A Long Term PAM Application on Soil Microbial Biomass and Oat (Avena nuda L.) Growth in Loess Hilly-Gully Region of China

Abstract

Abstract. Effects of different years of Polyacrylamide (PAM) application on oat growth, soil microbial biomass and moisture content in semi-arid regions were studied through a field experiment from 2011 to 2015. The experiment consisted of total of 5 treatments and a control. These were: Conventional tillage (CK), (1) M1: PAM 2011, (2) M2: PAM 2011 and 2012, (3) M3: PAM 2011, 2012, (4) M4: PAM 2011, 2012, (4) M5: PAM 2011, 20122015and 2015. The results showed that with increasing PAM and the time interval, the oat seedling soil moisture content (SMC), microbial biomass carbon (SMBC), microbial biomass nitrogen (SMBN), and microbial biomass phosphorus (SMBP) had a rising trend. Compared with the control, the treatments administered continuously for five years; SMC of 0-60 cm soil layer was affected the mostly. Differences of test groups decreased with the increase of soil layer. At a depth of 0-60 cm soil, soil moisture increased by 25.91-78.51% in M5. SMBC increased by 21.39-69.49% in M4, SMBN increased by 34.58-139.02% in M5 and SMBP increased by 44.58-83.38% in M5. Meanwhile, aboveground fresh weight increased by 196.67-232.88% in M5 as well as dry weight increased by 182.05-224.23% in M5, respectively after stable emergence. The effects of applying PAM on micro ecological with differences time interval have an effect on soil microbial life, the results point out the following superiority order: 5 years>4 years>3 years>2 years >1 year. However, there was significant improvement observed in plowing layer, with continuous application of PAM at 0-20 cm depth, SMC has significant positive correlations with fresh biomass and all three SMB variables. We recommend application of PAM could improve soil moisture content and then influence microbial biomass and further plant growth; M5 treatment which is more suitable for the rainfed farmland. Farmers can be recommended to use PAM to improve soil qualities and crop production in loess hilly-gully region of China.