In arid and semiarid areas, wine grapes are frequently managed using regulated deficit irrigation (RDI) to control vegetative growth. To understand the distribution of soil moisture using RDI in a drip-irrigated vineyard, we collected soil samples after several irrigation events around six drip emitters in two ‘Cabernet Sauvignon’ and two ‘Merlot’ vineyards from late July through Mar. 2002 and 2005. The March sampling depicts soil moisture status before budbreak after winter precipitation. Soil samples were collected in four depth increments at 16 locations in a half-circle radius from immediately below the emitter to a depth of 60 cm. Both gravimetric and volumetric soil moisture content were determined. Soil moisture varied by depth, distance from the emitter, and sampling time. During late-season irrigation events, 50% to 75% of the sampled area contained plant-available water, which was less than expected. When calculated as plant-available soil moisture, regardless of time of sampling, soil sampled across a 0- to 45-cm depth provided the most representative indication of soil moisture status. Additionally, sampling directly under the emitter or directly under the drip line could result in skewed measurements compared with the sampled area. The data suggest that collecting soil samples within a 20- to 40-cm radius, either diagonal or perpendicular to the drip line emitter position, will best reflect the amount of plant-available soil water. Additionally, monitoring should be conducted on both sides of the row around each emitter selected and then averaged to avoid any patterns from hilling or disruption in water flow patterns.

Potato (Solanum tuberosum) production in Washington State's Central Columbia Plateau faces nitrogen (N) management challenges due to the combination of coarse textured soils (sandy loam to loam) and hilly topography in this region as well as the high N requirement of potato. Potato growth and development can vary with the N availability across the field. In this 2-year study, two adjacent potato fields were selected each year (1999 and 2000). Each field was soil sampled on a 200 × 200 ft (61.0 m) grid to establish existing soil N content. One field was preplant fertilized with variable N rate while the other was conventionally preplant fertilized, applying a uniform rate across the field based on the field average. During the growing season, each field was monitored for nitrate leaching potential using ion exchange membrane technology. Soil and plant nutrient status were also monitored by collecting in-season petiole and soil samples at two key phenological stages, tuber initiation and tuber bulking. Overall this research showed that variable rate preplant N fertilizer management reduced N leaching potential during the early part of the growing season, but did not persist the entire season. Since preplant N accounted for only 40% of the total seasonal N applied, it is possible that further gains could be made with variable rate in-season N application or with variable rate water application.

ImportanceType 2 diabetes (T2D) is the leading cause of kidney disease in the US. It is not known whether glucose-lowering medications differentially affect kidney function.ObjectiveTo evaluate kidney outcomes in the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness (GRADE) trial comparing 4 classes of glucose-lowering medications added to metformin for glycemic management in individuals with T2D.Design, Setting, and ParticipantsA randomized clinical trial was conducted at 36 sites across the US. Participants included adults with T2D for less than 10 years, a hemoglobin A1c level between 6.8% and 8.5%, and estimated glomerular filtration rate (eGFR) greater than or equal to 60 mL/min/1.73 m2 who were receiving metformin treatment. A total of 5047 participants were enrolled between July 8, 2013, and August 11, 2017, and followed up for a mean of 5.0 years (range, 0-7.6 years). Data were analyzed from February 21, 2022, to March 27, 2023.InterventionsAddition of insulin glargine, glimepiride, liraglutide, or sitagliptin to metformin, with the medication combination continued until the HbA1c was greater than 7.5%; thereafter, insulin was added to maintain glycemic control.Main Outcomes and MeasuresChronic eGFR slope (change in eGFR between year 1 and trial end) and a composite kidney disease progression outcome (albuminuria, dialysis, transplant, or death due to kidney disease). Secondary outcomes included incident eGFR less than 60 mL/min/1.73 m2, 40% decrease in eGFR to less than 60 mL/min/1.73 m2, doubling of urine albumin-to-creatinine ratio (UACR) to 30 mg/g or greater, and progression of Kidney Disease Improving Global Outcomes stage. Analyses were intention-to-treat.ResultsOf the 5047 participants, 3210 (63.6%) were men. Baseline characteristics were mean (SD) age 57.2 (10.0) years; HbA1c 7.5% (0.5%); diabetes duration, 4.2 (2.7) years; body mass index, 34.3 (6.8); blood pressure 128.3/77.3 (14.7/9.9) mm Hg; eGFR 94.9 (16.8) mL/min/1.73 m2; and median UACR, 6.4 (IQR 3.1-16.9) mg/g; 2933 (58.1%) were treated with renin-angiotensin-aldosterone inhibitors. Mean chronic eGFR slope was −2.03 (95% CI, −2.20 to −1.86) mL/min/1.73 m2 per year for patients receiving sitagliptin; glimepiride, −1.92 (95% CI, −2.08 to −1.75) mL/min/1.73 m2 per year; liraglutide, −2.08 (95% CI, −2.26 to −1.90) mL/min/1.73 m2 per year; and insulin glargine, −2.02 (95% CI, −2.19 to −1.84) mL/min/1.73 m2 per year (P = .61). Mean composite kidney disease progression occurred in 135 (10.6%) patients receiving sitagliptin; glimepiride, 155 (12.4%); liraglutide, 152 (12.0%); and insulin glargine, 150 (11.9%) (P = .56). Most of the composite outcome was attributable to albuminuria progression (98.4%). There were no significant differences by treatment assignment in secondary outcomes. There were no adverse kidney events attributable to medication assignment.Conclusions and RelevanceIn this randomized clinical trial, among people with T2D and predominantly free of kidney disease at baseline, no significant differences in kidney outcomes were observed during 5 years of follow-up when a dipeptidyl peptidase 4 inhibitor, sulfonylurea, glucagonlike peptide 1 receptor agonist, or basal insulin was added to metformin for glycemic control.Trial RegistrationClinicalTrials.gov Identifier: NCT01794143

Understanding water and nutrient movement in arid climate-regulated deficit, drip-irrigated vineyards is imperative for understanding grape vine canopy management. However, little research has been conducted in these environments to aid in the understanding of where the vine accesses nutrients and/or soil water and how that translates into soil and/or plant tissue sampling approaches. We used bromide (Br) as a tracer to study nitrate movement in soils as well as into grape leaves in two ‘Merlot’ vineyards in central Washington State. Bromide movement closely followed water movement. Although Br was detectable in grape petioles, it was not detectable in leaf blades, likely as a result of a dilution factor related to the amount of tissue. Relationships between soil Br and soil moisture as well as petiole and soil Br concentrations suggests that soil sampling for nitrate should be taken from a diagonal position between the vine and the emitter, between 20 and 60 cm from the drip line. This is consistent with the recommendation for soil moisture sampling in a published companion study.