The Humble Groundnut: More Than Just a Snack
Often called the peanut, groundnut (Arachis hypogaea L.) is far more than a simple snack food. This remarkable legume is a nutritional powerhouse, providing 26% protein, 12% starch, and essential minerals and fibers that make it vital for both human consumption and animal feed . As an oilseed crop, it plays a crucial role in global agriculture, particularly in semi-arid regions where other crops might struggle.
26%
Protein Content
12%
Starch Content
Key Crop
In Semi-Arid Regions
The challenge facing modern groundnut farmers lies in balancing productivity with sustainability. Like all crops, groundnut requires proper nutrition to thrive, but the sources of these nutrients—organic or inorganic—have become the subject of extensive scientific research. With groundnut production constrained by low soil fertility in many regions 2 , finding the optimal approach to nutrient management has never been more important for both yield and economic returns.
Organic vs Inorganic: Understanding the Nutrient Spectrum
The Organic Approach
Organic nutrient sources include materials like farmyard manure (FYM), castor cake, poultry manure, and vermicompost. These natural fertilizers do more than just feed plants—they improve overall soil health by enhancing its structure, water-holding capacity, and microbial activity.
One significant advantage of organic approaches is their ability to work in harmony with bio-inoculants like Rhizobium and Phosphate Solubilizing Bacteria (PSB). These microorganisms form symbiotic relationships with groundnut roots, helping convert atmospheric nitrogen into usable forms and releasing bound phosphorus in the soil 1 .
The Conventional Method
Inorganic fertilizers provide immediately available nutrients to plants in precise formulations. These include well-known compounds like urea (for nitrogen), single super phosphate (for phosphorus), and muriate of potash (for potassium) .
The primary advantage of these fertilizers is their predictable nutrient content and rapid action, allowing farmers to address specific nutrient deficiencies quickly. However, research has shown that continuous and imbalanced application of inorganic fertilizers can lead to soil degradation over time, reducing soil health and ultimately limiting groundnut productivity .
The Middle Path
A third approach, known as Integrated Nutrient Management (INM), combines the best of both worlds. This method uses a balanced combination of organic and inorganic sources, creating a synergistic effect that often yields better results than either method alone.
The INM strategy aims to achieve both productivity and sustainability with minimum production costs . Research has consistently shown that this integrated approach leads to higher yields, improved soil health, and better economic returns for farmers.
A Closer Look at the Evidence: Groundbreaking Research in India
To truly understand how nutrient sources affect groundnut cultivation, let's examine a comprehensive study conducted at the Agricultural College and Research Institute in Killikulam, India, during 2019 and 2020 .
Methodology and Experimental Design
Researchers established a field experiment using the groundnut variety TMV (Gn) 13 during the Rabi season (September to December). The soil was sandy clay loam with low organic carbon and medium available phosphorus—conditions representative of many groundnut-growing regions.
The experiment tested ten different treatments, combining various levels of:
- Soil Test Crop Response (STCR) recommended fertilizers (75% and 100% of 38:64:94 N-P₂O₅-K₂O kg/ha)
- Organic sources including poultry manure @ 3 t/ha
- Bio-inoculants (Rhizobium @ 3 kg/ha)
- Soil conditioners (Humic acid @ 20 kg/ha)
These treatments were arranged in a randomized block design with three replications to ensure statistical reliability .
Remarkable Findings: Beyond Expectations
The results revealed striking differences between the nutrient management approaches:
Growth Parameters: Plants receiving the integrated treatment of 75% STCR + Rhizobium + Humic acid + Poultry manure achieved the tallest height (67.2 cm) and required the fewest days to 50% flowering (31.1 days). This combination also produced the highest dry matter production (8,854 kg/ha) .
Yield Attributes: The integrated approach significantly outperformed other treatments in key yield components including pods per plant, hundred pod weight, and hundred kernel weight .
