Zhifeng CHEN ,Xiaohua DENG ,Miliang ZHOU,Feng TIAN,Mingfa ZHANG

1.China Tobacco Mid-south Agricultural Experimental Station,Changsha 410128,China;

2.Tobacco Monopoly Bureau of Xiangxi Autonomous Prefecture,Jishou 416000,China;

3.College of Agronomy,Hunan Agricultural University,Changsha 410128,China

Responsible editor:Nanling WANG Responsible proofreader:Xiaoyan WU

Xiangxi Autonomous Region has favorable ecological conditions,abundant light,heat and water resources,thus it is one of the important sound tobacco production areas in China[1-3].In recent years,flue-cured tobacco planting is mainly based on chemical fertilizer application,but lacks the mechanism of soil fertilizer,which causes soil hardening and the decline of organic matter and fertility,thereby affecting the quality of flue-cured tobacco.The planting of green manure in winter fallow farmlands for improving soil can not only make full use of light-heat resources,but also benefit the maintenance of ecologic equilibrium,thereby promoting the sustainable development of flue-cured tobacco production[4-6].There have been many studies on the mixed cropping technique of perennial forage and the forage of grassland-grass field rotation field[7-10],while the studies on the mixed cropping of annual green manure have been fewer[11-14],especially the studies on the mixed cropping of green manure in tobacco-planting soil.In this study,the effects of three kinds of monoculture and mixed cropping of green manure on physical and chemical properties of soil and economic characters of flue-cured tobacco were analyzed,so as to clear the suitable green manure cropping patterns in Xiangxi tobacco-planting areas,thereby providing a reference for the maintenance and improvement of tobaccoplanting soil in Xiangxi tobacco-growing areas.

Materials and Methods

Experimental design

The experiment was carried out in Qiangongping Township of Fenghuang County in Hunan Province during 2013-2014.Three kinds of green manure were selected to compare their monoculture and mixed cropping patterns,such as common vetch(Leguminosae sp.),perennial ryegrass(Gramineae) and rapeseed (Cruciferae).The experiment had 8 treatments:T1,common vetch monoculture; T2,perennial ryegrass monoculture; T3,cabbage-type rapeseed monoculture; T4,the mixed cropping between common vetch and perennial ryegrass; T5,the mixed cropping between common vetch and cabbagetype rapeseed;T6,the mixed cropping between cabbage-type rapeseed and perennial ryegrass; T7,the mixed cropping among common vetch,perennial ryegrass and cabbage-type rapeseed;CK,Blank(CK).There were 24 plots and the area of each was 33 m2,randomized block design with three repetitions was carried out.The green manure was sowed on October 20 of 2013,the seeding rates of common vetch,perennial ryegrass and cabbage-type rapeseed were 82.5,37.5 and 30 kg/hm2,respectively; the seeding rates of the mixed cropping of any two kinds of green manure were 50% of the corresponding monoculture,the seeding rates of the mixed cropping of the three kinds of green manure were 40%of the monoculture.The experimental variety of flue-cured tobacco was K326,which was transplanted on April 28 of 2014; the base fertilizer specialized for tobacco,specialized?topdressing,active fertilizer,hole applied fertilizer and potassium sulphate were 750,300,300,75 and 225 kg/hm2,respectively.The harvesting period of tobacco leaf was from July 20 to August 25 of 2014.Other management was performed according to Standardized Production Technology Solution of Xiangxi Flue-cured Tobacco.

Measuring items and methods

(1) The detection of physical and chemical properties of soil after green manure turnover.After the flue-cured tobacco pulling in the end of August,the samples of each treatment were got using cutting ring to measure soil bulk density.At the same time,five soil samples with 0-20 cm from the middle position of two tobaccoes were collected,then their soil nutrients were measured after mixing.For the measurement of soil pH,organic matter,total nitrogen (N),total phosphorus (P),total potassium (K),alkali-hydrolyzale N,rapidly available P and rapidly available K,normal analysis method was used.

(2) For the economic characters of flue-cured tobacco,the proportion of first-class tobacco,average price,yield and output were examined.

Statistical methods

Microsoft Excel 2003 and SPSS17.0 were adopted for data processing and statistical analysis.Duncan method was used for multiple comparisons,English small letters represented the differences reached significant level at 5%.

Results and Analyses

Effects of different mixed cropping patterns of green manure on soil bulk density

As shown in Table1,green manure turnover can reduce soil bulk density.After a growing season of fluecured tobacco,the falling range of soil bulk density was among 0.01-0.12 g/cm3,which decreased by 1.08% -8.62%compared with CK,the average falling rate was 4.39%.From different mixed cropping treatments of view,the decreasing amplitude of soil bulk density followed the sequence of T7＞T4＞T5 ＞T2 ＞T6 ＞T1 ＞T3.As a whole,the effect of the mixed cropping of the three kinds of green manure was the best,followed by the mixed cropping of any two kinds of green manure.

Effects of different mixed cropping patterns of green manure on soil pH

As seen in Table2,the influencerule of green manure turnover on soil pH was not obvious,the soil pH of T2,T3 and T4 treatments was lower than that of CK,while that of other treatments was higher than that of CK.

Effects of different mixed cropping patterns of green manure on soil organic matter

As shown in Table3,after green manure turnover,the increase range of soil organic matter was among 0.37-1.57 g/kg,which increased by 1.44%-6.10% compared with CK,the average increasing rate was 4.05%.The contents of soil organic matter under different mixed cropping patterns of green manure followed the sequence of T1＞T4＞T2＞T7＞T5＞T6＞T3＞CK;however,based on the results of variance analysis,the differences on the contents of soil organic matter under different treatments were not significant.

