Organic Nitrogen Fertilizer Selection Influences Water Use Efficiency in Drip-Irrigated Sweet Corn

Project Director: Arina Sukor, University Putra Malaysia

Project Overview

Supplementing field crops with nitrogen (N) mid-season is a common practice for optimizing growth and yield. There are a variety of organic N sources available for farmers to choose from, so understanding the differences in crop responses to individual fertilizers is crucial. One characteristic that can be influenced by fertilizer type is water use efficiency (WUE), which is a measure of how efficiently a crop utilizes input water to generate useful output. Previous studies have revealed correlations between water use efficiency, phytohormones (organic compounds, including salicylic acid and auxin, that can regulate plant growth and development), and micronutrients (such as iron and zinc).

This study assessed the impacts of four organic N fertilizers (fish emulsion, cyanofertilizer, blood meal, and feather meal) – each of which had different phytohormone and micronutrient contents – on the water use efficiency and leaf gas exchange components of drip-irrigated sweet corn in Colorado.

Farmer Takeaways

Cyanofertilizer, a liquid fertilizer that utilizes N-fixing bacteria and can be produced on-farm, may be a promising option for supplying sweet corn with mid-season N and enhancing fresh ear yields over consecutive growing seasons.
Cyanofertilizer’s high salicylic acid content may contribute to its ability to improve water use efficiency in sweet corn, which is especially important for producers in water-limited or drought-susceptible regions.

Project Objectives and Approach

To evaluate the impacts of organic N fertilizer type, phytohormone content, and micronutrient content on the water use efficiency (WUE) and yield of sweet corn

Field experiments were conducted on certified organic land at the Colorado State University Horticulture Field Research Center. Treatments included: (1) no-fertilizer control, (2) liquid fish emulsion fertilizer, (3) liquid cyano-fertilizer, (4) solid blood meal fertilizer, and (5) solid feather meal fertilizer. Fertilizer samples were analyzed for N, C, P, K, Fe, Ca, Mg, Zn, and phytohormone content.
Sweet corn was seeded and irrigated daily (steady flow rate for a set amount of time) via an automated drip irrigation system. Precipitation data was collected and added to irrigation water data to calculate total amounts of water applied over the growing season.
- - Both liquid fertilizers (fish emulsion, cyano-fertilizer) were supplied in four applications through the drip irrigation system over the growing season, while both solid fertilizers (blood meal, feather meal) were incorporated into the soil prior to planting. All fertilizers were applied at equivalent N rates (112 kg N/ha).
Leaf gas exchange measurements were taken from three plants per plot during tasseling*.
- - *Tasseling: the stage of growth in corn when the tassel, or male flower, emerges from the top of the plant. This process marks the transition from vegetative to reproductive growth.
Plants from each treatment were harvested 79 days after seeding, and data was collected on marketable yields (fresh sweet corn ear weights) and total aboveground biomass. Field water use efficiency (fWUE)* and instantaneous water use** efficiency (iWUE) were calculated.
- - *Field water use efficiency: fresh sweet corn ear yield divided by total amount of water applied over the growing season (precipitation + irrigation + fertigation)
  - **Instantaneous water use efficiency: the ratio of net photosynthetic rate to transpiration rate. iWUE is useful for understanding how a plant responds to its immediate environment, including light, temperature, humidity, drought, etc.

Key Findings

Sweet corn yields varied by year and were influenced by N fertilizer type, with cyanofertilizer performing the best over both growing seasons

In Year 1, all fertilizer treatments significantly increased sweet corn yield compared to the unfertilized control, but in Year 2, only the cyanofertilizer treatment had a significantly higher yield. Fresh yields for the cyanofertilizer treatment were consistently high across both growing seasons (~1500 kg/ha Year 1, ~1900 kg/ha Year 2), indicating that cyanofertilizer may be a more suitable option for mid-season N fertilization over consecutive growing seasons than other organic N fertilizers.
- - In Year 1, fresh sweet corn yields were significantly higher in the cyanofertilizer and fish emulsion treatments than in the blood meal and feather meal treatments, suggesting that liquid fertilizers may perform better than solid fertilizers during the first growing season.

Cyanofertilizer may improve water use efficiency (both field and instantaneous) in sweet corn, outperforming other organic fertilizer types; however, longer-term studies are needed

In Year 1, the fish emulsion, cyanofertilizer, and blood meal treatments had significantly higher fWUEs compared to the unfertilized control, but in Year 2, there were no statistical differences between the treatments and control. These findings in Year 2 were largely due to an increase in fWUE in the unfertilized Control between Years 1 and 2, rather than a decrease in fWUEs among the fertilizer treatments.
- - Across both years, fWUE for the cyanofertilizer treatment was numerically higher (~40 kg fresh ear yield/cm water applied Year 1, ~45 kg/cm Year 2) than the other fertilizer treatments and control, indicating that cyanofertilizer may be an advantageous option for maintaining high water efficiency in sweet corn. This could be particularly beneficial for farmers producing sweet corn in water-limited regions.
The cyanofertilizer treatment had a significantly higher instantaneous water use efficiency (iWUE) than all other treatments and the unfertilized control, suggesting that cyanofertilizer may be a viable option for maintaining high water efficiency in sweet corn across diverse growing conditions, and may enhance crop resiliency.
Transpiration rate (rate of water loss to the atmosphere) for the cyanofertilizer and fish emulsion treatments were significantly lower than for the blood meal treatment and unfertilized control, but net photosynthetic rates were statistically identical, providing further evidence that cyanofertilizer can improve water retention without reducing photosynthetic activity.

Salicylic acid, a phytohormone, may enhance sweet corn ear yield and water use efficiency (field and instantaneous)

Sweet corn yield, iWUE, and fWUE were positively correlated with the amount of salicylic acid applied in organic N fertilizers. Of the four N fertilizers applied, cyanofertilizer had the highest salicylic acid content. This study provides evidence of the importance of salicylic acid (and phytohormones) in crop production.

Resources

Sukor, A., Qian, Y., & Davis, J. G. (2023). Organic Nitrogen Fertilizer Selection Influences Water Use Efficiency in Drip-Irrigated Sweet Corn. Agriculture, 13(5), 923.

Location

Colorado

Collaborators

Yaling Qian, Colorado State University
Jessica Davis, Colorado State University

Region

Plains

Topic

Soil Health, Crop Nutrient Management

Year Published

2023