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

doi:10.4236/nr.2012.33013

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Natural Resources, 2012, 3, 88-94

http://dx.doi.org/10.4236/nr.2012.33013 Published Online September 2012 (http://www.SciRP.org/journal/nr)

Effects of Crop Stubble on Physicochemical Properties of

Continuous Cropping Soil and Cucumber Yield and

Quality

Yuyan Wang1,2, Zhongwei Wang1*, Guichun Yang1, Li Wang1, Yi Zheng1

1Institute of Economic Botany, Jilin Academy of Agricultural Sciences, Gongzhuling, China; 2Eco-Agriculture Research Center,

Binzhou Vocational College, Binzhou, China.

Email: *[email protected]

Received May 29th, 2012; revised August 3rd, 2012; accepted August 14th, 2012

ABSTRACT

By a pot experiment, two kinds of crop stubble (wheat, soybean) were added into continuous cropping soil of cucumber

according to different quantity (0.5%, 1% and 2%), the effects of different kinds of stubble and quantity on the con-

tinuous cropping soil and growth of cucumber were investigated. The results showed that two kinds of crop stubble sig-

nificantly decreased soil bulk density, and increased total porosity of soil. Each of all treatments significantly decreased

the accumulation of salinity in soil within the entire growth period of cucumber. 2% wheat stubble treatment had the

biggest drop in soil EC in th e later period of cucumber growth. Soybean stubble treatment had the lesser effect on soil

EC. Wheat and soybean stubble promoted the growth of cucumber, increas ed the yield of cucu mber, and improv ed the

quality of cucumber. 2% of wheat stubble treatment had a bigg est increase in cucu mber yield , which increased th e yield

by 34.23% compared with the control.

Keywords: Wheat; Soybean; Stubble; Con tinuou s Cropping Cucumber; Sick Soil; Yield and Quality; Physicochemical

Properties

1. Introduction

Along with the continuous development of protected

vegetables, it is increasingly common that the same kind

of vegetable was continuously grown in the same piece

of land, so, the soil diseases in protected vegetables cul-

tivation becomes more and more severe [1]. A number of

vegetables in protected cultivation such as cucumber,

tomato, eggplants, pepper and so on have frequently suf-

fered continuous cropping obstacles, the continuous crop-

ping obstacle often caused these plants weak growth, in-

ferior fruit quality and special soil diseases [2,3]. The

cucumber is one of the main types to be cultivated in

protected vegetables, and it is even extremely intolerant

to continuous cropping. Therefore, the continuous crop-

ping obstacles of cucumber is more severe, which has

already become one of the major factors for restricting

the yield and quality of protected cucumber. Thus, it is

imminent to solve the problem of continuous cropping

obstacle of protected cucumber.

In order to explore the effective ways and measures to

overcome or reduce continuous cropping obstacle of pro-

tected vegetables, agricultural experts had contributed a

lot of research work. Currently there are three kinds of

remediation technologies including physical, chemical

and bioremediation to continuous cropping soils [4]. How-

ever, these technologies all have certain limitations.

Some studies showed that organic materials could im-

prove the physicochemical properties of continuous crop-

ping soil, increase the diversity of microbial community

structure in soil, inhibit the reproduction of pathogenic

microorganisms in soil, and reduce the accumulation of

toxic substances in soil [5]. For example, straw returning

had very good effects for improving and cultivating the

sick soil [6], the application of straw mixed with bio-

preparate could improve the continuous cropping soils in

greenhouse, even could promote the growth and devel-

opment of vegetable [7]. In order to discover more ef-

fective ways and measures for overcoming or reducing

continuous cropping obstacle of protected vegetables, we

placed two kinds of crushed crop stubble (wheat and

soybean) into the soil of continuous cropping cucumber

for study. Currently, the studies of effect of wheat, soy-

bean stubble on the continuous cropping obstacle of cu-

cumber have not been reported. At the same time, the

straw and stubble are waste in farmland, if which are

*Corresponding a uthor.

