Effects of straw incorporation and N fertilization on soil respiration during maize (Zea mays L.) growth in Huanghuaihai Plain

A field experiment was conducted in the Fengqiu State Key Agro-ecological Experimental Station in China's Henan Province to measure soil respiration in maize farmland ecosystems from June to October, 2010. Soil respiration was measured in the nine-treatment experiment using LI-COR-6400-09 Soil Respiration Chamber completed with Infrared Gas Analyzer (IRGA). The results indicated that soil respiration rates at 20 cm depth under treatments of burying straws in-between maize lines (ISFR) was significantly higher (P< 0.05) than those under the treatments of removing (NSFR) and mulching (SFR) straw with conventional fertilization. Average soil respiration rates of ISFR, NSFR and SFR were (209.22±75.63) mg(C)·m^-2·h^-1, (169.51±45.50) mg(C)·m^-2·h^-1 and (161.14±26.32) mg(C)·m^-2·h^-1, respectively. Average soil respiration rate under buried straw plus chemical N fertilizations of 16.8 kg(N)·hm^-2 (ISF1), 33.6 kg(N)·hm^-2 (ISF2) and 50.4 kg(N)·hm^-2 (ISF3) were (148.67±35.07) mg(C)·m^-2·h^-1, (124.11±23.18) mg(C)·m^-2·h^-1 and (178.85±46.60) mg(C)·m^-2·h^-1, respectively. The difference between ISF3 and ISF2 treatments was significant at ^P< 0.05. Under treatments of buried straw with chicken manure applications of 16.8 kg(N)·hm^-2 (ISOM1), 33.6 kg(N)·hm ^-2 (ISOM2) and 50.4 kg(N)·hm^-2 (ISOM3), average soil respiration rates were (135.07±21.97) mg(C)·m^-2·h^-1, (208.08±31.54) mg(C)·m^-2·h^-1 and (171.43±43.31) mg(C)·m^-2·h^-1, respectively. Compared with ISOM2, ISOM1 and ISOM3 significantly decreased soil respiration rates by 35.09% and 17.61%. The cumulative CO₂ emissions under ISOM1, ISOM2 and ISOM3 during maize growth were 324.16 g(C)·m^-2, 499.39 g(C)·m^-2 and 411.43 g(C)·m^-2, with significant differences in both cumulative CO₂ emissions and average soil respiration rates among the treatments at P < 0.05. Cumulative CO₂ emission under ISOM2 treatment during maize season was significantly higher than that under ISF2 treatment. It was therefore concluded that the effect of burying straws in-between maize lines combined with chicken manure on soil respiration rate was significantly greater than that with chemical N fertilizer. At chicken manure application rate of 33.6 kg(N)·hm ^-2, the conditions of C/N ratio were optimum for soil microbial metabolism and population.