Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Burgos, Nilda R.

Committee Member

Srivastava, Vibha

Second Committee Member

Roberts, Trenton L.

Third Committee Member

Mauromoustakos, Andronikos T.

Keywords

Weed sciences

Abstract

Biostimulants can improve plant tolerance to abiotic stress by improving plant growth and development. Herbicides cause abiotic stress to crops shortly after application, which may affect yield. Preliminary tests showed that rice yield benefits from Atonik seed treatment or tank-mixture of Atonik with foliar herbicides. Experiments were conducted in the field and greenhouse to: (1) determine if seed treatment with Atonik improves rice tolerance to pre-plant herbicides; (2 and 3) evaluate the effect of Atonik seed treatment on rice response to pre-emergence and delayed pre-emergence herbicides; and (4) determine if Atonik improves crop safety of foliar-applied herbicides. Field studies were conducted in silt loam and clay loam soil in Rohwer, AR except the foliar tank-mix study (silt loam only). Greenhouse studies were conducted in Fayetteville, AR. The greenhouse experiments were conducted using silt loam soil from Fayetteville, AR, and the experimental design was a split-plot randomized complete block design with four replications. Greenhouse study 1 had seven levels of Atonik ranging from 0 to 3.5 ml kg-1 seed with increments of 0.5 ml kg-1 of seed. The herbicides tested were the same as in the field. The field study (1) was a seed treatment x preplant herbicide test with 24 treatments, with herbicide (12 levels) as whole plot and Atonik concentration (2 levels) as subplot factors. Atonik rates were 0 and 0.225% v/wt of seed. The experimental design was split-plot randomized complete block with four replications. In both soil types, injury was less than 10% except with Canopy and Trivence, which caused > 60% injury. Seed treatment with Atonik did not reduce injury, and generally did not benefit rice yield in clay loam soil; however, in the silt loam soil yield increased numerically from 1043 to 1882 kg ha-1 in 9 of 12 treatments (mean = 1294 kg ha-1). The field study (2) was a seed treatment x pre-emergence herbicide test with 20 treatments, with herbicide (4 levels) as whole plot and Atonik concentration (5 levels) as subplot factors. Atonik rates were: 0, 0.375, 0.75, 1.5, and 3.0 ml kg-1 seed 'RT7321FP'. In both soil types, injury was generally 60% injury. Seed treatment with Atonik did not reduce injury and generally did not benefit rice yield. The yield was numerically highest (12,500 kg ha-1) with the nontreated check. In the greenhouse (1) pre-emergence test, the highest biomass (9g 2plants-1) was produced with 2.5 ml kg-1 seed treatment without herbicides. However, in the delayed pre-emergence study, the highest biomass was obtained with quinclorac + thiobencarb applied to rice treated with 1.0 ml kg-1 seed. A field study (4) was conducted with foliar herbicides (11 levels) as wholeplot and Atonik concentration (0, 0.075 and 0.225 % v/v) as subplot factors. Atonik was tank-mixed with herbicides and applied to V3 rice 'RT7321FP'. Overall, the application of Atonik with foliar rice herbicides did not increase yield significantly regardless of Atonik rate. Plots treated with quinclorac + propanil without Atonik produced the highest yield (13491 kg ha-1). This yield was 18% higher than the nontreated check. In the greenhouse study (2), the highest biomass (30g 3plants-1) was produced when rice plants were treated with 0.075% v/v Atonik without herbicide. Overall, these experiments indicated that the benefit from Atonik is small or none and is herbicide dependent.

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