ABSTRACT
Long-term fertilization has an important effect on soil fertility and soil microbial activity. In order to explore the effects of long-term fertilization on soil extracellular enzyme activities and nutrient characteristics in a terrace on the Loess Plateau, we based our investigation on the long-term nutrient localization plot of Ansai Soil and Water Conservation Experimental Station, Chinese Academy of Sciences. We measured the soil physicochemical properties, microbial biomass, and extracellular enzyme activities of six fertilization treatments, which included no fertilization (CK); manure and nitrogen fertilization (MN); manure and phosphate fertilization (MP); manure, nitrogen, and phosphate fertilization (MNP); manure (M); and nitrogen and phosphate fertilization (NP). The results showed that all fertilization treatments significantly increased soil nutrient content and soil extracellular enzyme activities compared with that in CK. Correlation analysis showed that extracellular enzyme activity and soil physicochemical properties had an extremely significant correlation. The redundancy analysis indicated that soil nutrient and soil microbial biomass could explain 79.66% and 74.87% of the variation in soil extracellular enzyme activity and its stoichiometric ratio, respectively. Thus, the effects of fertilization on soil fertility were primarily through influencing soil extracellular enzyme activities indirectly. M, MN, MP, and MNP significantly improved soil organic carbon (SOC); soil total nitrogen (STN); and carbon (C), nitrogen (N), and phosphorus (P) source enzyme content; however, MNP changed the soil pH, which had an inhibitory effect on microbial activities. Vector analysis showed that the microbial communities of all treatments were in the condition of P limitation. Although MNP could alleviate the extent of P limitation, there was no significant difference between M and MP. Our study indicated that long-term application of manure[7500 kg·(hm2·a)-1]could meet the nutrient requirements of dryland crop growth, and long-term application of manure combined with phosphorus fertilization could alleviate the resource constraints faced by microorganisms. Consequently, our results provide a new insight into improving regional nitrogen excess.
Subject(s)
Fertilizers , Soil , Agriculture , Carbon , Fertilization , Fertilizers/analysis , Manure , Nitrogen/analysis , Nutrients , Phosphorus , Soil MicrobiologyABSTRACT
The matching of root system is a key factor driving the resistance of plant community to soil erosion. In this study, Amoeba graphical method was used to establish a root framework erosion resistance index (ERIrf, %) from three dimensions of root morphology, quantity and spatial concerns to quantify the effective of root erosion resistance by plant community. We analyzed root growth characteristics of plant community from abandoned land, Caragana korshinskii and Robinia pseudoacacia communities in loess hilly area. The results showed that the parameters of constructing the root framework erosion resistance index included the acting coefficient of root framework (α), root density (Rb, kg·m-3), root framework degree (S), soil bulk density (ρ, g·cm-3), and soil and water conservation coefficient (φ). The equation could be expressed as ERIrf=α×Rd×S×φρ×100%. This root framework erosion resistance index well represented the erosion resistance effects of plant root system. Logarithmic function could better fit the relationship between soil erosion resis-tance ability and root framework erosion resistance index. Our findings would provide scientific reference for the construction of anti-erosion vegetation community and assessment of ecological construction.
Subject(s)
Caragana , Robinia , China , SoilABSTRACT
Soil enzymes are catalysts for organic matter decomposition, the kinetic characteristics of which are important indicators of the catalytic performance of enzymes, with important role in evalua-ting soil health quality. We examined the responses of soil enzyme kinetic parameters to temperature change and the variation characteristics of their temperature sensitivity (Q10) in Robinia pseu-doacacia plantation soil under three different vegetation zones on the Loess Plateau. The results showed that the potential maximum reaction rate (Vmax) and the half-saturation constant (Km) of alanine transaminase (ALT), leucine aminopeptidase (LAP) and alkaline phosphatase (ALP) all increased linearly with the increasing incubation temperature. The zonal regularity of forest zone > forest-steppe zone > steppe zone was presented in Vmax. The temperature sensitivity of Vmax(Q10(Vmax)) ranged from 1.14 to 1.62, and the temperature sensitivity of Km(Q10(Km)) ranged from 1.05 to 1.47, with both values being lower in forest-steppe zone than other vegetation zones. In low and high temperature regions, the variations of Q10 in different soil enzymes differed among vegetation zones. Results from redundancy analysis showed that Q10 had a significant correlation with environmental variables, especially soil nutrients, indicating that Q10 would be affected by other environmental factors besides temperature.
Subject(s)
Robinia , Carbon/analysis , China , Nitrogen/analysis , Phosphorus/analysis , Soil , TemperatureABSTRACT
Hydrated ferric oxide was successfully impregnated onto tea waste by precipitation to obtain a new sorbent named HFO-TW, the adsorption characteristics of which toward Pb(II) in aqueous solution was investigated by evaluating the effects of pH value, contact time, coexisting ion, temperature, and initial concentration of Pb(II). The Pb(II) sorption onto HFO-TW was pH- dependent, and the higher pH value was more helpful for Pb(II) adsorption onto HFO-TW in the pH range of 2.5-7. Lead sorption speed was quick and could reach equilibrium within 100 min, and the kinetics curve could be fitted well by both pseudo-first and pseudo-second models. The related coefficient was 98.8%. HFO-TW exhibited highly selective lead retention and the adsorption capacity of Pb(II) onto HFO-TW was declined by only 12.1 mg · g(-1) and 8.1 mg · g(-1) in the presence of competing Ca(II), Mg(II) at 50 times of the target ion. In addition, Pb(II) sorption onto HFO-TW could be described satisfactorily by Langmuir model, and the maximal sorption capacity calculated by Langmuir equation was 89.43 mg · g(-1), which was much higher than the unmodified tea waste and other bio-sorbents. All the results validated that HFO-TW was a promising sorbent for removal of lead from waters.