Optimizing P and Zn Levels for Greengram Growth: Insights into P-Zn Interaction and Rhizospheric Soil pH

Aims: Phosphorus (P) and zinc (Zn) are essential nutrients for plant growth, and their interaction can significantly influence nutrient uptake and crop productivity. Understanding the optimal balance between P and Zn is crucial for efficient fertilization strategies, especially in soils with low P status. This study aimed to investigate the impact of P-Zn interaction on greengram growth and its relationship with rhizospheric soil pH.

Materials and Methods: A pot experiment was conducted using red and lateritic soil, with 21 treatments consisting of different levels of P and Zn. Greengram (Vigna radiata L.) plants were subjected to these treatments, and after 28 days, measurements were taken for dry weight, P and Zn content in shoots, and rhizospheric soil pH.

Results: After 28 days of seeding, strong P-Zn interactions were observed in the soil-plant system, significantly affecting greengram growth, as well as Zn and P accumulation, and rhizospheric soil pH. High P addition resulted in a significant decrease in Zn content, while the dosage of Zn had minimal impact on P content. Interestingly, Zn treatment without P addition did not enhance dry matter. However, increasing Zn levels with P addition up to 200 mg kg-1 soil improved crop growth. Beyond this threshold, yields started to decline, potentially due to P toxicity and/or Zn deficiency. Surprisingly, excessive inorganic P addition increased the rhizospheric soil pH, which could potentially reduce Zn uptake and subsequently elevate the P-Zn molar ratio in the shoot.

Conclusion: This study demonstrates that understanding the optimal doses of P and Zn and their influence on nutrient absorption and rhizospheric soil pH is crucial for sustainable crop production. The findings provide valuable insights for designing effective fertilization strategies in P-deficient acid soils to improve greengram productivity while maintaining nutrient balance.