Soil properties and productivity of medicinal crops in Dendrocalamus Stocksii (Munro.) based agricultural system

Abstract

The research work entitled “Soil properties and productivity of medicinal crops in Dendrocalamus stocksii (Munro.) based agrisilvicultural system” was caried with an aim to assess the growth and productivity of D. stocksii (4-year-old) and intercrops in an agrisilvicultural system. The study also monitored changes in soil physicochemical properties under D. stocksii and the understory PAR availability under varying densities of D. stocksii. Apart from these, leaf litter production pattern under this bamboo species was also studied. The experiment was laid out in Split- plot design involving three spacing treatments of D. stocksii (8x8m, 8x6m, 8x4m) intercropped with three medicinal crops (Kasturi turmeric, turmeric and ginger) along with a bambooless control treatment (sole crops) each replicated thrice which was laid out in the ongoing All India Coordinated Research Project on Agroforestry trial plots at the Instructional Farm, College of Agriculture, Kerala Agricultural University, Vellanikkara, Trissur during 2021-2022. The results of the study revealed that the growth attributes of D. stocksii were significantly affected by varied spacings. As the spacing increased from closer to wider, all growth parameters (except the culm height and internodal length) were found to increase and 8x8 m was the most favourable. Under different spacings, the understory PAR transmittance decreased with decrease in spacing. The mean PAR transmittance percentage across the seasons in 8x8m, 8x6 m and 8x4 m was 54.79, 43.52 and 34.15 respectively. Mean Mid-day PAR transmittance was 64.64, 53.88 and 42.15 % under bamboo spacings of 8x8, 8x6 and 8x4 m respectively. Mean LAI in 8x4 m was 4.35 and lowest was recorded in 8x8 m (2.31) which was 46.90 % higher than under the closest spacing 8x4 m. For the litterfall, a bimodal seasonal pattern was evidenced with the maximum litterfall observed under closest spacing (10.11 Mg ha–1) and lowest under widest spacing (7.86 Mg ha–1). The growth parameters like plant height, number of leaves per plant, leaf length and leaf breadth of all intercrops were found maximum at 8x8 m spacing and lowest under open plot. Tillers per plant of Kasturi turmeric and turmeric was maximum in open plot followed by 8x8 m spacing while ginger recorded the maximum tillers per plant under 8x8 m and lowest was under 8x4 m spacing. The rhizome yield of intercrops was significantly influenced by varying spacings of D. stocksii. The highest rhizome yield for Kasturi turmeric (25.22 Mg ha-1) and turmeric (22.42 Mg ha-1) was noted in open plot which was on par with the widest spacing of 8x8 m (23.89 and 21.02 Mg ha-1) and the lowest yield (13.36 and 12.20 Mg ha-1) was noticed in 8x4 m spacing. In case of ginger, highest rhizome yield (19.92 Mg ha-1) was observed at bamboo spacing of 8x8 m. The oleoresin content of Kasturi turmeric, turmeric and ginger was found higher (11.37, 9.07 and 4.84 %) under intermediate spacing (8x6 m) which was at par with 8x8 m (10.28, 8.28 and 4.54) and lowest in open plot. All the physico-chemical properties of soil under intercropping system were decreased with increase in spacings and soil depths except for bulk density and soil pH. Soil electrical conductivity (EC) and soil moisture content (SMC) was found higher in 8x4 m spacing and lowest was in open plot. The soil available NPK was also found maximum in closest spacing (8x4 m) (Kasturi turmeric: 308.78, 25.96, 151.42 kg/ha; turmeric: 315.34, 24.85,157 kg/ha; ginger: 330.99, 25.23, 146.45 kg/ha respectively) and lowest was in open plots of these crops. Soil organic carbon (SOC) under intercropping of bamboo+ Kasturi turmeric, turmeric and ginger was highest at 8x4 m (1.08, 1.06 and 1.09 % respectively). Soil available S, Ca and Mg at top soil was recorded highest in 8x4 m spacing (Kasturi turmeric 8.31, 227.50, 151.42 mg/kg; Turmeric 9.67, 222.32, 157 mg/kg; Ginger 10.53, 212.14, 146.45 mg/kg respectively) and lowest was in the open plot. All the physicochemical properties of soil under bamboo within 1 m distance from clumps showed decreasing trend with increase in spacings and soil depths except bulk density and soil pH which showed increasing trend. The EC, SMC, SOC, NPK, S, Ca and Mg was maximum under closest spacing (0.285 dS m–1, 17.59 %, 1.12 %, 324.12, 28.60, 161.1 kg/ha, 10.06, 278.40 and 124.52 mg/kg respectively) and lowest was under bamboo less open plot. Total gross and net return/ha (bamboo + intercrops) was highest under 8x8 m spacing compared to open plot (sole crops) and as spacings decreased these returns also decreased. When compared to spacing and intercrop combinations, Kasturi turmeric, turmeric and ginger intercropped under widest spacing (8x8 m) showed better B:C ratio (3.25, 2.48 and 2.47 respectively). It is concluded that widest spacing (8x8 m) is more favourable to bamboo growth as compared to closer spacings. At the same time, the wider (8x8 m) spacing proved to be better for utilizing the growing space for intercropping with higher productivity compared to the closer spacings. All the intercrops performed well with a mean daily PAR transmittance of 54.79 % and a mid-day PAR transmittance of 64.64 % available to the understorey. The mean PAR reduction (45.21 %) under 8x8 m spacing proved acclamatory for ginger with higher productivity compared to open conditions, while in case of Kasturi turmeric and turmeric, it caused marginal decrease in productivity compared to open conditions. Physico-chemical properties was found to be improved with maximum amount of nutrient reserves in closest spacing (8x4 m). This closest spacing could be viewed as a good option for the reclamation of poor and degraded lands while the widest spacing (8x8 m) could be recommend as a viable farming practice for higher economic returns in the humid tropic region of Kerala.