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Effects of Shallow Surface Ditches W...

Watkins, Mitchell Lee,

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Effects of Shallow Surface Ditches With Controlled Subsurface Tile Drainage on Drainage Flows, Nutrient Exports, and Crop Yields in Eastern North Carolina /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Effects of Shallow Surface Ditches With Controlled Subsurface Tile Drainage on Drainage Flows, Nutrient Exports, and Crop Yields in Eastern North Carolina // Mitchell Lee Watkins.
Author:	Watkins, Mitchell Lee,
Description:	1 electronic resource (143 pages)
Notes:	Source: Masters Abstracts International, Volume: 85-01.
Contained By:	Masters Abstracts International85-01.
Subject:	Copper. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30516294
ISBN:	9798379879129

Effects of Shallow Surface Ditches With Controlled Subsurface Tile Drainage on Drainage Flows, Nutrient Exports, and Crop Yields in Eastern North Carolina /
Watkins, Mitchell Lee,

Effects of Shallow Surface Ditches With Controlled Subsurface Tile Drainage on Drainage Flows, Nutrient Exports, and Crop Yields in Eastern North Carolina /Mitchell Lee Watkins. - 1 electronic resource (143 pages)

Source: Masters Abstracts International, Volume: 85-01.

Unrestricted conventional surface drainage ditches with subsurface tile (FD) are commonly used on the Eastern Seaboard to satisfy drainage needs. The large conventional FD ditches are efficient at drainage yet pose trafficability hazards, are direct pathways for nutrient export, and require the removal of valuable topsoil for installation. This thesis presents the findings of a field study that compared the FD ditches with small shallow ditches (SD) that utilize subsurface tile directed to a singular outlet equipped with a water management control structure capable of intense controlled drainage (CD).The conventional FD plots and SD had the same drain spacing for the surface ditches and subsurface tile, but the FD had uncontrolled outlets so no drainage management practice could be used. The SD system was installed with precision grade equipment so that ditches could be placed on an accurate grade and a precise surface crown could be placed between ditches. The shallow ditches were installed to a maximum depth of 30 cm.Crop yields were evaluated over nine crop seasons under a corn and soybean rotation. The SD system significantly increased yields in eight of nine seasons with an average increase of 0.4 Mg/ha (4%) over five years for corn and 0.5 Mg/ha (14.3%) increase over four years for soybeans.Outflows from the drainage systems were monitored for a 20 month period to determine the impact on drainage flow and nutrient export. The SD plots significantly decreased drainage (p=0.0001) over the study period by 48%. The SD treatment also decreased nitrate-N (NO3 - -N) concentrations found in the drainage water and the export of both NO3 - -N and total suspended solids (TSS). The SD ditches significantly decreased NO3- -N export (p=0.0003) and average annual flow weighted concentration (p=0.0003) by 21.71 kg/ha (66%) and 1.85 mg/L (40%), respectively. The reduction of TSS export with SD was significantly lowered (p=0.001) by 1645 kg/ha (50%).Export of total phosphorus (TP) and orthophosphorus (OP) were both increased with the use of SD. The increase in TP export with SD was not found to be significant (p=0.19), but was 0.45 kg/ha (11%) greater than FD. Export of OP was 0.46 kg/ha (36%) greater which was found to be significant (p=0.07). The average flow weighted concentration of OP was significantly increased (p<0.0001) with SD by 0.28 mg/L (215%). The average flow weighted concentration of TP was significantly increased (p=0.01) with SD by 0.68 mg/L (124%). Although the increase in phosphorus concentration seems substantial, the overall increase in phosphorus loss was within the range of other reported studies for agricultural systems.Grain samples collected during the 2021 and 2022 harvest indicate that SD increased efficiency of fertilizer utilization with more applied fertilizer being utilized for grain production. The SD treatment significantly increased (p=0.0008) N transported in the harvested grain by 46.7 kg/ha (12%). The SD treatment significantly increased (p=0.001) P transported in harvested grain by 16.1 kg/ha (30%).

English

ISBN: 9798379879129Subjects--Topical Terms:

1070053
Copper.

Effects of Shallow Surface Ditches With Controlled Subsurface Tile Drainage on Drainage Flows, Nutrient Exports, and Crop Yields in Eastern North Carolina /
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520 $a Unrestricted conventional surface drainage ditches with subsurface tile (FD) are commonly used on the Eastern Seaboard to satisfy drainage needs. The large conventional FD ditches are efficient at drainage yet pose trafficability hazards, are direct pathways for nutrient export, and require the removal of valuable topsoil for installation. This thesis presents the findings of a field study that compared the FD ditches with small shallow ditches (SD) that utilize subsurface tile directed to a singular outlet equipped with a water management control structure capable of intense controlled drainage (CD).The conventional FD plots and SD had the same drain spacing for the surface ditches and subsurface tile, but the FD had uncontrolled outlets so no drainage management practice could be used. The SD system was installed with precision grade equipment so that ditches could be placed on an accurate grade and a precise surface crown could be placed between ditches. The shallow ditches were installed to a maximum depth of 30 cm.Crop yields were evaluated over nine crop seasons under a corn and soybean rotation. The SD system significantly increased yields in eight of nine seasons with an average increase of 0.4 Mg/ha (4%) over five years for corn and 0.5 Mg/ha (14.3%) increase over four years for soybeans.Outflows from the drainage systems were monitored for a 20 month period to determine the impact on drainage flow and nutrient export. The SD plots significantly decreased drainage (p=0.0001) over the study period by 48%. The SD treatment also decreased nitrate-N (NO3 - -N) concentrations found in the drainage water and the export of both NO3 - -N and total suspended solids (TSS). The SD ditches significantly decreased NO3- -N export (p=0.0003) and average annual flow weighted concentration (p=0.0003) by 21.71 kg/ha (66%) and 1.85 mg/L (40%), respectively. The reduction of TSS export with SD was significantly lowered (p=0.001) by 1645 kg/ha (50%).Export of total phosphorus (TP) and orthophosphorus (OP) were both increased with the use of SD. The increase in TP export with SD was not found to be significant (p=0.19), but was 0.45 kg/ha (11%) greater than FD. Export of OP was 0.46 kg/ha (36%) greater which was found to be significant (p=0.07). The average flow weighted concentration of OP was significantly increased (p<0.0001) with SD by 0.28 mg/L (215%). The average flow weighted concentration of TP was significantly increased (p=0.01) with SD by 0.68 mg/L (124%). Although the increase in phosphorus concentration seems substantial, the overall increase in phosphorus loss was within the range of other reported studies for agricultural systems.Grain samples collected during the 2021 and 2022 harvest indicate that SD increased efficiency of fertilizer utilization with more applied fertilizer being utilized for grain production. The SD treatment significantly increased (p=0.0008) N transported in the harvested grain by 46.7 kg/ha (12%). The SD treatment significantly increased (p=0.001) P transported in harvested grain by 16.1 kg/ha (30%).
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