Effects of Crop Stubble on Physicochemical Properties of Continuous Cropping Soil and Cucumber Yield and Quality

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1 Nturl Resources, 2012, 3, Published Online September 2012 ( Effects of Crop Stubble on Physicochemicl Properties of Continuous Cropping Soil nd Cucumber Yield nd Qulity Yuyn Wng 1,2, Zhongwei Wng 1*, Guichun Yng 1, Li Wng 1, Yi Zheng 1 1 Institute of Economic Botny, Jilin Acdemy of Agriculturl Sciences, Gongzhuling, Chin; 2 Eco-Agriculture Reserch Center, Binzhou Voctionl College, Binzhou, Chin. Emil: * @163.com Received My 29 th, 2012; revised August 3 rd, 2012; ccepted August 14 th, 2012 ABSTRACT By pot experiment, two kinds of crop stubble (whet, soyben) were dded into continuous cropping soil of cucumber ccording to different quntity (0.5%, 1% nd 2%), the effects of different kinds of stubble nd quntity on the continuous cropping soil nd growth of cucumber were investigted. The results showed tht two kinds of crop stubble significntly decresed soil bulk density, nd incresed totl porosity of soil. Ech of ll tretments significntly decresed the ccumultion of slinity in soil within the entire growth period of cucumber. 2% whet stubble tretment hd the biggest drop in soil EC in the lter period of cucumber growth. Soyben stubble tretment hd the lesser effect on soil EC. Whet nd soyben stubble promoted the growth of cucumber, incresed the yield of cucumber, nd improved the qulity of cucumber. 2% of whet stubble tretment hd biggest increse in cucumber yield, which incresed the yield by 34.23% compred with the control. Keywords: Whet; Soyben; Stubble; Continuous Cropping Cucumber; Sick Soil; Yield nd Qulity; Physicochemicl Properties 1. Introduction Along with the continuous development of protected vegetbles, it is incresingly common tht the sme kind of vegetble ws continuously grown in the sme piece of lnd, so, the soil diseses in protected vegetbles cultivtion becomes more nd more severe [1]. A number of vegetbles in protected cultivtion such s cucumber, tomto, eggplnts, pepper nd so on hve frequently suffered continuous cropping obstcles, the continuous cropping obstcle often cused these plnts wek growth, inferior fruit qulity nd specil soil diseses [2,3]. The cucumber is one of the min types to be cultivted in protected vegetbles, nd it is even extremely intolernt to continuous cropping. Therefore, the continuous cropping obstcles of cucumber is more severe, which hs lredy become one of the mjor fctors for restricting the yield nd qulity of protected cucumber. Thus, it is imminent to solve the problem of continuous cropping obstcle of protected cucumber. In order to explore the effective wys nd mesures to overcome or reduce continuous cropping obstcle of pro- * Corresponding uthor. tected vegetbles, griculturl experts hd contributed lot of reserch work. Currently there re three kinds of remedition technologies including physicl, chemicl nd bioremedition to continuous cropping soils [4]. However, these technologies ll hve certin limittions. Some studies showed tht orgnic mterils could improve the physicochemicl properties of continuous cropping soil, increse the diversity of microbil community structure in soil, inhibit the reproduction of pthogenic microorgnisms in soil, nd reduce the ccumultion of toxic substnces in soil [5]. For exmple, strw returning hd very good effects for improving nd cultivting the sick soil [6], the ppliction of strw mixed with biopreprte could improve the continuous cropping soils in greenhouse, even could promote the growth nd development of vegetble [7]. In order to discover more effective wys nd mesures for overcoming or reducing continuous cropping obstcle of protected vegetbles, we plced two kinds of crushed crop stubble (whet nd soyben) into the soil of continuous cropping cucumber for study. Currently, the studies of effect of whet, soyben stubble on the continuous cropping obstcle of cucumber hve not been reported. At the sme time, the strw nd stubble re wste in frmlnd, if which re

