Impact of soil solarization on the ciliate community structure of a greenhouse soil

Abstract

Soil solarization is an ecologically friendly method of controlling various plant pathogens and pests, but also affects non-pathogenic members of the soil biota. Here, we studied the impact of soil solarization on the community structure of soil ciliates using a culture-independent molecular approach, namely denaturing gradient gel electrophoresis (DGGE) of targeted 18S rRNA gene fragments. Greenhouse soil with added organic fertilizers was solarized for 33 days at an average temperature of 47-48°C. Solarization caused a drastic change in the ciliate community. The variation between replicates was large, which suggested that the distribution of ciliates was spatially heterogeneous in the soil, probably due to their decreased numbers. In contrast, non-solarized soil had a stable and homogeneous ciliate community during the experimental period. In solarized soil, most of the original ciliate community recovered 76 days after solarization. Sequence analysis of DGGE fragments indicated that both r-selected and K-selected species of ciliates were affected by solarization but recovered with time after solarization. Our results demonstrated both the vulnerability and resilience of the ciliate community to soil solarization and also the utility of using molecular-based analysis of ciliate communities as bioindicators of soil stress caused by solarization.

Fluctuations in the abundance of ammonia oxidizers and the contents of inorganic nitrogen in solarized soil

“…The soil conditions with relatively high contents of ammonium-N ( Figs. 1 and 2) and near neutral pH values (5.9-7.4, Murase et al 2015;Yokoe et al 2015) would have excluded major contribution of AOA to ammonia oxidation of the soils in the present study. Small fluctuation in the copy number of amoA gene except for the bed C of NUF (Fig.…”

“…The site was the same as that in the previous study (Murase et al 2015), but in a different greenhouse from the previous one. The soil was Typic Fluvaquent and the pH (H 2 O) was 6.0.…”

“…Three plots with a randomized arrangement in triplicate (3.53 m 2 each) were used: plots applied with liquid fertilizer prepared from distillery waste treatment of barley shochu (1 × 10 4 kg ha −1 [fresh weight], N-P 2 O 5 -K 2 O = 2.0-0.6-0.4%; Japanese liquor; Unkai Shuzo Co. Ltd., Miyazaki, Japan) before solarization (on 18 July, Sb) and after solarization (on 29 August, Sa) and the control plot (NS) applied with the liquid fertilizer (1 × 10 4 kg ha −1 [fresh weight]) on 29 August 2014. The solarization treatment was conducted for 33 days from 18 July to 20 August as explained in detail by Murase et al (2015). The treatment with a laminated aluminum sheet to prevent elevation of temperature was performed for the plot NS in the similar procedure and the plot NS was designated as a non-solarized plot.…”

Quest of Soil Protists in a New Era

“…Fertilization can shape the structure of soil microbial food web ( 41 , 48 ). Heat stress dramatically disturbs the ciliate community in the greenhouse soil ( 49 ).…”