Effect of Different Fertilizer Application on the Soil Fertility of Paddy Soils in Red Soil Region of Southern China

Abstract

Appropriate fertilizer application is an important management practice to improve soil fertility and quality in the red soil regions of China. In the present study, we examined the effects of five fertilization treatments [these were: no fertilizer (CK), rice straw return (SR), chemical fertilizer (NPK), organic manure (OM) and green manure (GM)] on soil pH, soil organic carbon (SOC), total nitrogen (TN), C/N ratio and available nutrients (AN, AP and AK) contents in the plowed layer (0–20 cm) of paddy soil from 1998 to 2009 in Jiangxi Province, southern China. Results showed that the soil pH was the lowest with an average of 5.33 units in CK and was significantly higher in NPK (5.89 units) and OM (5.63 units) treatments (P<0.05). The application of fertilizers have remarkably improved SOC and TN values compared with the CK, Specifically, the OM treatment resulted in the highest SOC and TN concentrations (72.5% and 51.2% higher than CK) and NPK treatment increased the SOC and TN contents by 22.0% and 17.8% compared with CK. The average amounts of C/N ratio ranged from 9.66 to 10.98 in different treatments, and reached the highest in OM treatment (P<0.05). During the experimental period, the average AN and AP contents were highest in OM treatment (about 1.6 and 29.6 times of that in the CK, respectively) and second highest in NPK treatment (about 1.2 and 20.3 times of that in the CK). Unlike AN and AP, the highest value of AK content was observed in NPK treatments with 38.10 mg·kg−1. Thus, these indicated that organic manure should be recommended to improve soil fertility in this region and K fertilizer should be simultaneously applied considering the soil K contents. Considering the long-term fertilizer efficiency, our results also suggest that annual straw returning application could improve soil fertility in this trial region.

Responses of absolute and specific soil enzyme activities to long term additions of organic and mineral fertilizer

“…Results from our previous long-term monitoring suggest that swine manure and mineral fertilizer may increase soil acidity (Dong et al, 2012), which is in agreement with Steiner et al (2007). The positive relationships between soil pH and TP contents in this study confirmed that calcium-magnesium phosphate fertilizers could neutralize acidity in acid soils (Fig.…”

“…Based on similar amounts of P fertilizer, manure fertilizer contributed more to soil TP contents than the mineral fertilizer (Table 2). This is in agreement with long-term results from paddy soil trials (Dong et al, 2012;Wang et al, 2012). Organic manure contains a large amount of organic P, which will be released slowly, and will be beneficial to soil quality and crops over the longterm (Bi et al, 2009).…”

“…Redundancy analysis showed that changes in the composition of the soil microbial communities and soil environmental factors were important for maintaining soil enzyme activities. Our previous studies clearly demonstrated that swine manure could result in significantly increased contents of SOC and TN (Dong et al, 2012), and PLFAs, with increases in G + and actinomycetes (Dong et al, 2014), than the other treatments. This may help explain the enhanced effects of the swine manure on the hydrolytic enzyme activities and suggests that swine manure may promote secretion of hydrolytic enzyme activities by G + and actinomycetes.…”

“…The results of our previous study, in which substantial increases were observed in SOC, Gram-positive bacteria, and actinomycetes in red soils, highlighted the influence of swine manure or N, P, and K fertilizers on SOC contents and soil phospholipid fatty acid (PLFA) biomarkers in paddy soils (Dong et al, 2012(Dong et al, , 2014. However, there is a lack of information about the influence of fertilization practices on soil enzyme activities and their linkages with the structure of the soil microbial community in this region.…”

“…The positive responses of SOC, TN, and TP contents, soil microbial biomass, and absolute and specific enzyme activities to swine manure applications demonstrate that farmers should be instructed to reuse organic fertilizer on the reddish paddy soils (Dong et al, 2012(Dong et al, , 2014. Because of the inhibitory effects of N 2 P 2 K 2 and N 3 P 3 K 3 on AP absolute and specific activities and the potential risk of soil TP pollution, mineral fertilizer applications should be maintained below 338 (N)-44 (P)-140 (K) kg ha −1 year −1 .…”