Table2 Effects of different mixed cropping patterns of green manure on soil pH

Table3 Effects of different mixed cropping patterns of green manure on soil organic matter

Effects of different mixed cropping patterns of green manure on soil soil N contents

As seen in Table4,after green manure turnover,the increase range of soil alkali-hydrolyzale N contents was among 1.54-17.02 mg/kg,which increased by 1.06% -11.76% compared with CK,the average increasing rate was 7.07%.The contents of soil alkali-hydrolyzale N under different mixed cropping patterns of green manure followed the sequence of T1＞T7＞T4＞T2＞T5＞T6＞T3＞CK; according to the results of variance analysis,the contents of soil alkali-hydrolyzale N under different treatments were significantly higher than that of CK (except treatment T3),and the contents of soil alkali-hydrolyzale N under the patterns of common vetch monoculture,the mixed cropping between common vetch and perennial ryegrass and the mixed cropping among common vetch,perennial ryegrass and cabbage-type rapeseed were higher.

After green manure turnover,the increase range of soil total N contents was among 0.01-0.12 g/kg,which increased by 0.59%-7.06% compared with CK,the average increasing rate was 3.03%.The contents of soil total N under different mixed cropping patterns of green manure followed the sequence of T1＞T7＞T2＞T5＞T6＞T4＞T3＞CK; the results of variance analysis showed that there were not obvious differences on the contents of soil total N under different treatments.

Effects of different mixed cropping patterns of green manure on soil P contents

As shown in Table5,after green manure turnover,the increase range of soil available P contents was among 0.02-10.20 mg/kg,which increased by 0.04% -18.93% compared with CK,the average increasing rate was 6.24%.The contents of soil available P under different mixed cropping patterns of green manure followed the sequence of T1＞T7＞T4＞T5＞T6＞T2＞T3＞CK;the results of variance analysis showed that there were not obvious differences on the contents of soil available P under different treatments.

After green manure turnover,the increase range of soil total P contents was among 0.01-0.06 g/kg,which increased by 1.89%-11.32% compared with CK,the average increasing rate was 7.82%.The contents of soil total P under different mixed cropping patterns of green manure followed thesequence of T1＞T2＞T4＞T7＞T6＞T5＞T3＞CK;the results of variance analysis showed that there were not obvious differences on the contents of soil total P under different treatments.

Table4 Effects of different mixed cropping patterns of green manure on soil soil N contents

Table5 Effects of different mixed cropping patterns of green manure on soil P contents

Table6 Effects of different mixed cropping patterns of green manure on soil K contents

Table7 Effects of different mixed cropping patterns of green manure on economic characters of flue-cured tobacco

Effects of different mixed cropping patterns of green manure on soil K contents

As seen in Table6,after green manure turnover,the increase range of soil rapidly available K contents was among 2.00-47.00 mg/kg,which increased by 0.98%-23.12% compared with CK,the average increasing rate was 8.60%.The contents of soil rapidly available K under different mixed cropping patterns of green manure followed the sequence of T4 ＞T1 ＞T2 ＞T7＞T6＞T3＞T5＞CK;the results of variance analysis showed that there were not obvious differences on the contents of soil rapidly available K under different treatments.

After green manure turnover,the increase range of soil total K contents was among 0.03-0.90 g/kg,which increased by 0.12%-3.56% compared with CK,the average increasing rate was 2.61%.The contents of soil total K under different mixed cropping patterns of green manure followed the sequence of T1＞T4＞T5＞T7＞T2＞T6＞T3＞CK; the results of variance analysis showed that there were not obvious differences on the contents of soil total K under different treatments.

Effects of different mixed cropping patterns of green manure on economic characters of flue-cured tobacco

As shown in Table7,different mixed cropping patterns of green manure had not obvious effects on the proportion of first-class tobacco and average price,but after green manure turnover,the yield and output of fluecured tobacco were higher that those of CK.From the yield and output of flue-cured tobacco,the yield and output of flue-cured tobacco under the patterns of common vetch monoculture,perennial ryegrass monoculture,the mixed cropping between common vetch and perennial ryegrass and the mixed cropping among common vetch,perennial ryegrass and cabbage-type rapeseed were relatively higher,but the yield and output of flue-cured tobacco under the pattern of common vetch monoculture were the highest.

Conclusions and Discussions

Green manure turnover can reduce soil bulk density by 1.08% -8.62%,moreover,the effect of soil bulk density decrease by the mixed cropping of green manure was the best.

Green manure turnover also can increase soil nutrient,the average values of the relative increment of soil organic matter,available N,available P,rapidly available K,total N,total P and total K under the 7 treatments were 10.64%,5.45%,1.13%,8.50%,3.21%,3.41%and 7.05%,respectively,moreover,the effect of soil nutrient increase under common vetch monoculture was the best,follwed by the mixed cropping between common vetch and perennial ryegrass,the third was the mixed cropping of the three kinds of green manure,the effect of cabbage-type rapeseed monoculture was the worst.There was not chemical fertilizer application in the green manure planting,and the emergence rates of perennial ryegrass and rapeseed were not high,thereby the biomass of perennial ryegrass and rapeseed was lower than that of common vetch.From the biomass of green manure of view,the biomass of common vetch monoculture was the highest,thus the effect of common vetch monoculture on soil nutrient increase was the best.

Under different treatments of green manure turnover,the differences on the proportion of first-class tobacco and average price were not significant,but green manure turnover can improve the yield and output of flue-cured tobacco,in which the effect of common vetch monoculture was the best.

In general,the effects of soil improvement,and the yield and output improvement of flue-cured tobacco under the four mixed cropping patterns were lower than those of common vetch monoculture.Therefore,in the extensive cultivation of green manure in the dry land of Xiangxi tobaccoplanting areas,the monoculture of common vetch should be generalized.

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