Effect of long-term (13 years) application of different quality plant residues on soil organic carbon and soil properties of a sandy soil of northeast Thailand

Abstract

We studied the effects of long term (13 years) annual applications of different quality organic residues on physical and chemical properties of an upland sandy soil as related to soil organic C (SOC) accumulation. At the end of year 13, SOC accumulation was highest in tamarind litter (intermediate contents of N, lignin (L) and polyphenol (Pp)) (8.41 Mg ha-1) treatment, followed by the dipterocarp leaf litter (low N, high L and Pp), groundnut stover (high N, low L and Pp), and rice straw (low N, L and Pp but high cellulose), which were 7.06, 7.10 and 5.54 Mg ha-1, respectively. Application of plant residues significantly reduced soil bulk density (Db) and increased mean weight diameter (MWD) (0.25-0.30 mm) over the control (0.21 mm). The infiltration rate under plant residues addition (1.54-2.87 cm min-1) was higher than the control treatment (0.97 cm min-1). In addition, the effective CEC (ECEC) was 2-5 times higher under the plant residue treatments than the control (1.58 cmol kg-1). ECEC was highest under intermediate quality residue, like the tamarind but lowest under the rice straw. The SOC content was negatively correlated with Db (R2= -0.49**) but was positively correlated with MWD (R2= 0.57**), and ECEC (R2= 0.89***). We concluded that long-term continuous application of organic residues especially those with intermediate contents of N, L and Pp, like tamarind, led to increase SOC accumulation, which, in turn, improve physical and chemical properties of tropical sandy soils.