Effects of Crop Stubble on Physicochemical Properties of Continuous Cropping Soil and Cucumber Yield and Quality 89

used for improving the continuous cropping soil, the re-

sources will be saved, and environmental pollution will

be reduced. Therefore, this study has great applicated

value and theoretical significance.

In addition, because the allelopathy is ubiquitous in

crops, and it has significant effect on seed germination

and crop growth [8], so the types of stubble to be used

for improving continuous cropping soil of cucumber

should be strictly selected. Meanwhile, the consumption

of stubble adding, the methods of stubble adding and

other issues all need to be further studied. To this end, in

this study, we selected two kinds of crops stubble (wheat

and soybean) and placed them into continuous cropping

soils of cucumber in greenhouse to study the effect of the

crops stubble on the continuous cropping soils and cu-

cumber growth, so that we can provide scientific basis

and technical methods for solving the problem of con-

tinuous cropping obstacles in protected vegetables.

2. Materials and Methods

2.1. Experimental Materials

Wheat (Triticum aeslivum L.) variety: Kefeng No. 6,

soybean (Glycine max) variety: North 86-4, cucumber

(Cucumis sativus L.) variety: Tianjin Green No. 3.

The tested stubble: Wheat and soybean stubble were

obtained from the residues of previous crops harvested,

including the roots. When the crops stubble was collected,

firstly, the stubble was dug from soil, and then cleaned,

dried, and crushed by the grinder [8]. The physicochemi-

cal properties of the crops stubble were as shown in the

following table (Table 1).

The tested soil: the sampled soil was taken from con-

tinuous cropping soil of cucumber in greenhouse, the

basic physicochemical properties of the sampled soil

prior the experiment were as shown in the following ta-

ble (Table 2).

2.2. Pot Study

Here, studies were done in p ot s in March to August, 2009.

The diameter of pot was 30 cm, 22 cm high, loading 8

kg of soil per pot. First, the soil of continuous cropping

cucumber was sieved through 6 mm sieve to remove lar-

ger clods and the other plant residues etc. Second, the

sieved soils and crushed stubble were uniformly mixed

together according to the different weight ratio (Table 3).

Third, we placed the mixed so ils into pots (8 kg per 30 ×

22 cm pot). Then, these pots were adequately watered,

covered by plastic film to decompose for 21 days in solar

greenhouse. To release some of harmful gases, the plastic

film had been removed for a week when cucumber seed-

lings were planted. The pots were placed on ground in

solar greenhouse as 60 × 30 cm, and 5 g diammonium

phosphate was put into per pot, cucumber seedlings were

planted after three days. The pots without stubble were

used as the controls (CK).

The experiment included a total of 7 treatments (2 kinds

of stubble × 3 kinds of dosage + 1 control). And these

treatments were repeated 3 times, we used 30 pots for

each treatment, making a total of 630 pots.

Table 1. Physicochemical properties of the te ste d stubble.

Tested

stubble Total

carbon (mg· g–1) Total nitrogen

(mg·g–1) Total phosphorus

(mg·g–1) Total potassium

(mg·g–1) C/N

Wheat 328.57 7.38 1.71 9.52 83.63

Soybean 284.67 9.36 1.35 3.54 49.27

Table 2. Physicochemical properties of the tested soils.

Total

nitrogen

(g·kg–1)

Alkalihydrolysible

(mg·kg–1)

Total

hosphorus

(g·kg–1)

Quick acting P

(g·kg–1)

Total

potassium

(g·kg–1)

Quick acting

(g·kg–1)

Organic

matte

(%) pH EC

(ms·cm–1)

2.67 0.292 1.63 0.269 1.16 0.327 1.56 7.661.61

Table 3. The Symbols used for different stubble and quantity.