2 Effects of Crop Stubble on Physicochemicl Properties of Continuous Cropping Soil nd Cucumber Yield nd Qulity 89 used for improving the continuous cropping soil, the resources will be sved, nd environmentl pollution will be reduced. Therefore, this study hs gret pplicted vlue nd theoreticl significnce. In ddition, becuse the llelopthy is ubiquitous in crops, nd it hs significnt effect on seed germintion nd crop growth [8], so the types of stubble to be used for improving continuous cropping soil of cucumber should be strictly selected. Menwhile, the consumption of stubble dding, the methods of stubble dding nd other issues ll need to be further studied. To this end, in this study, we selected two kinds of crops stubble (whet nd soyben) nd plced them into continuous cropping soils of cucumber in greenhouse to study the effect of the crops stubble on the continuous cropping soils nd cucumber growth, so tht we cn provide scientific bsis nd technicl methods for solving the problem of continuous cropping obstcles in protected vegetbles. 2. Mterils nd Methods 2.1. Experimentl Mterils Whet (Triticum eslivum L.) vriety: Kefeng No. 6, soyben (Glycine mx) vriety: North 86-4, cucumber (Cucumis stivus L.) vriety: Tinjin Green No. 3. The tested stubble: Whet nd soyben stubble were obtined from the residues of previous crops hrvested, including the roots. When the crops stubble ws collected, firstly, the stubble ws dug from soil, nd then clened, dried, nd crushed by the grinder [8]. The physicochemi- cl properties of the crops stubble were s shown in the following tble (Tble 1). The tested soil: the smpled soil ws tken from continuous cropping soil of cucumber in greenhouse, the bsic physicochemicl properties of the smpled soil prior the experiment were s shown in the following tble (Tble 2) Pot Study Here, studies were done in pots in Mrch to August, The dimeter of pot ws 30 cm, 22 cm high, loding 8 kg of soil per pot. First, the soil of continuous cropping cucumber ws sieved through 6 mm sieve to remove lrger clods nd the other plnt residues etc. Second, the sieved soils nd crushed stubble were uniformly mixed together ccording to the different weight rtio (Tble 3). Third, we plced the mixed soils into pots (8 kg per cm pot). Then, these pots were dequtely wtered, covered by plstic film to decompose for 21 dys in solr greenhouse. To relese some of hrmful gses, the plstic film hd been removed for week when cucumber seedlings were plnted. The pots were plced on ground in solr greenhouse s cm, nd 5 g dimmonium phosphte ws put into per pot, cucumber seedlings were plnted fter three dys. The pots without stubble were used s the controls (CK). The experiment included totl of 7 tretments (2 kinds of stubble 3 kinds of dosge + 1 control). And these tretments were repeted 3 times, we used 30 pots for ech tretment, mking totl of 630 pots. Tble 1. Physicochemicl properties of the tested stubble. Tested stubble crbon (mg g 1 ) nitrogen (mg g 1 ) phosphorus (mg g 1 ) potssium (mg g 1 ) C/N Whet Soyben Tble 2. Physicochemicl properties of the tested soils. nitrogen Alklihydrolysible N (mg kg 1 ) hosphorus Quick cting P potssium Quick cting K Orgnic mtte (%) ph EC (ms cm 1 ) Tble 3. The Symbols used for different stubble nd quntity. Stubble Whet Soyben Control Adding quntity 0.5% 1% 2% 0.5% 1% 2% 0 Symbol A1 A2 A3 B1 B2 B3 CK

