The concept of bio-economic mulching in droughty tropical agroecosystems and its trans-season effects on soil hydro-thermal regime and okra performance

Abstract

<p>Mulching is an effective soil-water conservation technique in high-evaporative-demand tropical climates. Because of the drawbacks in bulk application of organic mulches, we introduce the concept of bio-economic mulching (BEM), a one-time low-rate application of organic mulch to improve soil productivity while sustaining economic viability. The study evaluated the effects of BEM (dry-grass mulching at 0, 2, 4, and 6 t ha<sup>–1</sup>) on soil hydrothermal properties of sandy-loam Ultisols using okra growth during 4–9 weeks after sowing in successive rainy-to-dry/partially rainfed season (PRS) and rainy/completely rainfed season (CRS). During the PRS, soil volumetric moisture content (<em>q</em>) increased (10.02%–25.50%), but soil temperature decreased (37.67–26.67°C) as BEM rate increased. A similar <em>q</em> trend (8.71%–18.37%) occurred during the CRS. Soil thermal conductivity (0.78to 4.88 W m<sup>–1 </sup>K<sup>–1</sup>), thermal diffusivity (3.95 × 10<sup>–7</sup> to 35.97 × 10<sup>–7</sup> m<sup>2 </sup>s<sup>–1</sup>), and heat flux (15.00 to 85.56 W m<sup>–2</sup>) generally decreased as <em>q</em> increased with BEM application rate particularly during the PRS; the reverse prevailed for volumetric heat capacity (1.33 × 10<sup>6 </sup>to 2.25 × 10<sup>6</sup> J m<sup>–3 </sup>K<sup>–1</sup>). Okra plant height differed (BEM-6 > BEM-4 > BEM-2/BEM-0) in the PRS, but BEM-6 and BEM-4 gave the tallest and shortest plants, respectively in the CRS. Fruit yield was 1.8- and 9.5-fold higher in BEM-6 than BEM-4 in PRS and CRS, respectively. Mulch treatment-induced temporal variations in soil <em>q</em> influenced okra performance indices of plant height (<em>r<sup>2</sup></em> = 0.85) and total fresh fruit yield (<em>r<sup>2</sup></em> = 0.69). In droughty tropical environments, BEM implementation at 6 t ha<sup>−1</sup> could engender soil hydrothermal regime favoring vegetable production beyond the ‘drier’ first season and even more pronouncedly in the second season.</p>