Response of canola to moisture stress and foliar application of stress tolerance inducing chemicals

Abstract

Moisture stress is a major factor which limits crop productivity in arid and semi arid regions of the world. The aim of this study was to evaluate the effect of moisture stress and moisture stress mitigating chemicals on canola. A two years field experiment was conducted at Agricultural Research Institute Tarnab Peshawar-Pakistan during 2015-16 and 2016-17. Canola hybrid 401 was grown under four moisture levels (full irrigation, 10%, 20% and 30% reduced irrigation water). Three chemicals (salicylic acid, potassium nitrate and methanol at the rate of 0.5mM, 1% solution and 20% solution respectively) were applied at three growth stages (bud formation, flowering, pod formation). Water spray and control were also included for comparison. RCB design with split plot arrangement having three replications was used. Moisture levels were assigned to main plot while combination of chemicals x crop growth stages were assigned to subplots. The experiment was conducted under high tunnel structures. Top of structures were covered with transparent plastic for protection from rainfall, while sides were kept open for free movement of air. Moisture stress was imposed at rosette stage (50 days after sowing) of the crop. Days to 50% flowering, days to 50% pod formation, days to maturity, plant height, leaf area (LA), leaf area index (LAI), net assimilation rate (NAR), crop growth rate (CGR), leaf relative water content (LRWC), pods plant-1, seeds pod-1, thousand seed weight, biological yield and seed yield decreased with each level of decline in soil moisture content. The effect of 20% and 30% reduced irrigation water was more severe on growth rate, yield and yield components. Days to 50% flowering, pod formation and maturity delayed with full irrigation. Seed yield decreased by 7.2%, 14.7%and 21% with reduction of irrigation water by 10%, 20% and 30% respectively compared to full irrigation (2062 kg ha-1). Biological yield also decreased by 5.2%, 9.7% and 15.4%with reduction of irrigation water by 10%, 20%, and 30% respectively compared to full irrigation (20052 kg ha-1). Seed oil and protein content decreased with 20% and 30% reduced irrigation water. Foliar application of chemicals significantly affected growth and yield of canola under full and limited moisture conditions. Salicylic acid (SA) delayed days to flowering, pod formation and maturity. Salicylic acid also improved CGR, NAR, LAI, LRWC, seed oil and protein content. Potassium nitrate (KNO3) was at par with salicylic acid for most of the parameters. Potassium nitrate showed significant effect on seed yield and thousand seed weight compared to salicylic acid. Potassium nitrate, salicylic acid and methanol increased seed yield by 7.9%, 7.1% and 4.2% respectively compared to control (1739 kg ha-1). Most of the parameters significantly increased with chemical application v compared to water spray and control. Water spray significantly affected plant height, LRWC and reduced aphids incidence compared to control. Application time of spray at different growth stages significantly affected CGR, NAR, relative water content, LAI and population of aphids. It is concluded that application of SA (0.5mM) and KNO3 (1%) at bud formation stage of canola were more effective in increasing CGR, NAR, biological yield and seed yield under full and limited irrigation water.