International Journal of Plant & Soil Science

Effect of Potassium Levels on Soil and Leaf Nutrient Status of Nagpur Mandarin (Citrus reticulata)

Pradeep K. Mitharwal — 2026-04-01

Potassium regulates enzymatic activities and stomatal movement, improving water-use efficiency and sugar transport within plants. Along with phosphorus, it supports rapid root growth and promotes protein synthesis. It also improves plant health and resistance to diseases, pests, and nematodes. Potassium deficiency reduces photosynthesis and yield, while excess nitrogen with low potassium can lead to poor fruiting and physiological disorders. The study highlights the significance of balanced and split potassium application along with foliar nutrition in enhancing macro- and micronutrient uptake, which is crucial for sustainable citrus production systems. A field experiment was conducted during 2022–23 at farmers’ fields in Pardi and Sawandri villages of Nagpur district on 10–12-year-old fruit-bearing orchards. The experiment included different potassium treatments and was laid out in a Randomized Block Design. Among all treatments, T₉ (RDF + 300 g K at BT (December) + 300 g K after 60 days + KNO₃ @ 1.5% spray after 90 days) was found significantly superior over other treatments. This treatment recorded higher leaf nutrient concentrations, including total nitrogen (2.19 and 2.29%), total phosphorus (0.099 and 0.123%), total potassium (1.40 and 1.46%), and total sulphur (0.24 and 0.23%) at Pardi and Sawandri villages, respectively. Similarly, total micronutrient content in leaves was also higher under this treatment, with iron (79.46 and 79.47 mg kg⁻¹), zinc (18.50 and 19.34 mg kg⁻¹), manganese (61.51 and 62.79 mg kg⁻¹), and copper (14.00 and 14.17 mg kg⁻¹) at Pardi and Sawandri, respectively. In addition, improved soil nutrient availability was observed with the same potassium treatment. The values recorded were nitrogen (322.50 and 331.30 kg ha⁻¹), potassium (498.19 and 435.32 kg ha⁻¹), iron (7.29 and 7.33 mg kg⁻¹), and zinc (0.86 and 0.84 mg kg⁻¹) at Pardi and Sawandri villages, respectively. Overall, the results indicated that the combined application of RDF with split doses of potassium and foliar spray of KNO₃ significantly enhanced both leaf nutrient status and soil nutrient availability in Nagpur mandarin orchards.

Agroforestry Shading Mitigates Light Stress in Cocoa (Theobroma cacao L.) by Improving Photosystem II Efficiency Assessed via Chlorophyll Fluorescence (Fv/Fm)

Guei Stéphane-Hubert — 2026-04-03

Background: Cocoa is a shade-tolerant species. Excessive light can induce photo-oxidative stress and photosystem II (PSII) photoinhibition in cocoa. In agroforestry, the tree canopy plays a key role in modulating the light microclimate and could therefore contribute to cocoa photoprotection.

Aims: This study evaluates the effect of different agroforestry shading levels on PSII efficiency, estimated from the maximum photochemical yield (Fv/Fm) measured after dark adaptation.

Study Design: Field experiment comparing three light environments on mature cocoa trees (O0: full sun; O1: moderate shade; O2: dense shade).

Place of Study: Experimental cocoa agroforestry sites in Côte d’Ivoire (Azaguie, Soubré, and Blé/Divo).

Methodology: Three light environments were implemented on mature cocoa trees: full direct light (O0), partial shade (approximately 30%, O1), and dense shade (30–60%, O2). The effect of shade on Fv/Fm was assessed using a Kruskal–Wallis test complemented by post hoc analyses (α = 5%).

Results: Shade had a significant effect on PSII efficiency (p-value = 0.009). Cocoa trees under full sunlight showed a reduced Fv/Fm ratio (0.752 ± 0.015), indicating strong photoinhibition, whereas trees under moderate shade (0.796 ± 0.003) and dense shade (0.785 ± 0.005) exhibited markedly higher values. O1 and O2 did not differ significantly, suggesting that a moderate shade level is sufficient to provide effective protection against light stress.

Conclusion: These results indicate that agroforestry shade reduces light stress in cocoa while increasing PSII performance. They highlight the value of moderate shade as a management approach to prevent photoinhibition. It is recommended that future studies should assess long-term yield and physiological resilience under optimised shade regimes.

Assessment of Farmers’ Knowledge on Soil Sampling Procedures and Soil Test Based Nutrient Management in Karimnagar District of Telangana, India

K. Madan Mohan Reddy — 2026-04-03

Soil testing and soil health card (SHC)-based nutrient management are pivotal components of sustainable agriculture. This study evaluated the knowledge level of 120 farmers in Karimnagar district, Telangana State, India, concerning soil sampling procedures and soil test-based fertilizer recommendations. Employing an ex-post facto research design with a pre-tested structured interview schedule, data were collected and analysed using descriptive statistics and Pearson's correlation coefficient. The findings reveal that a majority of respondents (60%) possessed a medium level of knowledge, while 24.17% demonstrated high knowledge and 15.83% showed low knowledge. The highest awareness was recorded for the availability of soil testing services (88.33%), the need to apply nitrogen in three split doses in paddy (87.50%), and the role of balanced fertilization in maintaining soil health (85.83%). Conversely, knowledge gaps were most pronounced concerning the recommended zinc sulphate dose for correcting zinc deficiency in paddy (56.67%), the prescribed quantity of muriate of potash for paddy (58.33%), and the variation of fertilizer dose for paddy with soil test values (57.50%). Correlation analysis identified education (r = 0.462**), training undergone (r = 0.518**), extension contact (r = 0.487**), scientific orientation (r = 0.436**), and innovativeness (r = 0.401**) as highly significant predictors of knowledge at the 1% level. Farm size (r = 0.298*), economic motivation (r = 0.321*), and achievement motivation (r = 0.354*) were significant at the 5% level. Age and farming experience did not exhibit significant relationships with knowledge. These results underline the critical need for targeted extension training, field demonstrations, and digital outreach to bridge knowledge gaps and enhance adoption of soil test-based nutrient management among farming communities.

A Review of Modern Soil pH Monitoring Techniques and Their Effects on Crop Yield

Battala Sheshagiri — 2026-04-03

Soil pH is a fundamental determinant of soil fertility, nutrient availability, and crop productivity. It influences chemical equilibria, microbial processes, and plant nutrient uptake, making it a key factor in sustainable agricultural management. Conventional soil pH measurement techniques, such as laboratory-based glass electrode methods, although accurate, are often labor-intensive, time-consuming, and inadequate for capturing spatial variability within fields. With the advancement of precision agriculture, modern soil pH monitoring technologies have emerged, offering real-time, high-resolution, and site-specific data.

This review comprehensively examines recent developments in soil pH monitoring techniques, including electrochemical sensors, optical and spectroscopic approaches, proximal and remote sensing, and IoT-based systems integrated with machine learning algorithms. These technologies have significantly improved the efficiency of soil monitoring, enabling farmers to optimize nutrient management and enhance crop yield. The integration of artificial intelligence and wireless sensor networks has further facilitated predictive modeling and automated decision-making.

The relationship between soil pH and crop yield is critically analyzed through multiple case studies, demonstrating how precise pH management can enhance nutrient use efficiency, reduce environmental impacts, and increase productivity. Despite these advancements, challenges such as sensor calibration, cost constraints, and environmental variability persist. Future prospects include the development of low-cost sensors, AI-driven decision support systems, and fully automated smart farming solutions. This review highlights the transformative role of modern soil pH monitoring in achieving sustainable agriculture and global food security.