Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Phosphorus enriched organic fertilizer, an effective P source for improving yield and bioactive principle of Senna (Cassia angustifolia Vhal.) B.B. Basak ⁎ , N.A. Gajbhiye ICAR-Directorate of Medicinal and Aromatic Plants Research, Boriavi, Anand 387310, Gujarat, India ARTICLE INFO Keywords: Rock phosphate charged compost Commercial P fertilizers Herbage yield Sennoside content Soil P pools ABSTRACT A pot culture experiment was conducted for two consecutive years in the late rainy season to evaluate the efficiency of rock phosphate charged compost as an organic P fertilizer source in senna. A fixed dose of P (40 kg ha -1 ), considered optimum for quality produce was supplied from different sources like Di-ammonium phosphate (DAP), Single Super Phosphate (SSP), Rock phosphate (RP) and RP charged compost (RPCC). Fresh and dry weight of leaves and pods per plant were recorded while sennoside content in leaves and pods samples were analyzed. Total fresh and dry herbage yield (leaf + pod) was significantly higher under different P treatments than the control. Application of RP, SSP, DAP and RPCC increased fresh herbage yield up to 6.7, 22.6, 35.1 and 48.1%, respectively over the control. Sennoside content did not respond to all P sources, but appli- cation of RPCC improved sennoside content in herbage. The highest herbage yield and sennoside content was recorded under RPCC application. Available P and microbial biomass P in soil after harvesting of crop was significantly higher under RPCC application but on par with DAP application. Both acid and alkaline phos- phatase activities in soil were influenced by P sources, while alkaline phosphatase found significantly higher with RPCC application. So, it can be concluded from the study that enriched compost effectively supplement costly chemical fertilizer like DAP as a P source. The result from the study may be recommended for efficient P management in both commercial as well as organic cultivation of senna. 1. Introduction Senna (Cassia angustifolia Vhal), popularly known as ‘Sonamukhi’ is one of the most important medicinal plants and widely used medicinal herb in ayurved, unani and also allopathic system of medicine. The major part of the production is exported in the form of leaves and pods which contain sennosides used for their laxative properties. India is the main producer and exporter of senna leaves and pods, producing an annual income to the tune of 300 million Indian rupees (Kayina et al., 2012). In India, senna leaves and pods generally contain 2.0–2.5% and 2.5–3.0% sennoside respectively. However, the large leaves and bold pods contain more than 2.5 and 3.0% sennoside respectively and fetch premium prices in the market. Recently, there is a growing demand for senna products in the national and international market. India has the monopoly in the international market and exported to around 55 countries, especially Venezuela, Japan and Europe (Kayina et al., 2012). In India, senna is widely grown in the state of Tamil Nadu, Andhra Pradesh, Rajasthan and Gujarat in an area about 25,000 ha (Gupta and Pareek, 1995; Pareek et al., 1983). Senna is non-nitrogen fixing member of Caesalpiniaceae family. It is a perennial undershrub legume that attains a height of 60–100 cm. Senna root does not form nodules hence it is responsive to application of nitrogen and phos- phorus (Ramamoorthy et al., 2003; Ilangovan et al., 1990). Plant nutrition through soil fertility management is quite important in any sustainable crop production. The nutrient use efficiency varies in relation to crop species as well as source of nutrients and ranges from 20 to 60% depending on the management practice and the chemical properties of the fertilizer source. The P use efficiency is usually low as plants can uptake only 20% of the total added P in soil through che- mical fertilizer (Bolland and Gilkes, 1998). Due to rising cost of com- mercial P fertilizer, there is a need of alternative P sources like locally available rock phosphate (Akande et al., 2005; Hinsinger and Gilkes, 1995). India has large deposits of low-grade rock phosphates which are not suitable for production of commercial phosphate fertilizer because of their low P content (Basak and Biswas, 2016). However, direct ap- plication of RP in agriculture is restricted due to its very low solubility, specifically in neutral and alkaline soils (Bangar et al., 1989). Blending the RP, either with organics or composting with plant residue has been found to be quite effective in increasing P availability from RP in soils (Basak, 2017; Verma et al., 2013; Akande et al., 2005). This might be https://doi.org/10.1016/j.indcrop.2018.02.026 Received 10 August 2017; Received in revised form 6 February 2018; Accepted 7 February 2018 ⁎ Corresponding author. E-mail addresses: biraj.basak@icar.org.in, biraj.ssac@gmail.com (B.B. Basak). Industrial Crops & Products 115 (2018) 208–213 0926-6690/ © 2018 Elsevier B.V. All rights reserved. T