MSc

Rice, the staple food in Kerala, is experiencing a significant production
deficit, with only one-fifth of the annual requirement being met. The key to
enhancing rice production is improving the productivity of existing agricultural
lands. Green leaf manuring offers a promising, cost-effective, and eco-friendly
solution to enhance productivity. Traditional green leaf manuring practices have
been abandoned in Kerala, primarily due to the scarcity of conventional green
leaves and various constraints, including labour and transportation. However, a
potential approach to rejuvenate this eco-friendly practice involves cultivating
green manuring trees and shrubs in rice bunds and maintaining them as hedges
through regular lopping.
This study entitled “Growth, green biomass production and crop interaction
of selected trees and shrubs on wetland paddy bunds” was carried out as two
separate experiments: a field experiment in State Seed Farm, Mannuthi, Thrissur;
and Survey and documentation in Ollukkara and Wadakkanchery blocks, Thrissur,
Kerala, during 2022-23. The study aimed to evaluate the survival, growth and
biomass production of green manuring trees and shrubs under ill-drained conditions
of wetland paddy bunds and their effects on paddy. The study also envisaged
surveying and documenting the indigenous knowledge, the current practices and
the farmer’s perspective on green leaf manuring in paddy fields of Ollukkara and
Wadakkanchery blocks in Thrissur district.
In the first experiment, different tree species like Gliricidia, Garuga,
Sesbania, Calliandra, Terminalia, mulberry, Gmelina, red gram and Cassia were
planted in paddy bunds at spacing of 1m in Randomized Block Design with three
replications. The results indicated that most species established well initially, with
some species showing exceptional growth and biomass production. Notably,
Sesbania (5.45 kg plant-1
), red gram (perennial) (4.10 kg plant-1
), Gliricidia (3.26
kg plant-1
), and Terminalia (2.54 kg plant-1
) emerged as top performers in terms of
annual biomass yield in the initial year of planting. At the same time, some species
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had slower growth rates (Cassia and Gmelina) and lower survival rates (Garuga
and Gmelina). Garuga had only 10% survival rate, hence found unsuitable for bund
planting in paddy. Interaction studies of trees on paddy indicate that paddy growth
and yield were not significantly influenced by bund planting in the initial year of
tree growth. Soil properties of paddy, like pH and nutrient content, except the
available nitrogen content, didn’t vary across various treatments. However, a
noticeable decline in available nitrogen content was observed in paddy soils beneath
mulberry, indicating its competitive nature. Tree species like Sesbania, red gram,
Cassia, Terminalia and Gliricidia, which demonstrate robust productivity and
resilience, are excellent choices for planting on wetland paddy field bunds. When
scaled to hectare basis, around 2 to 2.5 t/ha/year green leaf can be harvested from
500 plants of Sesbania/red gram accommodated on bund length of 500 m/ha (bunds
spaced at 20 m intervals in E-W direction), which can satisfy half of the
recommended green leaf manure doses in paddy.
The study also explored local farmers’ preferences and practices regarding
green leaf manuring. Traditionally, more than 15 tree species were utilized for green
leaf manure, primarily collected from forests (97.5% of farmers surveyed), with
species like Terminalia paniculata, Terminalia bellirica and Mangifera indica
being commonly employed. However, in the present scenario, the predominant
supplementary manures include cow dung (95%), green manure (40%), and green
leaf manure (preferably Gliricidia sepium and Mangifera indica) (70%). These
green leaf manures are often sourced from home gardens (62.5%) and field
boundaries (37.5%). Farmers have recognized the adverse impacts of chemical
fertilizers and demonstrated a strong interest in sustainable soil management.
Despite this interest, several challenges like labour scarcity, high cost, land
availability constraints, and transportation issues, hinder the widespread adoption
of green leaf manuring practices. Encouragingly, approximately 80 per cent of
farmers are interested in adopting green leaf manuring practices by planting green
manuring trees in unused areas, boundaries, and bunds. To support this transition,
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farmers actively seek technical support and subsidies from the Department of
Agriculture Development and Farmer’s Welfares

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