Groundnut Pod and Haulm Yield Under Different Nutrient Management Approaches
Economic Returns from Different Nutrient Management Strategies
| Treatment | Mean Pod Yield (kg/ha) | Mean Haulm Yield (kg/ha) | Net Returns (₹/ha) | Benefit-Cost Ratio |
|---|---|---|---|---|
| 75% STCR + Rhizobium + Humic acid + Poultry manure | 2,964 | 8,975 | 72,706 | 2.47 |
| 100% STCR (recommended fertilizers only) | 2,150 | 6,892 | 52,819 | 2.08 |
| Poultry manure only | 1,865 | 6,321 | 41,336 | 1.92 |
| Absolute control (no nutrients) | 1,423 | 4,856 | 19,452 | 1.45 |
Source: Adapted from Paramasivan et al., 2025
The Scientist's Toolkit: Essential Materials for Groundnut Research
Groundnut nutrient research relies on a diverse array of materials and reagents, each serving specific functions in evaluating plant growth and soil health:
| Research Material | Function/Purpose | Application Rate |
|---|---|---|
| Castor cake | Organic nutrient source, improves soil structure | 1.0 t/ha 1 |
| Poultry manure | Complete organic fertilizer, enhances microbial activity | 3 t/ha |
| Vermicompost | Organic amendment, improves soil fertility and structure | 2.5 t/ha 2 |
| Rhizobium inoculant | Biological nitrogen fixation, reduces N fertilizer requirement | 3 kg/ha |
| Phosphate Solubilizing Bacteria (PSB) | Makes phosphorus available to plants | Combined with Rhizobium 1 |
| Humic acid | Soil conditioner, improves nutrient uptake | 20 kg/ha |
| Zinc sulfate | Corrects micronutrient deficiency | 5 kg Zn/ha 2 |
| Agricultural lime | Corrects soil acidity, improves nutrient availability | 4 t CaCO₃/ha 3 |
Finding the Optimal Balance: What Research Reveals
Across multiple studies, a consistent pattern emerges: balanced combinations of organic and inorganic nutrients produce the best outcomes for groundnut cultivation.
Ethiopian Study
Research from Ethiopia demonstrated that the combined application of 46:46 kg N:P₂O₅ ha⁻¹ with 2.5 t vermicompost ha⁻¹ and 5 kg Zn ha⁻¹ produced the highest pod yield (3.13 t/ha), seed yield (2.16 t/ha), and oil content (51.3%) for the Ba-ha-Gudo variety 2 .
Acidic Soil Research
A study focusing on acidic soils in southwest Ethiopia found that the combination of 4 t lime ha⁻¹ and 46 kg P₂O₅ ha⁻¹ resulted in the highest pod yield (4.49 t/ha), oil content (50.6%), and protein content (33.1%) 3 .
Organic Systems
Even in strictly organic systems, research indicates that 1.0 t/ha castor cake combined with Rhizobium + PSB produced pod yields of 1,687 kg/ha—comparable to systems using FYM 5 t/ha + castor cake 0.5 t/ha with the same bio-inoculants 1 .
Economic Advantage
The integrated approach consistently demonstrates superior economic returns, with benefit-cost ratios exceeding 2.47 compared to 2.08 for inorganic-only and 1.92 for organic-only approaches .
Conclusion: Cultivating a Sustainable Future
The scientific evidence overwhelmingly supports integrated nutrient management as the most effective approach for summer groundnut cultivation. By combining 75-100% of recommended mineral fertilizers with organic sources like poultry manure, castor cake, or vermicompost, and enhancing these with bio-inoculants (Rhizobium, PSB) and soil conditioners (humic acid, lime), farmers can achieve:
- Higher pod and haulm yields
- Improved oil content and seed quality
- Better economic returns with benefit-cost ratios exceeding 2.47
- Enhanced soil health and long-term sustainability
As we face the dual challenges of increasing food production and preserving our agricultural resources, the thoughtful integration of organic and inorganic nutrient sources offers a scientifically-grounded path forward for groundnut cultivation and sustainable agriculture overall.