Wood Vinegar and Calcium Boost Cotton Yield in Saline-Alkali Soils

Introduction

Soil salinization poses a major threat to agricultural productivity, particularly in arid and semi-arid regions. A recent study published in the *Journal of Soil Science and Plant Nutrition* explores the potential of combining pyroligneous solution (PS) and soluble calcium (Ca) to improve soil quality and enhance cotton (*Gossypium hirsutum*) growth under saline-alkali conditions.

Why Pyroligneous Solution and Soluble Calcium?

Pyroligneous solution (PS), also known as wood vinegar, is an organic liquid obtained from the condensation of gases produced during biomass pyrolysis. Rich in organic acids, phenols, and ketones, PS is known to reduce soil pH, modify soil ion composition, and promote microbial activity. Soluble calcium, on the other hand, plays a crucial role in stabilizing soil aggregates, counteracting the negative effects of sodium, and improving plant stress tolerance. This study examines whether their combined application can enhance soil health and cotton productivity in salt-affected soils.

Experimental Design and Application Methods

A pot experiment was conducted from April to October 2018 at Qingdao Agricultural University, China, using coastal saline soil. The researchers tested six treatments:

  • NF: No fertilizer (control)
  • TF: Conventional fertilization using compound fertilizer (750 kg/ha)
  • P0C0: No application of PS or Ca
  • P0C1: Application of 480 kg/ha of Ca
  • P1C0: Application of 240 kg/ha of PS
  • P1C1: Co-application of PS (240 kg/ha) and Ca (480 kg/ha)

The fertilizers and soil amendments were dissolved in irrigation water and applied through simulated drip irrigation at a rate of 120 m³/ha at key growth stages. Cotton seeds were planted in pots, with seedlings thinned at the five-leaf stage to ensure uniform growth.

Key Findings

Cotton Growth and Yield Improvements

  • Higher Biomass and Growth Metrics: The P1C1 treatment significantly increased fresh weight (by 182%), plant height (by 68.3%), and leaf width (by 53.0%) compared to P0C0.
  • Improved Seed Cotton Yield: The P1C1 treatment resulted in a 25.2% higher seed cotton yield than P0C0, demonstrating the benefits of co-application.
  • Photosynthetic Efficiency Gains: Quantum efficiency of PSII (ΦPSII) increased significantly, suggesting enhanced light energy conversion for photosynthesis.

Soil Quality Enhancements

  • pH and Electrical Conductivity (EC) Reduction: The P1C1 treatment decreased soil pH by 0.26 units and EC by 2.4 units compared to P0C0, improving soil conditions for plant growth.
  • Increased Soil Nutrients: The P1C1 treatment increased available nitrogen by 35.5%, phosphorus by 8.3%, and potassium by 14.8%, enhancing nutrient availability.
  • Enhanced Enzyme Activity: Urease, phosphatase, catalase, and sucrase activities significantly increased, indicating improved microbial function and soil fertility.

How the PS + Ca Combination Might Work

  • pH Regulation: The study observed that soil pH decreased slightly with PS application. This may be due to organic acids in PS neutralizing soil alkalinity, making nutrients more accessible to plants.
  • Salt Stress Alleviation: The study showed that calcium application reduced soil electrical conductivity (EC), which is associated with reduced salinity stress. It is possible that calcium replaced sodium in the soil, reducing sodium toxicity and improving soil structure.
  • Nutrient Mobilization: Increased enzyme activity in PS + Ca treatments suggests improved microbial function, which may contribute to nutrient cycling and better plant uptake. However, the specific mechanisms behind these changes were not detailed in the study.

Implications for Salt-Affected Agriculture

This study highlights the synergistic potential of PS and soluble calcium in improving soil properties and cotton yield in saline-alkali soils. While the individual application of either amendment provided some benefits, their combined use proved more effective at alleviating salt stress, enhancing photosynthesis, and increasing nutrient availability. Future research should investigate field-scale applications and long-term effects to further validate these findings.

Article based on: Combined Treatment of Pyroligneous Solution and Soluble Calcium Enhances Cotton Growth Through Improving Soil Quality in Saline-Alkali Soils