Stubble Wheat Soybean Control

Adding quantity 0.5% 1% 2% 0.5% 1% 2% 0

Symbol A1 A2 A3 B1 B2 B3 CK

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

2.3. Sampling and Determination

Sampling: We sampled one time per 20 days after the

cucumber seedlings planting, making a total of 3 times.

We randomly selected 3 pots to collect rhizosphere soil

each time, the topsoil in the vicinity of the cucumber

plants was removed before collecting rhizosphere soil.

The soil samples of 3 replications were collected respec-

tively, then mixed, sieved through 2 mm sieve. The soil

samples were air-dried for storage, which were used for

determining physicochemical indicators of the continu-

ous cropping soil and soil enzyme activity.

Soil indicators: Soil pH was determined using the

PHS-2F digital pH meter, Soil EC by using DDS-11A

conductivity, the soil bulk density by using cutting ring,

total porosity of soil was calculated by soil bulk density

(r) and soil proportion (d), the formula is as follows:



11 100%prd 





The soil density was replaced by the mean value of gen-

eral soil, taking 2.65 (g/cm3). The soil moisture was de-

termined using drying weight method, the formula is as

follows:

Soil moisture (%) =







12 2100% 9,10WW WW .

Cucumber yield: Five plants were chosen arbitrarily in

each treatment, and were marked. We recorded yield of

each plant singly, took their average, and then converted

it into the yield of per hectare (hm2).

Cucumber quality: So luble solids were determined us-

ing hand-held sugar meter (Made in Japan), Vc content

by using 2,6-dichlorophenol indophenol titration. Taste

was evaluated by using sensory identification method.

3. Results

3.1. Physicochemical Properties of Soil

3.1.1. Bulk Density and Porosity

Wheat and soybean stubble decreased the bulk density of

soil, and increased soil porosity (Table 4). All wheat

stubble treatments decreased significantly bulk density of

soil, moreover, the bulk density constantly decreased as

the increase of wheat stubble quantity. A2 and A3 had

the larger reduction, but there was no significant differ-

ence between the A2 and A3. Soybean stubble had also

similar effect, but the effect of soybean stubble was

smaller than that of wheat stubble. This shows that two

kinds of crop stubble help to decrease bulk density of soil,

and increase the soil permeability. However, each of

stubble treatments had contrary result on the porosity of

soil. All treatments increased the porosity of soil, more-

over, the porosity constantly increased as the increase of

stubble quantity. 2% wheat stubble had a greatest effect

on the porosity of soil, in creasing by 24.4% than the co n-

trol, and followed by 2% soybean stubble, increasing by

18.96%.

3.1.2. Soi l Moisture

Two kinds of crop stubble had certain effect on soil pH,

but the effect was different in different growth periods

(Figure 1). In the pre-stage of cucumber growth, two

kinds of stubble increased the moisture of soil, wheat

stubble had greater effect on the moisture of soil com-

pared with soybean stubble. The greatest effect was ob-

served in 2% wheat stubble treatment, which increased

the moisture by 26.37% compared with control. Soybean

stubble treatments had similar effects, but these effects

were smaller, in particular, 0.5% soybean stubble had a

minimum effect, which had no difference compared with

the control.

In the medium term, wheat stubble treatment increased

largely the moisture of soil, 2% of wheat stubble had

greatest affect on the moisture, which was significantly

higher than other treatments and control, increased by

34.35% than control. Soybean stubble treatment had also

similar effects, 2% of soybean stubble treatment had

greatest affect on the moisture.

In the later period, all treatments increased the soil

moisture too, but these treatments had lesser increase in

soil moisture.

Table 4. Effect of different treatments on bulk density and porosity of soil.

