Investigate effect of humic acid and vermicompost application on yield and yield components of cumin (Cuminum cyminum L.)

The main objective of sustainable agriculture is to decrease the off-farm inputs such as chemical fertilizers, increased farm nutrient cycle through reduced tillage and the use of biological and organic fertilizers (Akbari and Gholami, 2016). Vermicompost and humic acid are samples of organic fertilizer that can be used to decrease the application of chemical fertilizers in order to achieve goals of sustainable agriculture. Vermicompost is considered as a rich source of macro/micro elements, vitamins, enzymes and growth stimulating hormones which accelerate the growth of medicinal plants. It also increases the access to nitrogen and phosphours by increasing the Nitrogen fixation and dissolving phosphorus (Prabha et al., 2007). The humic acid mentioned as an environmentally friendly, organic matter with low levels of hormonal-like compounds is useful in improving agriculture production (Samavat and Malakuti 2006). There has been little discussion about combined use of organic fertilizers on cumin. Thus, this study was conducted to investigate the effect of humic acid and vermicompost application on yield and yield components of cumin.
In order to evaluate the effect of different levels of vermicompost and humic acid on yield and yield components of cumin, an experiment was conducted as factorial based on randomized complete block design with three replications, in a field located in Mobarakeh city, during the growing season of 2016-2017. The treatments included of three levels of vermicompost (0, 5 and 10 t.ha-1) and four levels of humic acid (0, 2, 4 and 6 l.ha-1). At the end of the season, sampling were done and plant height, number of umbels, number of grain per umbel, 1000-Grain weight, grain and biological yield and harvest index were evaluated. Finally, for analysis of data, MSTAT-C software was applied and means were compared using the least significant difference (LSD) test at the probability level of 5%. Simple correlation of traits was obtained using SPSS version 16 software.
The results showed that vermicompost leads to a significant increase in investigated traits. So, use of 10 t.ha-1 vermicompost produced the maximum height and 1000-grain weight. Use of 5 and 10 t.ha-1 vermicompost increased the number of grain per umbel by 19 and 26 percent in comparison to control treatment respectively. Likewise, the results indicated that the simple effect of humic acid was significant on all the studied traits except harvest index. So that, the highest and lowest plant height, number of grain per umbel and 1000-Grain weight was obtained from 4 l.ha-1 and control treatments respectively. Interaction effect of vermicompost and humic acid influenced number of umbels, harvest index, grain and biological yield significantly. The maximum grain yield and number of umbel was observed with application of 4 and 6 l.ha-1 humic acid and 10 t.ha-1 vermicompost. In this regard, Akbari and Gholami (2016) reported that the greatest and lowest seed yield of Fennel obtained from 8 ton ha-1 vermicompost and control plots respectively. Also their results suggested that with humic acid foliar application, seed yield of Fennel increased about 18 percent (Akbari and Gholami, 2016). Highest efficiency of humic acid at all levels of vermicompost, obtained by application 4 liter of humic acid per hectare. Foliar spraying 4 l.ha-1 humic acid in combined with using of 0, 5 and 10 t.ha-1 vermicompost, caused a significant increasing in biological yield by 28.5, 14.2 and 9.8 percent compared with control (no foliar spraying) respectively. The results suggested that the between investigated traits, the maximum correlation of grain yield was observed with plant height (0.87**), number of umbels per plant (0.85**) and biological yield (0.84**) respectively.
Positive and significant correlation was found between yield and yield components, showing that an increase in one of yield components caused by use of organic fertilizers, could have a significant increasing effect on cumin yield. Overall, based on the results of present study, can be said application of organic fertilizers especially combined use of them, can be increased yield and yield components of plant and also alleviated environmental pollutions that created by use of chemical fertilizers and finally can be achieved to goals of sustainable agriculture.