 2014 with the lowest BD in CC rotations with RT practices. For the depth of 0-15 cm, the lowest BD was observed in CC rotation with RT but, the largest reduction was observed in the CC rotation with NT. The wet aggregate stability was improved from 15-28 % over the years in all rotations. The lowest percentage improvement was observed in noCC rotation with RT practice. Penetration resistance was significantly lower in CC plots for the depth of 0-2.5 cm. CCs further improved the time to runoff in plots even though the infiltration rates were not affected. Chemical soil health indices were not significant overtime for CCs or tillage practices. However, a large number of earthworm counts were observed in NT systems compared to RT systems. The final project was a field trial to identify the soil P response to the CC and tillage practices. For this study, three different CC rotations, [corn-cereal rye-soybean-hairy vetch / corn-cereal rye-soybean-oats+radish / corn-noCC-soybean-noCC] and two tillage practices (NT and RT) were used. Soil samples were collected after the corn harvest in 2015 and 2021 and were analyzed for soil Phosphorus (P), inorganic P fractions by Chan and Jackson method, and dissolved reactive phosphorus (DRP) in leachate. The soil Mehlich-3 and Bray-1 P values indicate a great concentration of P in 0-15 cm depth for both years. More refined sampling in 2021 showed that the majority of P in 0-15 cm depth concentrates at the near-surface soil, in 0-5 cm depth irrespective of the CC and tillage treatment. Inorganic soil P fractions were not significantly different between CCs or tillage practices over time. Yet, irrespective of the treatment the non- labile P forms increased in 2021in the soil compared to 2015. The average and cumulative DRP values were highly dependent on the precipitation amounts and timing. However, in general, NT systems had greater average and cumulative DRP leaching compared to RT in both years. In general, CCs in the winter-fallow season is a good recommendation for farms that seek to maximize their production with a minimal environmental footprint. In the long run, CCs can improve soil physical and chemical properties which ultimately can increase the yield potential for corn and soybean. The added benefit of N credit due to leguminous CCs can reduce the fertilizer inputs. The CC benefits including the reduction in nutrient leaching depend on the type of CCs used in the field. More importantly, the CC termination time will be critical to obtain the maximum benefit of CCs. Even though the NT practices improve soil physical properties, long-term NT can increase the risk of soil P stratification in near-surface soils and can ultimately lead to more P loss via erosion, runoff, and soil water leaching. However, the combined use of CC and NT practices can help minimize the potential for erosion and runoff.
Author: Stephanie Ann Nummer
Author: Gary S. Johnson
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Author: Thomas Kevin O'Donnell
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Author: Rishi Prasad
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Author: Ashani Thilakarathne