Influence of organic manure amendments on water repellency, water entry value, and water retention of soil samples from a tropical Ultisol

Abstract

Lowered stability of soil aggregates governed by insufficient organic matter levels has become a major concern in Sri Lanka. Although the use of organic manure with water repellent properties lowers the wetting rates and improves the stability of soil aggregates, its effects on soil hydrophysical properties are still not characterized. Therefore, the objective of this study was to examine the relation of water repellency induced by organic manure amendments to the water entry value and water retention of a Sri Lankan Ultisol. The soil was mixed with ground powders of cattle manure (CM), goat manure (GM), Gliricidia maculata (GL) and hydrophobic Casuarina equisetifolia (CE) leaves to obtain samples ranging from non-repellent to extremely water repellent, in two series. Series I was prepared by mixing GL and CE with soil (5, 10, 25, 50%). Series II consisted of 5% CM, GM, and GL, with (set A) and without (set B) intermixed 2% CE. Water repellency, water entry value, and water retention of samples were determined in the laboratory. Soilwater contact angle increased with increasing organic matter content in all the samples showing positive linear correlations. Although the samples amended with CE showed high soil-water contact angles in series I, set A (without 2% CE) and set B (with 2% CE) in series II did not show a noticeable difference, where >80% of the samples had soilwater contact angles <90°. Water entry value (R 2 = 0.83-0.92) and the water retention at 150 cm suction (R 2 = 0.69-0.8) of all the samples increased with increasing soil-water contact angles showing moderate to strong positive linear correlations. However, set A (without 2% CE) and set B (with 2% CE) in series II did not differ noticeably. Water entry value of about 60% the samples was <2.5 cm. Mixing of a small amount (2%) of hydrophobic organic matter with commonly used organic manures slightly increased the water repellency of sample soils, however not up to detrimental levels. It did not generate adverse effects on water entry and increased the water retention. It was clear that intermixing of small quantities of hydrophobic organic manure with organic manures commonly used in Sri Lankan agriculture, would not generate unfavorable impacts on soils.

Influence of Long‐term Application of Feedlot Manure Amendments on Water Repellency of a Clay Loam Soil

“…The WDPT findings (ESTIMATE comparison) indicated greater water repellency for amended than unamended soils, and the MED findings also suggested greater repellency at 39‐ and 77‐Mg ha −1 rates (but not 13 Mg ha −1 ) than the CON. Our finding that repellency was greater for amended than unamended soils for two of three methods was generally consistent with other studies that used WDPT and soil water contact angle methods (Pagliari et al, 2011; Leelamanie, 2014; Liyanage and Leelamanie, 2016).…”

“…Long‐term application of beef feedlot manure to cropland may influence repellency by increasing SOM and the proportion of hydrophobic carbon (C) compounds. However, there is little research on the influence of manure amendments on repellency (Pagliari et al, 2011; Leelamanie, 2014; Liyanage and Leelamanie, 2016). All previous studies were laboratory incubations with organic amendments applied only once to Alfisols, Entisols, or Ultisols, with no long‐term field studies on Mollisols.…”

“…However, inconsistent findings have been reported between repellency and quantity of SOM (Doerr et al, 2000). Greater application rates of feedlot manure to cropland may also influence soil repellency, since some studies have reported that soil water repellency increased with greater content of SOM (Doerr et al, 2000; McKissock et al, 2003; Ellerbrock et al, 2005; Leelamanie, 2014; Liyanage and Leelamanie, 2016).…”

“…The quality of organic matter may also be an important factor influencing soil repellency (Doerr et al, 2000; Ellerbrock et al, 2005; Cosentino et al, 2010). Manure may contain many different organic compounds that could potentially cause soil water repellency or hydrophobicity (Pagliari et al, 2011; Liyanage and Leelamanie, 2016). Soil water repellency has generally been attributed to two groups of soil organic C (Doerr et al, 2000).…”

Organic waste recycling in agriculture and related effects on soil water retention and plant available water: a review

“…Moreover, soil water retention is influenced by OM quality in terms of its wettability and its ability to retain water (Ojeda et al 2015). However, two recent studies (Ajayi et al 2016;Liyanage and Leelamanie 2016) adding hydrophobic organic amendments to soil under laboratory conditions both found increases in plant available water, which was ascribed to improved stabilization of aggregates allowing for better water retention (Liyanage and Leelamanie 2016).…”