Effect of Different Fertilizers and Planting Density on Morphological Traits and Photosynthetic Pigments Content in Isabgol (Plantago ovata Forsk)

Medicinal plants in the world are very important and currently the demand for medicinal herbs is on the rise due to higher requirement of products need in the pharmaceutical, health and food industry. Therefore, the assessment of various systems of plant nutrition is one of the important needs of agricultural planning in order to achieve high yield with high quality, especially in medicinal plants. Manure increase soil fertility and improves the growth and yield. This experiment was conducted to investigate the effect of planting density and single or combined application of cow manure (CM) and chemical fertilizers (CF) on growth, yield and pigment content of Isabgol (Plantago ovata Forsk).

In order to evaluate the effects of different levels of fertilizer on isabgol (Plantago ovata Forsk) an experiment was arranged as factorial based on a randomized complete block design with three replications at Sarayan Faculty of Agriculture, University of Birjand, during 2017. Experimental factors were included: Fertilization treatments consisted of single (40 ton.ha-1 CM and 40 kg.ha-1 CF from the source of NPK) and combined (40 ton.ha-1 CM + 20 kg.ha-1 CF and 20 ton. CM + 40 kg.ha-1 CF) application of organic and chemical fertilizers along with a control treatment (no-fertilizer) which were evaluated at three levels of density (20, 40 and 60 plants.m2). Measurements of chlorophyll a, b, carotenoid and SPAD: Firstly, 0.1g samples were taken from the collected leaves. Subsequently each sample was extracted by 80% acetone and put in the centrifuges with rotation speed of 6000 per minute for 10 minute. Absorbance using a spectrophotometer at wavelengths of 470, 647, 663 nm was measured. Also, chlorophyll index was measured by manual chlorophyll meter. Measurements of Yield and yield components: In the sampling stage (full flowering stage), 3 plants of cultivation lines were harvested with respect to the elimination of marginal effects. After measuring plant height, the plants were cut from above the soil, immediately weighed (fresh weight) and then the samples were placed in separate bags and after drying in an oven at 72°C for 48 hours, the leaf weight, total dry weight and grain yield of each sample were measured. Finally, Statistical analyses were carried out by ANOVA, with  least significant difference test (LSD) at 5% probability level for subsequent pairwise comparisons.

 The results indicated the significant effect of treatments on plant dry weight, biological yield, seed yield and chlorophyll b content. The highest biological and seed yields (2080 and 806.6 kg.ha-1, respectively), were obtained from planting density of 60 plants m2, while the highest leaf chlorophyll content was gained from 20 plants m2 treatment. The effect of fertilizer resources on all traits (except plant dry weight) and interaction effect of experimental factors on all studied indices were no-significant. The plant showed an appropriate adaptation to low nutritional and its maximum yield was obtained when at least 60 plants.m2 was used.

Based on the obtained results, it could be concluded that isabgol is a low-input medicinal plants in terms of nutrient requirements. Therefore, it seems that the application of fertilizer resources in crops which are located prior to isabgol in a rotation and availability of remaining nutrients can provide the nutritional requirements of this plant. Moreover, consider to open canopy of the plant even when the plant density was 60 plant.m-2, it seems that more densities must be considered in future studies.