Effect Of Conservation Tillage On Soil Respiration And Soil Moisture For Maize/wheat Rotation In The North China Plain

The quantity of carbon in the soil is higher than the total of carbon in the atmosphere and terrestrial vegetation together. Adequate change in soil management can improve soil quality, reduce soil carbon dioxide(CO2) emission, and therefore, decreases atmospheric CO2 concentration. Soil organic carbon is also one of the important soil properties which is involved in soil function for soil productivity. The tillage practice can influence soil organic carbon, soil moisture, bulk density, and soil fertility. However, the mechanisms behind soil organic carbon decomposition are still not totally known, and the results of research vary. Tillage increases the availability of soil organic carbon and residues for the microorganisms. In addition, fertility and soil organism activity are also affected by the change in soil moisture, bulk density, and soil temperature.The objectives of this study were to examine the effects of tillage practice on soil respiration, soil moisture, temperature, organic carbon and bulk density. It also examined the changes in soil total nitrogen. In order to achieve these objectives, field experiments was conducted in North China plain and the treatments were five tillage practices – conventional and conservation: Rotary tillage without crop residues was conventional tillage(CT). However, rotary tillage with straw incorporated into the soil(RS), rotary tillage with crop residues incorporated into the soil in winter, and no-tillage with crop residues used as mulch in summer(TWS), rotary tillage with crop residues incorporated into the soil in summer and no-tillage with crop residues used as mulch in winter(TSS), and no tillage with crop residues used as mulch(NTS) were conservation tillage. Each treatment was repeated three times. Soil respiration was measured with a LI-8100 and the gravimetric method was used to determine soil water content at 0-200 cm with 20 cm of increment. Soil temperature at 5 cm depth also was measured directly by Li- 8100 with a temperature sensing probe during the CO2 measurement time. The crops were winter wheat(Triticumaestivum L) and summer maize(Zea mays L). Soil bulk density(BD, gcm-3) was determined by using the cutting ring core method at the depth of 0-20 cm. For soil organic carbon and soil total nitrogen determination, Dichromate oxidation method and Kjeldahl method were used respectively.During maize growing period NTS significantly decreased soil respiration by 36.48%, 24.81%, 8.68%, and 7.2% compared with TWS, RS, TSS, CT, and NTS respectively. During the wheat growing period, NTS significantly decreases soil respiration by 32.40% and 26.83 % compared with TWS and RS respectively, however, NTS significantly increased soil respiration by 27.57% and 23.55% compared with CT and TSS respectively. At 20 cm depth, average soil water content was significantly ranked as follows: RS = TWS > CT = TSS > NTS during wheat maize growing period, and for maize the same rank was observed, however significant difference was observed between RS and TWS and, no significant difference was obtained between TSS and NTS.In 2015, soil bulk density significantly(p < 0.05) was in this order: CT > NTS = TWS > TSS > RS. For soil organic carbon content, CT significantly had the lowest value and no significant difference wasobserved among other treatments. In addition, NTS significantly increased soil TN by 45.39%,23.19%, 20.18%and 13.11% compared with CT, RS, TWS and TSS. Furthermore, NTS significantly had the highest available phosphorus content.During both wheat and maize growing period, soil respiration was exponential related to soil temperature, and polynomial or no relationship was observed between soil water content and soil respiration. Soil respiration was simultaneously explained by both soil moisture and soil temperature.