Evaluation of Organic Fertilizers on Yield and Yield Components in Intercropping of Roselle (Hibiscus sabdariffa L.) and Cow Pea (Vigna unguiculata L.)

Intercropping due to better use of environmental resources, has led to this type of agronomic system in livelihoods farming having an important role in providing food and has a special place in the design of sustainable agro-ecosystems. The superiority of yield in intercropping cultivation is due to the combination of various factors such as better use of soil moisture, light and nutrients. Organic fertilizers such as vermi compost and animal manure lead to improve the performance of plant by increasing the availability of moisture and nutrients available to plants, and consequently increase soil organic matter. Considering the importance of suitable cropping pattern and determining the optimal feeding systems agricultural systems, the current study aimed to evaluate intercropping systems of Roselle and cowpea with organic fertilizers and the introduction of best cultivation model as well as the optimal amount of fertilizer. The experiments were carried out in the Sistan region.

In order to investigate the effects of vermicompost and cow manure on morphological characteristics in Roselle and cowpea, the experiments conducted at the Research Institute of Zabol University during growing season of 2016. Treatments experiment included three levels of organic fertilizers as the main plot including cow fertilizer (30 t.ha-1), vermicompost fertilizer (15 t.ha-1) and control as well as 5 levels of intercropping patterns including (100% Roselle, 100% cowpea, 50% Roselle+ 50% cowpea, 25% Roselle+ 75% cowpea and 75% Roselle+ 25% cowpea). As subplot agent, from the middle of each plot five plants were harvested randomly at the end of the growing season to determine yield. Finally, data analysis was performed using SAS version 9.1. Comparison of mean treatments was performed using Duncan's multiple range test at 5% probability level. Irrigation was performed every day (7 days) on average according to the requirement of both plants. Relative performance of each component was calculated to calculate the Land Equivalent Ratio (LER).

The results of variance analysis showed that the interaction of organic fertilizers and intercropping except for the traits of stem height and chlorophyll content (a,b) of cowpea, is significant for all traits measured Roselle and cowpea. The highest dry sepal yield Roselle (1170.58 kg.ha-1) was obtained in vermicompost and 50% Roselle and 50% cowpea and highest Seed yield of cowpea (2418.3 kg.ha-1) was for vermicompost+ cowpea 25%+ Roselle 75%. The use of organic fertilizers improves vegetative growth and yield components by releasing nutrients gradually. Intercropping is useful when the yield of the intercropping product is greater than the maximum single craft product. Yield increment can be attributed to the better use of the available resources by the two plants, the morphological differences between them and the lower weed in the intercropping system. The results showed that plant systems have a significant effect on the Land Equivalent Ratio (LER). The highest LER (5.37) of Treatment Vermicompost+ cowpea 25% + Roselle 75%, showed the advantage of intercropping over sole crop. Concerning the superiority of intercropping to sole crop, it can be argued that increasing yield is due to increased resource efficiency in intercropping system.

In the present study the highest sepal yield of Roselle was obtained in intercropping system with vermicompost with 50% Roselle and 50% cowpea and highest seed yield of cowpea was observed in intercropping system with vermicompost with cowpea 25%+ Roselle 75%. The results of the experiment indicate that the performance of both species was influenced by different ratios of cultivation and fertilization. Intercropping cultivation in Roselle and cowpea is much more profitable than single cultivation, because of the significant and beneficial interactions that make use of environmental resources (such as water, nutrients, and sun light).