Effect of weed composts as an integrated nutrient source on productivity and yield components of Maize (Zea mays L.) in a maize-groundnut cropping system

Introduction

Modern agriculture faces the dual challenge of sustaining food production while maintaining soil health. The continuous and imbalanced use of chemical fertilizers has led to a decline in soil fertility and stagnation in crop productivity. Simultaneously, the proliferation of invasive weeds such as Parthenium hysterophorus, Chromolaena odorata and Eichhornia crassipes poses a significant threat to ecosystems and agriculture. Converting this huge weed biomass into compost offers a unique opportunity to address both issues. Weeds are often rich in nutrients and can serve as a valuable source of organic matter. Chromolaena and Parthenium, for instance, accumulate significant amounts of nitrogen, phosphorus and potassium in their tissues. Previous studies have shown that weed utilization as compost can improve soil physical, chemical, and biological properties, favouring better crop growth. This study investigates the efficacy of utilizing composts prepared from four specific weed species to substitute inorganic nitrogen in maize cultivation, aiming to identify a sustainable integrated nutrient management strategy.

Materials and Methods

Experimental Site and Design

The experiment was conducted during the Kharif seasons of 2009 and 2010 at the Main Research Station (MRS), Hebbal, Bengaluru. The soil was red sandy loam with a pH of 6.8, available nitrogen (N) of 294.2 kg ha -¹, available phosphorus (P 2 O 5 ) of 30.5 kg ha -¹ and available potassium (K 2 O) of 210.1 kg ha⁻¹. The experiment adopted a Randomized Complete Block Design (RCBD) with 14 treatments and three replications.

Treatment Details

The treatments included varying levels of RDF combined with 25% N substitution through different composts: T 1 -25%

Compost Preparation

Fresh biomass of Chromolaena, Parthenium, Cassia and water hyacinth was collected before seeding for compost preparation for the maize-groundnut cropping system experiment conducted at Hebbal. Green biomass of Parthenium and Cassia was collected from farm surroundings, wastelands and roadsides, Chromolaena from the forest ecosystem around GKVK and water hyacinth from the nearby Hebbal Lake prior to flowering. Cow dung obtained from the dairy farm, UAS, Hebbal, Bengaluru, was used to prepare slurry in a 1:2 ratio (cow dung:water), which served as an additive. Microbial inoculum consisting of Pleurotus sajor-caju, Phanerochaete chrysosporium and Trichoderma harzianum was procured from the Department of Agricultural Microbiology, UAS, GKVK, Bengaluru. Compost treatments included Chromolaena (C1), Parthenium (C2), Cassia (C3) and water hyacinth (C4), each combined with cow dung slurry at 20 per cent and microbial culture at 5 kg tonne⁻¹ of organic material. For composting, about 500 kg of fresh biomass of each weed was chopped into 2-3 inch pieces and composted separately in pits of 4 × 3 × 3 ft dimensions by layering 100 kg biomass in 15-20 cm thickness, followed by uniform application of 10 kg cow dung slurry and microbial inoculum per layer, repeated until the pit was filled up to 15 cm above ground level. The pits were covered with 1-2 cm thick red earth and moisture content was maintained at 50-60 per cent by periodic watering. Turning of composting pits was carried out at 30, 45 and 60 days to enhance aeration, temperature, uniform mixing and decomposition, and fully matured, pleasantly odour composts were obtained after 90 days.

Results and Discussion

The integration of weed composts with 100% Recommended Dose of Fertilizers (RDF) resulted in consistently higher cob lengths (16.4-16.9 cm) compared to 100% RDF alone (14.1 cm). The maximum cob length (16.9 cm) was recorded in the Cassia compost + 100% RDF (T 6 ) treatment.

Yield attributes

A similar trend was observed for the number of kernels per cob. The treatment 10 t FYM + 100% RDF (T 11 ) recorded the highest value (595.3), which was statistically on par with Chromolaena compost + 100% RDF (T 2 ) at 579.4 and FYM + 100% RDF (T 10 ) at 577.6. Regarding 100-seed weight, the highest value was recorded in T 11 (38.0 g), followed by T 2 and T 10 (both at 36.5 g).

Discussion

The significant enhancement in maize productivity through the integrated use of weed composts and chemical fertilizers can be attributed to the "priming effect", where organic amendments improve the physical environment of the soil, thereby increasing the efficiency of inorganic fertilizers. The high performance of Chromolaena odorata and Cassia composts (T 2 and T 6 ) is supported by Quansah et al. (2001) [7] , who found that these species possess high nitrogen and phosphorus concentrations with rapid decomposition rates, ensuring a steady nutrient supply during the critical silking and grain-filling stages. Similarly, the effectiveness of Parthenium compost (T 4 ) aligns with Kishor et al. (2010) [9] , who reported that Parthenium serves as a rich source of micronutrients and improves soil enzyme activities, leading to better kernel development.

The observation that 75% RDF + Weed Compost outperformed 100% RDF alone highlights a significant fertilizer-saving potential. According to Dilshad et al. (2010) [6] , organic matter enhances the cation exchange capacity (CEC) of the soil, reducing nutrient leaching and improving the translocation of photosynthates from the source (leaves) to the sink (kernels). This is reflected in the significantly higher 100-seed weight observed in compost-treated plots. Furthermore, the parity between weed composts and traditional FYM (T 11 ) is consistent with Ramesh et al. (2009) [8] , who argued that diverse organic sources can effectively maintain soil quality and yield levels in Indian cropping systems. The successful utilization of Water Hyacinth (T 8 ) further demonstrates the potential of converting problematic aquatic weeds into nutrient-rich amendments, as found by Lata and Veenapani (2011) [10] , who noted its ability to improve soil porosity and moisture retention.

Conclusion

The study demonstrates that invasive weed species such as Chromolaena odorata, Parthenium hysterophorus, Cassia spp. and water hyacinth can be effectively converted into compost and utilized as nutrient sources in maize cultivation. Substitution of 25% of mineral nitrogen with weed-based compost maintained yields comparable to the standard FYM application and significantly outperformed the sole use of chemical fertilizers. This approach provides a dual advantage of managing invasive weed biomass while reducing dependence on inorganic fertilizers.

The integration of weed-based composts with chemical fertilizers proved to be an effective strategy for enhancing maize productivity and yield attributes. The key findings of the study are summarized as follows:

• Superiority of integrated nutrient management: Application of 25% nitrogen through weed composts (particularly Chromolaena, Parthenium, and Cassia) in combination with 100% RDF consistently produced superior yield attributes, including cob length, number of kernels per cob, and seed weight, compared to the application of 100% RDF alone. • Productivity benchmarks: The treatment comprising 10 t FYM ha⁻¹ combined with 100% RDF recorded the highest kernel yield (6,301 kg ha⁻¹) and stover yield (9,023 kg ha⁻¹). However, treatments involving weed composts (T 2 , T 4 , and T 6 ) were statistically comparable to this standard practice. • Fertilizer-saving potential: A notable outcome of the study is the possibility of reducing chemical fertilizer use by 25%. Treatments receiving weed composts along with 75% RDF (e.g., T 5 ) produced significantly higher yields than the 100% RDF-alone treatment, indicating improved fertilizer use efficiency through organic amendments. • Resource valorization: Composting invasive weeds such as Chromolaena odorata, Parthenium, and water hyacinth serves as a sustainable and cost-effective nutrient source for farmers while offering an environmentally sound approach to managing problematic weed biomass.

References

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