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Organic nitrogen fertilizers influence nutritional value, water use efficiency, and nitrogen dynamics of drip irrigated lettuce and sweet corn

Date

2016

Authors

Sukor, Arina, author
Davis, Jessica G., advisor
Schipanski, Meagan E., committee member
Qian, Yaling, committee member
Argueso, Cristiana, committee member

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Abstract

Farmers usually rely on off-farm sources (fish emulsion, feather meal, blood meal) for the additional N needed during the growing season, and they are willing to pay the extra shipping cost. However, there is another fertilizer option being developed that could allow farmers to produce N on-farm, which is cyanobacteria, formerly known as the blue green algae. The general objectives of this study were to assess effects of organic N fertilizer application and N rates on nutritional value, water use efficiency, N dynamics of sweet corn and lettuce. A two-year field study was conducted in the summers of 2013 and 2014 at the Colorado State University Horticulture Research Center, Fort Collins, CO. The fertilizers used in this study were blood meal, feather meal, fish emulsion, and cyano-fertilizer. Both fish emulsion and cyano-fertilizer were supplied in four split applications over the growing season through drip irrigation, while the blood meal and feather meal were subsurface banded prior to planting. Lettuce and sweet corn were used as an indicator to evaluate effects of organic nitrogen (N) fertilizers on nutritional value, water use efficiency, and N dynamics. The aims of this study were to evaluate the effect of different types of organic N fertilizer on nutritional value; β-carotene, iron (Fe), zinc (Zn), marketable yield, water use efficiency (WUE), residual soil nitrate-N, N content, and N use efficiency (NUE) of horticultural crops, particularly lettuce and sweet corn. All fertilizer treatments in 2013 increased β-carotene concentration in leaf tissue compared to control, while only fish emulsion had a higher β-carotene concentration compared to other treatments in 2014. The high indole-3-acetic acid (IAA) applied in the fish emulsion treatment could have increased β- carotene concentration in lettuce in both years. Amount of IAA applied in the fish emulsion treatment was positively correlated with β-carotene concentration in both years. A significant negative correlation was found between marketable yield and β-carotene concentration in leaf tissue in 2014. High salicylic acid (SA) applied in the cyano-fertilizer treatment had a higher total leaf area compared to other fertilizers in both years. In lettuce, the blood meal treatment had a lower leaf Fe and Zn concentrations than other fertilizer treatments at 112 kg N ha-1. The cyano-fertilizer treatment had a higher leaf Fe concentration at 56 kg N ha-1. Leaf N concentration was positively correlated with Leaf Fe and Zn concentrations. Amount of NO3- -N applied in organic N fertilizers was negatively correlated with leaf Fe concentration. The cyano-fertilizer, fish emulsion, and blood meal treatments increased Fe concentration in sweet corn compared to feather meal. Amount of NO3- -N, Fe, and Zn applied in organic N fertilizers were positively correlated with kernel Fe concentration, while amount of NH4+ -N applied was negatively correlated with kernel Fe concentration. There was no N rate or treatment effect on leaf and kernel N concentrations in sweet corn. The amount of phytohormone, Ca, and Fe applied in organic N fertilizers may have affected field water use efficiency (fWUE), instantaneous water use efficiency (iWUE), kernel number, and leaf gas exchange components of sweet corn. Cyano-fertilizer apparently had a higher WUE, likely due to the high amount of SA applied. A positive relationship was observed between the amount of SA applied with iWUE and fWUE. The amount of Fe applied in organic N fertilizers had a positive correlation with leaf VPD and transpiration rate. The amount of Ca applied in the feather meal treatment may have contributed to increasing leaf temperature and decreasing net photosynthetic rate. The amount of NH4+ -N and Ca applied in the feather meal treatments were negatively correlated with both iWUE and fWUE. N rate effect was only observed in lettuce marketable yield and NUE in both years. Blood meal and feather meal fertilizers with higher percentage of N applied as NO3- -N compared to other fertilizer treatments had a higher residual soil NO3- -N concentration in 2013. Greater residual soil NO3 - -N was observed in the 0-30 cm depth compared to the 30-60 cm depth in 2014. Organic growers could achieve higher marketable yield and NUE when applying fertilizers at rates between 28 kg N ha-1 and 56 kg N ha-1 compared with 112 kg N ha-1. In sweet corn, the feather meal and fish emulsion treatments had a higher residual soil NO3- -N compared with other treatments. The fish emulsion, cyano-fertilizer, and blood meal had a higher leaf and kernel N contents and NUE compared with feather meal at 56 kg N ha-1. The cyanofertilizer treatment had a higher marketable ear yield and NUE compared with other treatments at 112 kg N ha-1 in 2014. The amount of C inputs and crop species may have affected soil permanganate oxidizable carbon (POXC) concentration in a single season study. Soil POXC concentration was higher in the cyanofertilizer treatment compared to the control treatment in sweet corn, while the opposite trend was found in lettuce. Depth effect was observed in soil POXC concentration at 0-30 cm compared to 30-60 cm in lettuce. Soil POXC concentration was higher at 112 kg N ha-1 compared to 56 kg N ha-1 in sweet corn, but there was no N rate effect in lettuce. Greater soil POXC concentration and marketable ear yield of sweet corn were observed in the cyano-fertilizer treatment compared to others at 112 kg N ha-1. Overall, our results indicate that organic N fertilizer, particularly cyano-fertilizer influenced soil POXC concentration over a short-term growing season of horticultural crops.

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