Treatments Bulk density (g·cm–3) Total porosity (%)

A1 1.21 ± 0.08bc 54.34 ± 6.16c

A2 1.02 ± 0.08d 58.51 ± 8.02b

A3 1.01 ± 0.06d 61.89 ± 6.33a

B1 1.26 ± 0.05b 52.45 ± 4.61cd

B2 1.16 ± 0.07c 56.23 ± 7.12bc

B3 1.12 ± 0.03c 57.74 ± 3.13b

CK 1.41 ± 0.08a 46.79 ± 5.18e

Note: Values are means ± standard deviation. Significant differences (P < 0.05 using Duncan’s multiple range test) among

treatments in the same column are indicated by different letters, the same as below.

Effects of Crop Stubble on Physicochemical Properties of Continuous Cropping Soil and Cucumber Yield and Quality 91

ded

ab b

efe

bc dc

eecd

20 40 60

Days after planting

S oil mo istu re（%）

Figure 1. Effect of different treatments on moisture of soil.

3.1.3. Soil pH

Two kinds of stubble had certain effect on soil pH, but

the effect was relatively smaller (Table 5). In the pre-

stage and mid of growth, most of the stubble treatments

decreased soil pH, only the 2% wheat stubble (A3) in-

creased it. 2% wheat stubble treatment had the greatest

increase in the soil pH, but there was significant differ-

ence between it and control. Other treatments had no

significant di ff erence too.

In the later stage of growth, all stubble treatments de-

creased soil pH but only 2% wheat stubble treatment

increased it. 2% wheat stubble treatment was signifi-

cantly higher than control, while other treatments had on

significant difference compared with control. The maxi-

mum decrease was observed in the 1% soybean stubble

treatment, but it had on significant difference compared

with control.

3.1.4. Soil EC

Two kinds of stubble had relatively larger effect on soil

EC (Table 6). In the pre-stage of cucumber growth, all

wheat stubble treatments significantly decreased soil EC,

a maximum decrease was observed in 1% wheat stubble

treatment, and followed by 0.5% wheat stubble treatment.

Soybean stubble also decreased soil EC, the soil EC val-

ues of all soybean stubble treatments were significantly

lower than the control, 0.5% and 1% of soybean stubble

had greater decrease in soil EC. In the mid-and late,

whether wheat stubble or soybean stubble all showed the

similar laws in soil EC.

3.2. Cucumber Yield

Two kinds of stubble increased yield of cucumber (Fig-

ure 2). All treatments of wheat stubble markedly in-

creased yield of cucumber, the highest yield was ob-

served in 2% wheat stubble treatment, which increased

the yield by 34.23% compared with control. Soybean

stubble increased yield of cucumber too, but soybean

stubble treatment had the smaller increase than wheat

stubble treatment. The higher yield was observed in 1%

soybean stubble treatment, which increased the yield by

16.01% compared with control.

Table 5. Effect of different treatments on soil pH after

planting.

Treatments20 days 40 days 60 days

A1 7.35 ± 0.04ab 7.35 ± 0.08ab 7.33 ± 0.16bc

A2 7.34 ± 0.14ab 7.47 ± 0.17ab 7.27 ± 0.14bc

A3 7.77 ± 0.16a 7.73 ± 0.06a 7.66 ± 0.05a

B1 7.62 ± 0.06a 7.38 ± 0.03ab 7.34 ± 0.05bc

B2 7.41 ± 0.12ab 7.35 ± 0.05ab 7.26 ± 0.03bc

B3 7.21 ± 0.09b 7.30 ± 0.06ab 7.28 ± 0.08bc

CK 7.61 ± 0.08a 7.65 ± 0.11a 7.49 ± 0.11b

Table 6. Effect of different treatments on soil EC after

planting (ms/cm).

