Intercropping mulberry (Morus spp.) with aromatic medicinal plants (Rosemary, Lavender, and Centella): A field study on growth, yield, soil health, and economic returns under temperate conditions of Kashmir

Introduction

Sericulture is a labour-intensive agro-based industry providing rural employment and foreign exchange through silk exports. In temperate regions like Kashmir, only two commercial rearing cycles (spring and autumn) are feasible leaving land underutilized for ∼9 months annually. Farmers hesitate to allocate land exclusively to mulberry due to low returns per unit area and competition with horticultural/food crops (Mir et al. 2022) [9] . Sericulture is facing tough competition due to limited land resources and competition with other agricultural crops. Therefore, there is an urgent need to develop mutual harmony between sericulture and agriculture for sustainable co-existence. In general most of the of the sericulture farmers have very small land holdings and depend mainly upon family labor and simple tools, they neither have the capacity to take risk nor have enough land to diversify the cropping system. Thus, by growing of short duration crops farmers get additional benefit from intercrops (Ahasn et al. 1989) [1] . Intercropping, growing two or more crops simultaneously in proximity maximizes resource use, suppresses weeds, enhances soil fertility and generates supplementary income (Mousavi et al. 2011) [10] . This practice has been used for centuries by farmers all over the world as a way to increase yields, improve soil health and reduce risks associated with monoculture farming. It is important practice of agriculture allowing farmers to make the most efficient use of their land and other resources besides taking advantage of complementary growth patterns, nutrient uptake and pest control, ultimately leading to increased productivity and yield. Intercropping has also been recognized to be an environmentally sustainable way to produce food (Rafiqui et al. 2023) [14] .

The most common objective of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop and thereby to augment the income. Careful planning is required, taking into account the soil, climate, crops and varieties. It is particularly important not to have crops competing with each other for physical space, nutrients, water, or sunlight. Intercropping of compatible plants also encourages biodiversity, by providing a habitat for a variety of insects and soil organisms that would not be present in a single crop environment. This biodiversity can in turn help to limit outbreaks of crop pests by increasing the diversity or abundance of natural enemies, such as spiders or parasitic wasps. Increasing the complexity of the crop environment through intercropping also limits the places where pests can find optimal foraging or reproductive conditions (Rajegowda et al. 2020) [15] . Mulberry's wide spacing (9 ft × 8 ft in tree system), annual pruning, and minimal chemical inputs make it ideal for intercropping with shallow-rooted, low-canopy, shade-tolerant species (Fotadar et al. 2012) [3] . Aromatic medicinal plants are high-value, low-volume crops suitable for intercropping in mulberry due to differential nutrient uptake, pest-repellent properties, and market demand for essential oils/phytochemicals (Madhusudan et al. 2015; Li et al. 2022) [8,6] . Previous studies reported successfully integration of lavender, lemon grass, and mint with mulberry under Kashmir conditions (Fotadar et al. 2012) [3] . However, sys-tematic evaluation of rosemary (Rosmarinus officinalis), lavender (Lavandula angustifolia), and centella (Centella asiatica) all commercially important aromatics is lacking. This study aimed to assess compatibility of the three aromatics with mulberry, quantify growth and yield (especially detailed rosemary metrics), evaluate impacts on mulberry leaf quality, silkworm performance, monitor soil health, and compute economics under temperate Kashmir conditions.

Materials and Methods Experimental Site and Design

The trial was conducted (2023-2024) at the College of Temperate Sericulture, Mirgund (34°02'N, 74°45'E; 1580 m asl), SKUAST-Kashmir. Soil was silty-clay loam (pH 6.8, OC 0.92%, available N 285 kg ha -1 , P 18 kg ha -1 , K 220 kg ha -1 ). Treatments comprised sole mulberry (control) and mulberry intercropped with rosemary, lavender, or centella in randomized complete block design (RCBD) with three replications. Plot size: 0.05 ha (50 mulberry trees/plot). Mulberry cv. Goshoerami (tree system, 9 ft × 8 ft) was planted in 2021. Intercrops were transplanted in June 2023 (Year 1) at 60 cm × 45 cm (rosemary/lavender) and 30 cm × 30 cm (centella) between mulberry rows, avoiding 1 m radius around tree trunks.

Cultural Practices

Mulberry received FYM @ 20 t ha -1 yr-1 + NPK (300:120:120 kg ha -1 ). Intercrops received 50% recommended NPK (rosemary/lavender: 100:50:50; centella: 80:40:40 kg ha -1 ). Irriga-tion (drip, 15-day interval) and manual weeding were uniform. No pesticides were applied to maintain chemical-free produce.

Observations Mulberry Parameters

Leaf yield (kg tree-1), moisture content (%), protein (%), and chlorophyll (SPAD) were recorded post-spring/autumn pruning. Silkworm rearing (cv. NB4D2) used standard proto-cols; cocoon yield, shell ratio, and filament length were measured.

