Effects of cyanobacterial fertilizers compared to commonly-used organic fertilizers on nitrogen availability, lettuce growth, and nitrogen use efficiency on different soil textures
Date
2013
Authors
Sukor, Arina, author
Davis, Jessica, advisor
Stonaker, Frank, committee member
Storteboom, Heather, committee member
Stromberger, Mary, committee member
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Abstract
Nitrogen plays a crucial role in synthesis of amino acids and proteins, plant growth, chlorophyll formation, leaf photosynthesis, and yield development of lettuce. Generally, organic farmers use composted manure, legume cover crops, and off-farm fertilizers such as fish emulsion to meet the nitrogen (N) demand of crops. However, the nutrient composition of off-farm fertilizers such as composted manure and fish emulsion varies widely depending on animal species and often have higher transportation costs. Therefore, an evaluation of the application of cyanobacteria in comparison to the commonly-used organic fertilizers was conducted as an alternative potential N biofertilizer. The laboratory soil incubation and greenhouse studies were conducted to evaluate the effect of N availability from potentially mineralizable N on different types of soil textures. Then, a greenhouse study was conducted to assess the effect of N availability from cyanobacterial fertilizers compared to the commonly-used organic fertilizers on lettuce growth, fertilizer recovery and lettuce root response on N use efficiency. Lettuce (Lactuca sativa) is a shallow-rooted crop and requires an extensive amount of N fertilizer to produce yield. The aims of the soil incubation study were to determine the rates of mineralization for different organic fertilizers, influence of soil texture on N mineralization, and to evaluate changes in soil microbial biomass from fertilizer application to sandy and clayey soils. In this study, N mineralization potential of cyanobacterial fertilizers were compared with traditional organic fertilizers in two soils with contrasting textures in a laboratory incubation study at constant temperature (25 degrees C) and moisture content (60% water-filled pore space) for 140 days. Soils were destructively sampled over the course of 140 days and analyzed for NH4+-N, and NO3--N, soil microbial biomass C, soil organic C, and soil total C and N. In both soils, soil NH4+-N was the highest at day 56 and decreased from day 56 to 140 due to its conversion to soil NO3--N. Compost treatment significantly increased soil microbial biomass C (207.5 mg C kg-1 soil) compared to fish emulsion (115.42 mg C kg-1 soil) in sandy soil. The N availability was 9% greater from fish emulsion than liquid cyanobacteria, and 6% greater from solid cyanobacteria than compost in sandy soil. The fish emulsion treatment showed 5% higher N availability compared to the solid and liquid cyanobacterial fertilizers. In the greenhouse study, percentage fertilizer recovery (PFR) was quantified to assess the efficiency of N uptake by lettuce to produce yield. A greenhouse study was conducted for 63 days to evaluate cyanobacterial and traditional organic fertilizers application on lettuce N response. Total leaf area, fresh yield, leaf dry weight, and leaf total N content were measured at the end of the greenhouse study. Total N uptake in lettuce tissue and PFR were calculated based on the analyses results. Soil applied fish emulsion recorded significantly higher fresh yield at 112 kg N ha-1 (147 g) compared to 56 kg N ha-1 (117 g) in clayey soil relative to sandy soil. Soil-applied liquid cyanobacteria recorded significantly higher yield compared to composted manure by 58%. Solid cyanobacteria recorded significantly higher total N uptake at 56 kg N ha-1 compared to 112 kg N ha-1 in clayey soil. In conclusion, soil applied fish emulsion treatment recorded higher PFR (99%) than soil applied composted manure (44%) at 56 kg N ha-1 on clayey soil. Soil applied fish emulsion has significantly higher PFR (57%) compared to the combination soil and foliar fertilizer (FFCom and FLScyb) at 56 kg N ha-1 in sandy soil. Nitrogen is also acquired from the soil by the plant roots. In the greenhouse study, root response to N fertilization was assessed to determine the efficiency of N uptake by lettuce to produce yield. A greenhouse study was conducted for 63 days to evaluate cyanobacterial and traditional organic fertilizers application on lettuce root response. Root: shoot ratio, root dry weight, root surface area, and root length density were measured at the end of the greenhouse study. Nitrogen use efficiency (NUE) was calculated based on the analyses results. There was no significant difference observed in root dry weight. The composted manure (Com) treatment recorded significantly higher root: shoot ratio at 56 kg N ha-1 while foliar and soil applied liquid cyanobacteria (FLScyb) treatment recorded lower root: shoot ratio at 112 kg N ha-1. The foliar applied fish emulsion and soil applied composted manure (FFCom) treatment recorded the highest root surface area compared to other treatments at 112 kg N ha-1 on clayey soil . The FLScyb treatment recorded higher root surface area compared to the Com treatment at 112 kg N ha-1 on sandy soil. The fish emulsion (Fish) treatment recorded higher root length density at 112 kg N ha-1 on clayey soil while FLSCyb recorded higher root length density on sandy soil at 112 kg N ha-1 compared to the Fish and solid cyanobacteria (Scyb) treatments. In conclusion, the Fish treatment recorded 35 % higher NUE at 56 kg N ha-1 on clayey soil while Scyb treatment has significantly 24% higher NUE compared to Com treatment at 56 kg N ha-1 in sandy soil. Overall, the soil applied fish emulsion treatment recorded higher percentage fertilizer recovery and NUE compared to the solid and liquid cyanobacterial fertilizers at 56 kg N ha-1 on clayey soil. However, the combined soil and foliar cyanobacterial fertilizer and soil applied solid and liquid cyanobacterial fertilizers recorded higher percentage fertilizer recovery and NUE at 56 kg N ha-1 compared to the composted manure which correspond to lettuce yield component which was higher in fish emulsion compared to the composted manure.
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Subject
lettuce
nitrogen
nitrogen availability
nitrogen use efficiency
organic fertilizers
soil texture