3 90 Effects of Crop Stubble on Physicochemicl Properties of Continuous Cropping Soil nd Cucumber Yield nd Qulity 2.3. Smpling nd Determintion Smpling: We smpled one time per 20 dys fter the cucumber seedlings plnting, mking totl of 3 times. We rndomly selected 3 pots to collect rhizosphere soil ech time, the topsoil in the vicinity of the cucumber plnts ws removed before collecting rhizosphere soil. The soil smples of 3 replictions were collected respectively, then mixed, sieved through 2 mm sieve. The soil smples were ir-dried for storge, which were used for determining physicochemicl indictors of the continuous cropping soil nd soil enzyme ctivity. Soil indictors: Soil ph ws determined using the PHS-2F digitl ph meter, Soil EC by using DDS-11A conductivity, the soil bulk density by using cutting ring, totl porosity of soil ws clculted by soil bulk density (r) nd soil proportion (d), the formul is s follows: p1 1 r d 100%. The soil density ws replced by the men vlue of generl soil, tking 2.65 (g/cm 3 ). The soil moisture ws determined using drying weight method, the formul is s follows: Soil moisture (%) = W W W W % 9,10. Cucumber yield: Five plnts were chosen rbitrrily in ech tretment, nd were mrked. We recorded yield of ech plnt singly, took their verge, nd then converted it into the yield of per hectre (hm 2 ). Cucumber qulity: Soluble solids were determined using hnd-held sugr meter (Mde in Jpn), Vc content by using 2,6-dichlorophenol indophenol titrtion. Tste ws evluted by using sensory identifiction method. 3. Results 3.1. Physicochemicl Properties of Soil Bulk Density nd Porosity Whet nd soyben stubble decresed the bulk density of soil, nd incresed soil porosity (Tble 4). All whet stubble tretments decresed significntly bulk density of soil, moreover, the bulk density constntly decresed s the increse of whet stubble quntity. A2 nd A3 hd the lrger reduction, but there ws no significnt difference between the A2 nd A3. Soyben stubble hd lso similr effect, but the effect of soyben stubble ws smller thn tht of whet stubble. This shows tht two kinds of crop stubble help to decrese bulk density of soil, nd increse the soil permebility. However, ech of stubble tretments hd contrry result on the porosity of soil. All tretments incresed the porosity of soil, moreover, the porosity constntly incresed s the increse of stubble quntity. 2% whet stubble hd gretest effect on the porosity of soil, incresing by 24.4% thn the control, nd followed by 2% soyben stubble, incresing by 18.96% Soil Moisture Two kinds of crop stubble hd certin effect on soil ph, but the effect ws different in different growth periods (Figure 1). In the pre-stge of cucumber growth, two kinds of stubble incresed the moisture of soil, whet stubble hd greter effect on the moisture of soil compred with soyben stubble. The gretest effect ws observed in 2% whet stubble tretment, which incresed the moisture by 26.37% compred with control. Soyben stubble tretments hd similr effects, but these effects were smller, in prticulr, 0.5% soyben stubble hd minimum effect, which hd no difference compred with the control. In the medium term, whet stubble tretment incresed lrgely the moisture of soil, 2% of whet stubble hd gretest ffect on the moisture, which ws significntly higher thn other tretments nd control, incresed by 34.35% thn control. Soyben stubble tretment hd lso similr effects, 2% of soyben stubble tretment hd gretest ffect on the moisture. In the lter period, ll tretments incresed the soil moisture too, but these tretments hd lesser increse in soil moisture. Tble 4. Effect of different tretments on bulk density nd porosity of soil. Tretments Bulk density (g cm 3 ) porosity (%) A ± 0.08bc ± 6.16c A ± 0.08d ± 8.02b A ± 0.06d ± 6.33 B ± 0.05b ± 4.61cd B ± 0.07c ± 7.12bc B ± 0.03c ± 3.13b CK 1.41 ± ± 5.18e Note: Vlues re mens ± stndrd devition. Significnt differences (P < 0.05 using Duncn s multiple rnge test) mong tretments in the sme column re indicted by different letters, the sme s below.

