Speaker: Girija R
The main objective of the study was to evaluate the effect of different faecal-sludge-based inputs (treated faecal sludge, co-composted faecal sludge (FS)) and non-faecal sludge-based inputs (farmyard manure, chemical fertilizers) on the growth of weeds (unwanted plants) in the crop field. For this, a field experiment for two cropping seasons was conducted. Based on findings from the field, the study recommends best practices for application of faecal sludge-based inputs in agriculture. The study findings recommend assessing the impact of faecal sludge-based inputs on the final produce and soil ecosystem for future work.
An increasing population is leading to the depletion of natural resources and putting stress on how we manage them. Primarily because our ability (to manage these resources) is not up to speed with the growth of the population. This is leading to issues like sanitation and hunger. The situation is more serious in countries like India, where a majority of the population is undernourished – a result of poor sanitation and resources constraints for crop cultivation as well as the increased cost of food production.
The Nexus intervention of excreta sludge management (Circular economy approach) for improved nutrition and hygiene can help address both hunger and under-nourishment. On one hand, it would improve the sanitation situation, creating a conducive environment for digestion; while on the other hand, it increases the supply of quality food by using nutrient-rich wastewater and treated faecal sludge for food production.
Faecal Sludge Management (FSM) has been emerging as a mainstream solution to provide safe sanitation to the majority (especially relevant for India where 70% of households are dependent on Onsite Sanitation Systems). A key part of Faecal Sludge Management is treatment of Faecal Sludge, which can lead to by-products like dried FS, biochar and co-composted FS.
By safely treating FS and producing nutrient-rich compost, FSM closes the nutrient loop, showing potential to solve the problem of sanitation as well as hunger. While a few studies have been conducted to evaluate the impact of using faecal sludge (FS) inputs in food production, (to the knowledge of the author) limited studies have been conducted to understand the implications of using FS inputs on the growth of weeds and crop residues.
In this context, a study was conducted at the Faecal Sludge Treatment Plant (FSTP) at Devanahalli (near Bengaluru, Karnataka, India) with two specific objectives. One was to evaluate the effect of application of different faecal sludge-based inputs (treated faecal sludge, co-composted faecal sludge) and non-faecal sludge-based inputs (farmyard manure, chemical fertilizers) on crop yield, growth and development; the other to evaluate the effect of these nutrient sources on the growth of weeds. This paper discusses on the latter objective. The study also evaluated the impact on vegetative growth of crop residues i.e. plant residues left after the harvest.
Co-composted faecal sludge was obtained from the FSTP by composting treated FS with wet waste collected from the town. Randomised Block Design (RBD) methodology was followed. The field experiment included 20 blocks/plots in total with 5 treatments or nutrient sources and 4 replications of each of these treatments. Field experiments for two cropping seasons were conducted. A high growing crop - Field Beans - was grown during the monsoon season; and a root crop - Sweet Potato - was grown during the winter season. Data from the field experiments was collected and analysed for both seasons. The weight of weed plants from the faecal sludge applied plots were higher compared to other plots for both the seasons; while the weight of weed plants from co-compost applied plots was lower for both the seasons.
The study findings have shown that the plots grown under treated FS had more weed growth compared to other nutrient sources. Increased weed growth is attributed to the nutrient content of the FS (rich in Nitrogen). Unlike chemical fertilizers, where nutrients are applied in quantities as per crop requirement, measuring amounts of nutrient content when applying FS is not possible. Since FS is rich in one or more major nutrients, its application results in excess or deficiency of one or more major nutrients. This is what leads to the growth of unwanted plants/weeds.
However, weed growth was less in the case of co-composted plots (compared to other plots). This is because it is possible to achieve a nutrient balance while co-composting. FS, which is rich in nitrogen, is co-composted with organic waste, which is rich in carbon, hence achieving a balanced C: N (Carbon: Nitrogen) ratio. The study thus recommends the application of co-composted faecal sludge for crop production (to avoid weed menace that is common when FS alone is applied). In order to arrive at a definitive conclusion, the study proposes repeating the field experiments for a few more cropping seasons and for a different set of crops.
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