黔西北喀斯特区坡耕地有机覆盖措施保墒效应

Effects of organic mulching measures on soil moisture conservation of sloping farmland in karst areas of northwest Guizhou

基于喀斯特地区工程性缺水问题,探讨喀斯特区坡耕地有机覆盖措施对土壤水分的影响,对提高区域自然降水利用效率、增加作物产量具有重要意义。以传统玉米单作(CK)为对照,针对秸秆覆盖(SM)、生物炭覆盖(BM)和粮草间作(GI)等有机覆盖,依据覆盖量不同分别设5个秸秆覆盖处理(SM1~SM5)、4个生物炭覆盖处理(BM1~BM4),同时依据间作植物的不同分别设玉米间作紫花苜蓿(AI)、菊苣(CI)和黑麦草(RI)3个粮草间作处理,共计13个处理,历时1个植物生长季,对坡耕地耕作层土壤水分动态进行野外定位观测,2018年全年共观测记录46次。结果表明:1)随着秸秆覆盖量的增加,耕作层土壤水分呈上升趋势,当秸秆覆盖量达SM5时,水分含量达最大值,显著高于CK及SM1~SM3(P<0.05),但较SM4无显著差异,即当秸秆覆盖量由5556 kg/hm^2(SM4)增加至6944 kg/hm^2(SM5)时,水分含量未再显著增加;2)随着生物炭覆盖量的增加,水分含量呈增加趋势,但与CK相比,各覆盖量处理均未显著提高水分含量(P>0.05);3)AI水分含量要高于CK、CI和RI,但并未达显著性水平(P>0.05);4)秸秆覆盖整体保墒效果要优于生物炭覆盖及粮草间作,但并未达显著水平(P>0.05)。综上,6000 kg/hm^2左右的秸秆覆盖率可起到较好的保墒效果,可能是西南喀斯特区较为适宜的参考覆盖量。生物炭及粮草间作覆盖整体保墒效果不明显,但生物炭覆盖可能是物候关键期或者干旱期一种适宜的保墒覆盖措施。

[Background]Considering the problem of“engineering”water shortage in karst areas,understanding the effects of organic mulch on soil moisture of sloping farmland in karst areas is of great significance to improve the utilization efficiency of regional natural precipitation and to increase crop yield.[Methods]The maize monoculture was set as control(CK),5 straw mulch treatments(SM1 by straw 1111 kg/hm^2,SM2 by straw 2222 kg/hm^2,SM3 by straw 3889 kg/hm^2,SM4 by straw 5556 kg/hm^2,and SM5 by straw 6944 kg/hm^2)and 4 biochar mulch treatments(BM1 by biochar 1389 kg/hm^2,BM2 by biochar 2778 kg/hm^2,BM3 by biochar 5556 kg/hm^2,and BM4 by biochar 11111 kg/hm^2)were set,and alfalfa(AI),chicory(CI)and ryegrass intercropping(RI)in maize were set as 3 grain and grass intercropping treatments according to the difference of intercropping plants,13 treatments in total.During the whole growing season,the soil moisture dynamics in the cultivated layer was observed in the field and 46 observations were recorded in the whole year of 2018.[Results]1)With the increase of straw mulch application rate,the soil moisture in tillage layer showed an upward trend.When the straw mulch application rate was up to SM5,the soil moisture reached the maximum,which was significantly higher than CK and SM1-SM3(P<0.05),but not significantly higher than SM4,that was,when the straw mulch application rate increased from 5556(SM4)to 6944 kg/hm^2(SM5),the soil moisture did not increase significantly.2)With the increase of biochar mulch application rate,the soil moisture also showed an increasing trend,but did not reach a significant level(P>0.05).3)Soil moisture under AI was higher than that of CK,CI and RI,but did not reach the significant level(P>0.05).4)Among the three different organic mulches,the overall effect of SM on soil moisture conservation was better than that of BM and GI,but did not reach the significant level(P>0.05).[Conclusions]The straw mulch of about 6000 kg/hm^2presents promising effect on soil moisture conservation,and might be an appropriate reference mulch application rate for karst areas in Southwest China.The effect of biochar mulch and grain and grass intercropping on soil moisture conservation is not significant,however,biochar mulch might be a suitable organic mulch to conserve soil moisture during critical phenological or drought periods.