Aromatic Plant Parameters

Plant height, branches plant -1 , fresh/dry herbage yield (t ha - 1 ) were recorded at peak flowering (rosemary: Aug; lavender: July; centella: Sep). Essential oil was extracted by hydro-distillation (Clevenger); yield (%) and oil (kg ha -1 ) computed. Detailed Rosemary Yield Data (per harvest, averaged across replications):

Soil Analysis

Pre-and post-experiment (0-30 cm) samples were analyzed for pH, OC (Walkley-Black), N (Kjeldahl), P (Olsen), K (flame photometry).

Economics

Costs (inputs, labour) and returns (mulberry leaf @ 25 kg-1; cocoons @ 550 kg-1; rosemary herb @ 120 kg-1 dry, oil @ 4500 kg-1; lavender @ 180 kg-1 dry, oil @ 6000 kg-1; centella @ 80 kg-1 fresh) were calculated. B:C ratio computed.

Statistical Analysis

ANOVA (RCBD) using SPSS 26.0; means separated by LSD (p = 0.05).

Results and Discussion Mulberry Growth and Leaf Yield

Intercropping did not affect mulberry height, branches, or leaf yield (Table 3). Spring leaf yield: 18.2-18.6 kg tree-1; autumn: 12.4-12.7 kg tree-1. No competition due to differential canopy (mulberry >2 m; aromatics <1 m) and root depth (Liu et al. 2022) [7] . Silkworm rearing: ERR 98%, cocoon weight 1.92-1.95 g, shell ratio 23.1-23.4%, filament 920-935 m (nonsignificant). Murugesh 2009 investigated the potential for intercropping of mulberry with cluster bean, cowpea, green gram, soybean, gingelly and coriander. The study found that intercropping of cluster-bean and cowpea in mulberry maximizes yield of mulberry both quantitatively and qualitatively as compared to monoculture farming.

Aromatic Plant Performance

Rosemary outperformed others (Table 4). Rosemary: robust growth, drought tolerance, and allelopathic weed suppression (?). Lavender suffered minor frost damage; centella high biomass but low value.

Soil Health

Soil has a direct bearing upon the growth and development of any crop as it is the soil which provides the plant with all the necessary conditions required for growth. Therefore, soil health is fundamental to healthy crop production. Rosemary increased OC (+ 18%), N (+ 14%), P (+ 22%) vs. control due to litter decomposi-tion and reduced erosion (8). A study conducted in China found that intercropping mulberry (Morus alba L.) with peanut (Arachis hypogaea L.) improves the diversity and richness of soil microorganisms in farmland and promotes soil humus (Khan et al. 2015).

Economics

Intercropping has proven to be a better option than sole cropping. Intercropping often leads to increased economics and higher monetary returns. Mulberry-rosemary: gross return 4.85 lakh ha -1 , net 3.68 lakh, B:C 4.12 (highest). Additional income from rosemary is 1.62 lakh ha -1 . Intercropping of mulberry with cash crop can act as a booster for enhancing farm income. Medicinal plants such as Rauvolfia, Plumbago, Asparagus and Sarpagandha have been grown as an intercrop with mulberry without affecting sericulture in Uttarakhand (Prasad et al. 1999) [13] . Other medicinal plants like Lavendula officinalis (Lavender), Atropa belladonna (Belladonna) and Echinecea purpurea (Purple coneflower) have been grown successfully under temperate climatic conditions of Kashmir as intercrop with mulberry (Pandey and Dhar 2013) [12] . Intercropping of Cymbopogon citratus (Lemon grass) and Mentha piperita (Mentha) has also been documented (Datta. 2007) [2] . Mulberry can successfully be intercropped with Aloe barbadensis (Aloe vera), Asparagus racemosus (Asparagus) and Acorus calamus (Sweet flag) (Kour et al. 2002) [4] . The prospects of intercropping of seven medicinal plants viz., Aloe barbandense (Aloe vera), Asparagus racemosus (Asparagus), Andrographis paniculata, Acorus calamus (Sweet flag), Plumbago zeylanica, Rauvolfia serpentine and Cyperus scarious under tree system of plantation has been evaluated (Li et al. 2022) [6] . Intercropping of mulberry with Crocus sativus (Saffron) which is a major cash crop of the region in Kashmir is reported to yield a significant income through sericulture during the lean period when there are no operations related to saffron cultivation (Liu et al. 2022) [7] .

Conclusion

Mulberry is one of the economically important crops which possess all the possible characteristics required to be integrated in an intercropped system with other agricultural crops. Rosemary is the most compatible aromatic intercrop for mulberry under Kashmir conditions, delivering superior yield, soil benefits, and profitability without affecting sericulture. Large-scale adoption recommended.

References

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