Agroecosystem and cycling loops are open when considering the reutilization of inputs in farming areas. Non-renewable resources have been transformed or relocated from the air, water and land into the system and are flowing out as wastes rather than reusable, recyclable resources. Therefore, current trends in agriculture have moved towards more sustainable cultivation systems with higher efficiency of input use, since mineral nutrient losses due to runoff, leaching, erosion and gas emissions are leading to environmental degradation. A huge variety of materials can serve as a crop nutrient supply and they can be derived from different resources. The integrated plant nutrition system (IPNS) thrives tailoring plant nutrition and soil fertility management, taking advantage of the conjunctive and harmonious use of inorganic, organic and biological resources. We hypothesize that the synergetic effects of the combination of humic acid HA + biofertilizer will improve plant agronomic outcomes when comparing the application of each product alone. We initiated this project conducting a greenhouse study and field experiments evaluating the effects of an IPNS on corn. Posteriorly, the positive results in terms of corn biomass increasing, led to another greenhouse study addressing cannabis (Cannabis sativa L.) due its valuable biomass as an end/selling product.
The greenhouse studies evaluated the effects of commercial synthetic fertilizer, HA, compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively, and their synergy on corn and cannabis early development under a period of water deficit stress. Generally, for both studies, when compared to the control values, the use of HA, biofertilizers and the integration of both substances generated significantly greater early season plant height, chlorophyll content and photosynthetic efficiency.
The three-year field trial investigated the effects of nitrogen (N) fertilizer, HA, compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively and their synergy on corn growth. The individual and integrated application of HA and biofertilizer generally influenced corn development, to varying degrees. In 2017, corn height, NDVI, greenness and vigor were sensitive to the application of these biostimulants in different magnitudes and growth stages, however grain yield and nutrient content were not affected. In combined studies from 2018 and 2019 corn height was not impacted by biostimulant application but NDVI, photosynthetic efficiency, greenness and vigor were affected at different doses and corn growth stages. Only one treatment integrating HA + biofertilizer led to increased grain yield.
In sum, these studies provided evidence that the individual and combined application of HA and biofertilizer can positively influence corn and cannabis growth most likely due to their plant biostimulant effects. However, the current study cannot conclusively affirm that the integrated use of HA and biofertilizers following the IPNS is a superior practice than the application of each compound individually and further studies should be conducted to validate these findings. / Doctor of Philosophy / The status of the corn (Zea mays L.) demand in Virginia and the Mid-Atlantic region is currently in deficit regarding the production in this area. This demand is exceeding supply by approximately 150%, then increasing feed grain yield and consequently production in the region can be simultaneously beneficial to crop farmers, end-users and the entire food supply chain. Furthermore, the consumer market is becoming more aware about sustainable practices for food production, which encourages producers to adopt agricultural practices that can minimize negative environmental impacts. This scenario enforces the scientific community's responsibility to test and develop environmental-friendly methods able to increase fertilization efficiency, decreasing the use in synthetic inputs but maintaining yield. The integrated plant nutrition system (IPNS) implements the combined and harmonious use of inorganic, organic and biological resources to take advantage of the potential synergetic effects. We conducted greenhouse studies and field experiments evaluating the effects of an IPNS on corn, and posteriorly based on the preliminary results obtained with corn, a greenhouse study addressing cannabis (Cannabis sativa L.) was also carried out.
The greenhouse studies evaluated the effects of commercial synthetic fertilizer, humic acid (HA), compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively, and their synergy on corn and cannabis growth under a period of drought. Generally, for both studies, when comparing to the control values, the use of HA, biofertilizers and the integration of both compounds generated significantly greater early season plant height and photosynthesis measurements.
The three-year field trial investigated the effects of nitrogen (N) fertilizer, HA, compost/manure teas and bioinoculant as inorganic, organic and biological resources, respectively and their synergy on corn growth. The individual and combined application of HA and biofertilizer generally influenced corn development, to varying degrees. In 2017, corn height, vegetation index, greenness and vigor were sensitive to the application of these biostimulants in different magnitudes and growth stages, however grain yield and nutrient content were not affected. In combined studies from 2018 and 2019 corn height was not impacted by biostimulant application but vegetation index, photosynthetic efficiency, greenness and vigor were affected at different doses and corn growth stages. Only one treatment combining HA + biofertilizer led to increased grain yield.
In sum, these studies provided evidence that the individual and combined application of HA and biofertilizer can positively influence corn and cannabis growth most likely due their plant biostimulant effects. Even though, the current study cannot affirm that the combined use of HA and biofertilizers following the IPNS is a better practice than the application of each compound individually, this practice can be a more sustainable alternative to fit in the conventional farming scene.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/106703 |
| Date | 29 May 2020 |
| Creators | Da Cunha Leme Filho, Jose Franco |
| Contributors | Crop and Soil Environmental Sciences, Thomason, Wade E., Evanylo, Gregory K., Strickland, Michael, Zhang, Xunzhong |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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