Investigating the Effect of Plant Density and Nutrient Application on Yield and Physiological Characteristics of Guar (Cyamopsis tetragonoloba)

Guar is a drought- and salt-tolerant annual summer legume which could be a potential alternative crop in semiarid regions. The increased use of guar gum in oil industries has increased the global demand for guar. An experiment was carried out during 2 consecutive years to investigate the effect of plant density and nutrient application on yield and physiological characteristics of guar. A factorial experiment based on randomized complete block design with three replications was conducted during the 2017 and 2018 growing seasons. Studied factors included phosphorous (P1: 0, P2: 75 kg/ha, P3: 150 kg/ha, P4: 225 kg/ha) and folic acid application (F1: 0, F2: 4 kg/ha, F3: 8 kg/ha, F4: 12 kg/ha) and plant density (D1: 10 plants/m² and D2: 20 plants/m²). Seed yield components, biological yield, protein value of seeds, leaf relative water content (RWC), guar percentage, and phosphorous-use efficiency (PUE) were measured. The highest biological yield (19058 kg/ha) and the highest seed yield (6129 kg/ha) were produced by the D1P4F4 and D2P4F4 treatments, respectively. Low plant density resulted in high biological yield, while high plant density resulted in high seed yield. The highest protein content (32.5%) was observed in D2P4F4. The highest RWC and gum percentage were produced in D2P4 and D2F4 treatments, respectively. An increase in P₂O₅ application rates up to 225 kg/ha significantly increased seed yield. The highest PUE (1.41 g/kg) was observed at a high plant density. Applying 225 kg/ha phosphorous fertilizer resulted in the highest PUE (1.5 g/kg). Therefore, increasing the application of phosphorous and folic acid could increase the yield and yield components of guar; a plant density of 20 plants/m² could also increase the biological yield. The results of this study may also help to extend guar cultivation in other regions.