不同施氮量对半干旱区还田玉米秸秆腐解及养分释放特征的影响

为了揭示还田玉米秸秆在不同施氮水平下的腐解及养分释放特征,在马铃薯田间定位试验中,设置了6个不同施氮水平(T1:0 kg·hm~(-2);T2:75 kg·hm~(-2);T3:150 kg·hm~(-2);T4:225 kg·hm~(-2);T5:300 kg·hm~(-2); T6:375 kg·hm~(-2)),研究其对还田玉米秸秆腐解及养分释放特征的影响。研究表明:还田玉米秸秆的腐解主要发生在前90 d,在此期间玉米秸秆腐解较快,T1～T6处理的玉米秸秆腐解率分别为37.3%、40.3%、44.8%、45.0%、50.8%、48.4%,以T5处理为最高,处理间差异显著(P0.05);同时,T1～T6处理的玉米秸秆碳、氮释放率分别为48.2%～56.6%、33.8%～44.4%,T5处理下秸秆的碳、氮释放率均显著高于其他处理(P0.05),而秸秆磷、钾的释放率分别为43.1%～49.2%、90.5%～93.0%,处理间无显著性差异。还田150 d后,玉米秸秆的腐解率为52.7%～55.8%,养分释放表现为KCPN。综上所述,连续施氮可以显著促进还田玉米秸秆前期的腐解及碳氮的释放,但对磷钾的释放无明显影响,当施氮量为300 kg·hm~(-2)时还田玉米秸秆的腐解效果最好。

Effects of application of different nitrogen levels on decomposition characteristics and nutrient release of returning straw

In order to determine the decomposition dynamics and nutrient release of maize straw return under different nitrogen (N) application rates, a field experiment was conducted at Dingxi County in the Gansu Province of China.The experiment had six N treatments including no-N application (0 kg·hm^-2, T1), 75 kg·hm^-2 (T2), 150 kg·hm^-2 (T3), 225 kg·hm^-2 (T4), 300 kg·hm^-2 (T5), and 375 kg·hm^-2 (T6) with four replications. The 42.6 g of maize straw was incorporated into each of the treatments by nylon mesh bag method. Results from the experiment revealed that maize straw decomposition occurred within the first 90 days after returning into the soil and the decomposition rate increased rapidly during this period.The decomposition rate of corn straw was 37.3%, 40.3%, 44.8%, 45.0%, 50.8%, and 48.4% in T1~T6 treatments, respectively. Treatment T5 significantly (P<0.05) achieved the highest decomposition rate throughout the decomposition period. At the same time, the release rates of C and N of maize straw in T1~T6 treatments were 48.2%~56.6% and 33.8%~44.4%, respectively. The release rates of C and N of maize straw in T5 treatment were significantly higher than those in other treatments (P<0.05).However, the release rates of P and K were 43.1%~49.2% and 90.5%~93.0%, there was no significant difference among all the treatment (P>0.05). The rate of straw decomposition after 150 days ranged from 52.7% to 55.8%, and the nutrient release was ranked as K>C>P>N. In summary, the continuous application of different nitrogen rates significantly influenced straw decomposition rate and the release of carbon and nitrogen, however the release rates of phosphorus and potassium were not statistically significant. The T5 (300 kg·hm^-2) had the greatest impact on decomposition.