4 Effects of Crop Stubble on Physicochemicl Properties of Continuous Cropping Soil nd Cucumber Yield nd Qulity 91 Soil moisture( % ) b e d b d b bc d c e f e c c b e e cd Dys fter plnting A1 A2 A3 B1 B2 B3 CK Figure 1. Effect of different tretments on moisture of soil Soil ph Two kinds of stubble hd certin effect on soil ph, but the effect ws reltively smller (Tble 5). In the prestge nd mid of growth, most of the stubble tretments decresed soil ph, only the 2% whet stubble (A3) incresed it. 2% whet stubble tretment hd the gretest increse in the soil ph, but there ws significnt difference between it nd control. Other tretments hd no significnt difference too. In the lter stge of growth, ll stubble tretments decresed soil ph but only 2% whet stubble tretment incresed it. 2% whet stubble tretment ws significntly higher thn control, while other tretments hd on significnt difference compred with control. The mximum decrese ws observed in the 1% soyben stubble tretment, but it hd on significnt difference compred with control Soil EC Two kinds of stubble hd reltively lrger effect on soil EC (Tble 6). In the pre-stge of cucumber growth, ll whet stubble tretments significntly decresed soil EC, mximum decrese ws observed in 1% whet stubble tretment, nd followed by 0.5% whet stubble tretment. Soyben stubble lso decresed soil EC, the soil EC vlues of ll soyben stubble tretments were significntly lower thn the control, 0.5% nd 1% of soyben stubble hd greter decrese in soil EC. In the mid-nd lte, whether whet stubble or soyben stubble ll showed the similr lws in soil EC Cucumber Yield Two kinds of stubble incresed yield of cucumber (Figure 2). All tretments of whet stubble mrkedly incresed yield of cucumber, the highest yield ws observed in 2% whet stubble tretment, which incresed the yield by 34.23% compred with control. Soyben stubble incresed yield of cucumber too, but soyben stubble tretment hd the smller increse thn whet stubble tretment. The higher yield ws observed in 1% soyben stubble tretment, which incresed the yield by 16.01% compred with control. Tble 5. Effect of different tretments on soil ph fter plnting. Tretments 20 dys 40 dys 60 dys A ± 0.04b 7.35 ± 0.08b 7.33 ± 0.16bc A ± 0.14b 7.47 ± 0.17b 7.27 ± 0.14bc A ± ± ± 0.05 B ± ± 0.03b 7.34 ± 0.05bc B ± 0.12b 7.35 ± 0.05b 7.26 ± 0.03bc B ± 0.09b 7.30 ± 0.06b 7.28 ± 0.08bc CK 7.61 ± ± ± 0.11b Tble 6. Effect of different tretments on soil EC fter plnting (ms/cm). Tretments 20 dys 40 dys 60 dys Yield Yield(kg. (kg hm hm-2) -2 ) A ± 0.04f 1.07 ± 0.06e 0.82 ± 0.03f A ± 0.07cd 1.04 ± 0.07e 0.88 ± 0.06ef A ± 0.02e 1.01 ± 0.04e 0.80 ± 0.06f B ± 0.09c 1.13 ± 0.06d 0.93 ± 0.08e B ± 0.07c 1.16 ± 0.05d 1.38 ± 0.03b B ± 0.08b 1.37 ± 0.09c 1.25 ± 0.04c CK 1.62 ± ± ± A1 e A2 b A3 B1 de B2 tretments Figure 2. Effect of different tretments on the yield of cucumber. c B3 f CK fg

5 92 Effects of Crop Stubble on Physicochemicl Properties of Continuous Cropping Soil nd Cucumber Yield nd Qulity 3.3. Cucumber Qulity As cn be seen from Tble 7, whet stubble significntly improved cucumber qulity. First, whet stubble incresed the content of dry mtter, moreover, the content of dry mtter grdully incresed s the increse of whet stubble quntity. Second, whet stubble incresed the content of vitmin C nd soluble solids in fruits, but 0.5% whet stubble tretment hd no difference compred with the control. Third, whet stubble decresed the incidence of deformed fruits. The gretest decrese ws observed in 2% whet stubble tretment, nd followed by 1% whet stubble tretment. Soyben stubble hd certin effect in improving fruit qulity too. 0.5% nd 1% of soyben stubble tretments incresed the content of dry mtter, while n opposite result ws observed in 2% of tretment. Soyben stubble hd no obvious regulrity on the content of vitmin C nd soluble solids in fruits, which ws sometimes scending nd sometimes descending. 0.5% of soyben stubble tretment significntly incresed the content of vitmin C in fruits, but it hd little effect on the soluble solids. 2% of soyben stubble tretment decresed the incidence of deformed fruits, which ws significntly lower thn control. 