No abstract

No abstract

Drainage water recycling (DWR) involves capture, storage, and reuse of surface and subsurface drainage water as irrigation to enhance crop production during critical times of the growing season. Our objectives were to synthesize 53 site-years of data from 1996 to 2017 in the midwestern United States to determine the effect of DWR using primarily subirrigation on corn (Zea mays L.) grain yield and yield variability and to identify precipitation factors at key stages of corn development (V1-V8, V9-VT, R1-R2, R3-R4, and R5-R6) that correlated to an increase in yield with DWR. A generalized additive model was used to quantify and characterize the relationship between precipitation and corn grain yield during corn development stages and to determine if that relationship differed between DWR and free drainage (FD). Corn yield response to precipitation was generally similar between DWR and FD, except during the critical period of V9-R2, in which DWR was more resilient to precipitation extremes than FD. Drainage water recycling was generally more responsive than FD in years with low and normal precipitation (<181 mm). When precipitation was low (27-85 mm) from V9 to R2, DWR had higher yields (77% of the site-years evaluated), with an average yield increase of 3.6 Mg ha −1 (1.2-7.5 Mg ha −1 ). Overall, FD had 28% greater yield variability than DWR. Additional research is needed on DWR impacts on different soils and locations throughout this region to improve the stability of corn yields and to develop automated DWR systems for enhancing efficiency of water management with increasing climate variability.

Capacitance type sensors have been widely used to monitor soil water content and salinity, but little is known about their response to specific ions in soil solution. The goal of this laboratory study was to investigate the sensitivity of two capacitance probes, ECH2O EC‐5 and EC‐10, to NO3 concentration in soil solutions, as well as to understand the differences in sensor response to the presence of other ions in the solutions. Forty‐five uniformly packed soil samples were prepared using a homogenized loam soil wetted to five volumetric water contents (VWC) with nine solutions containing different concentrations of NO3−, Cl−, or both. A two‐stage analysis of the normalized data revealed that ion type and concentration had a significant effect (P ∼ 0.01) only for the response of the EC‐10 probes operating at a frequency of 5 MHz. The response of the EC‐5 probes, operating at 70 MHz, was mainly explained by changes in VWC. Multiple linear regression models fitted to the EC‐10 response to individual solutions showed that concentration had a statistically significant predictive value only for samples wetted with NO3 solutions when temperature was incorporated in the model. The study confirmed that capacitance probes operating at a relatively low frequency of 5 MHz are more sensitive to changes in NO3 concentration than in Cl. We attributed this effect to the difference in ion mass that manifests through an increase in conductivity at ion‐specific frequency. Additional experimental work is needed, however, to accurately define optimal frequencies for measuring ion‐induced effects on dielectric measurement and to quantify interrelations between them.

This paper describes a multi-site and multi-decadal dataset of artificially drained agricultural fields in seven Midwest states and North Carolina, USA. Thirty-nine research sites provided data on three conservation practices for cropland with subsurface tile drainage: saturated buffers, controlled drainage, and drainage water recycling. These practices utilize vegetation and/or infrastructure to minimize off-site nutrient losses and retain water in the landscape. A total of 219 variables are reported, including 90 field measurement variables and 129 management operations and metadata. Key measurements include subsurface drain flow (206 site-years), nitrate-N load (154 site-years) and other water quality metrics, as well as agronomic, soil, climate, farm management and metadata records. Data are published at the USDA National Agricultural Library Ag Data Commons repository and are also available through an interactive website at Iowa State University. These multi-disciplinary data have large reuse potential by the scientific community as well as for design of drainage systems and implementation in the US and globally.