4. Conclusions Mny studies showed tht orgnic mterils decresed soil bulk density, incresed totl porosity, incresed soil ggregte structure, nd improved soil permebility when they were dded into soil [9,10]. At the sme time, orgnic mterils could increse soil ph, nd lower soil EC, even tht they could improve the physicochemicl properties [11,12]. In this test, whether whet stubble or soyben stubble obviously decresed soil EC, especilly in the lter period, the decrese of soil EC ws greter. Ech of ll tretments significntly decresed the slinity ccumultion in soil within the entire growth period of cucumber, mximum decrese of the EC ws observed in 2% whet stubble tretment, while effect of two kinds of stubble on soil ph ws not obvious. This my be relted to the microbil metbolism, becuse the stubble cn provide more nutrients for the microorgnisms in soil, nd promote the ctivity of microorgnisms. Thus, whet or soyben stubble cn reduce continuous cropping obstcle in greenhouse soil. For exmple, when two kinds of stubble re dded into the continuous cropping soil, mny of the problems such s soil compction, stliniztion, poor permebility nd poor wter holding cpcity, even some soil sickness will be solved. Therefore, whet stubble or soyben stubble hs positive effect in promoting cucumber growth nd improving sick soil. Soil moisture is n importnt indictor relted to soil microorgnism ctivity nd crop growth, which directly ffects the growth nd yied of crops. According to reserch report [13,14], strw returning enhnced the bilities for soil to retin wter nd nutrients, increse cpcity of holding wter, nd improve the effectiveness of nturl precipittion. Wng [15] (2000) studied the effects of strw for different processing methods on soil moisture, the results showed tht strw returning improved soil moisture conditions, incresed the cpcity of wter storge nd wter retention in soil. In this test, the results showed tht two kinds of stubble incresed soil moisture, while the effect of whet stubble on soil moisture ws greter thn tht of soyben stubble, nd 2% of whet stubble hd gretest effect, which incresed soil moisture by 26.37% compred with control. One of the min resons is tht the density of whet stubble is smller thn tht of soyben stubble, so the volume of whet stubble is reltively lrger thn tht of soyben stubble. Therefore, whet stubble tretment hs greter increse on soil totl porosity thn soyben stubble, so whet stubble is more conducive to increse the soil moisture. In ddition, becuse the density of Tble 7. Effect of different tretments on the qulity of cucumber. Tretment Deformed fruits rte (%) Dry mtter (%) Vitmin C (mg/100g FW) Soluble solids (%) Tste A ± 0.13c 3.15 ± 0.08cd 9.85 ± 0.09e 7.6 ± 0.06d Good A ± 0.08e 3.84 ± 0.06b ± 0.13b 9.1 ± 0.09 Excellent A ± 0.06ef 3.96 ± 0.11b ± ± 0.06b Excellent B ± 0.16c 3.33 ± 0.10c ± 0.18b 8.1 ± 0.12b Good B ± 0.06d 3.37 ± 0.04c ± 0.12d 7.9 ± 0.07b Excellent B ± ± 0.06ef ± 0.11d 7.5 ± 0.10d Good CK 9.67 ± 0.11c 2.63 ± 0.07e 9.66 ± 0.07e 7.8 ± 0.11d Generl

6 Effects of Crop Stubble on Physicochemicl Properties of Continuous Cropping Soil nd Cucumber Yield nd Qulity 93 whet stubble is smller thn tht of soyben stubble, so more whet stubble ws floted on the wter when wtering, nd it ws just ttched to the soil surfce fter the wter seeping down, thus whet stubble tretment cn decrese wter evportion, nd reltively increse the soil moisture. This my be nother reson tht the whet stubble is more conducive to increse the soil moisture. According to studies, there re three mjor resons on continuous cropping obstcle of cucumber: First, the nutrients in soil were in imblnce, the physicochemicl properties of soil becme worse. Second, the pthogens in soil proliferted quickly, the ecologicl environments of microorgnisms were destroyed, nd the biologicl properties of soil becme worse. Third, it is due to the llelopthy of the root exudtes nd the stubble decomposition [5,16,17]. It is exctly effective wys nd mesures for Mixed intercropping, crop rottion nd the development nd ppliction of soil remedition gents to solve this problem. According to the investigtion, strw return cn promote the growth of crops, increse crop yields by 5% - 10% [18,19]. According to nother report, orgnic mteril lso cn increse cucumber yields when it ws dded into soil in the greenhouse [4,20]. In our experiment, whet nd soyben stubble promoted the growth of cucumber, incresed yield of cucumber. Among, 1% nd 2% of whet stubble mrkedly incresed yield of cucumber, the highest increse of yield ws observed in 2% whet stubble tretment, which incresed the yield by 34.23% compred with control. Thus, two kinds of crop stubble cn coordinte the wter, gs, het, nutrient nd other conditions in soil, improve the physicochemicl properties of soil. So, this helps to estblish good foundtion for cucumber growth nd yield increse. 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