Treatments20 days 40 days 60 days

A1 0.79 ± 0.04f 1.07 ± 0.06e 0.82 ± 0.03f

A2 0.73 ± 0.07cd 1.04 ± 0.07e 0.88 ± 0.06ef

A3 0.97 ± 0.02e 1.01 ± 0.04e 0.80 ± 0.06f

B1 1.14 ± 0.09c 1.13 ± 0.06d 0.93 ± 0.08e

B2 1.16 ± 0.07c 1.16 ± 0.05d 1.38 ± 0.03b

B3 1.24 ± 0. 0 8b 1.37 ± 0.09c 1.25 ± 0.04c

CK 1.62 ± 0.03a 1.72 ± 0.01a 1.66 ± 0.05a

ede

20000

40000

60000

80000

100000

treatments

Yield（kg. hm-2）

Yield (kg·hm

-2

)

Figure 2. Effect of different treatments on the yield of cu-

cumber.

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

3.3. Cucumber Quality

As can be seen from Table 7, wheat stubble significantly

improved cucumber quality. First, wheat stubble in-

creased the content of dry matter, moreover, the content

of dry matter gradually increased as the increase of wheat

stubble quantity. Second, wheat stubble increased the

content of vitamin C and soluble solids in fruits, but

0.5% wheat stubble treatment had no difference com-

pared with the control. Third, wheat stubble decreased

the incidence of deformed fruits. The greatest decrease

was observed in 2% wheat stubble treatment, and fol-

lowed by 1% wheat stu bbl e t reat ment.

Soybean stubble had certain effect in improving fruit

quality too. 0.5% and 1% of soybean stubble treatments

increased the content of dry matter, while an opposite

result was observed in 2% of treatment. Soybean stubble

had no obvious regularity on the content of vitamin C

and soluble solids in fruits, which was sometimes as-

cending and sometimes descending. 0.5% of soybean

stubble treatment significantly increased the content of

vitamin C in fruits, but it h ad a little effect on the soluble

solids. 2% of soybean stubble treatment decreased the

incidence of deformed fruits, which was significantly

lower than control.

4. Conclusions

Many studies showed that organic materials decreased

soil bulk density, increased total porosity, increased soil

aggregate structur e, and impro v ed soil permeab ility when

they were added into soil [9,10]. At the same time, or-

ganic materials could increase soil pH, and lower soil EC,

even that they could improve the physicochemical prop-

erties [11,12].

In this test, whether wheat stubble or soybean stubble

obviously decreased soil EC, especially in the later pe-

riod, the decrease of soil EC was greater. Each of all

treatments significantly decreased the salinity accumula-

tion in soil within the entire growth period of cucumber,

a maximum decrease of the EC was observed in 2%

wheat stubble treatment, while effect of two kinds of

stubble on soil pH was not obvious. This may be related

to the microbial metabolism, because the stubble can

provide more nutrients for the microorganisms in soil,

and promote the activity of microorganisms. Thus, wheat

or soybean stubble can reduce continuous cropping ob-

stacle in greenhouse soil. For example, when two kinds

of stubble are added into the continuous cropping soil,

many of the problems such as soil compaction, staliniza-

tion, poor permeability and poor water holding capacity,

even some soil sickness will be solved . Therefore, wheat

stubble or soybean stubble has a positive effect in pro-

moting cucumber growth and improving sick soil.

Soil moisture is an important indicator related to soil

microorganism activity and crop growth, which directly

affects the growth and yied of crops. According to re-

search report [13,14], straw returning en hanced the abili-

ties for soil to retain water and nutrients, increase capac-

ity of holding water, and improve the effectiveness of

natural precipitation. Wang [15] (2000) studied the ef-

fects of straw for different processing methods on soil

moisture, the results showed that straw returning im-

proved soil moisture condition s, increased the cap acity o f

water storage and water retention in soil.

In this test, the results showed that two kinds of stub-

ble increased soil moisture, while the effect of wheat

stubble on soil moisture was greater than that of soybean

stubble, and 2% of wheat stubble had greatest effect,

which increased soil moisture by 26.37% compared with

control. One of the main reasons is that the density of

wheat stubble is smaller than that of soybean stubble, so

the volume of wheat stubble is relatively larger than that

of soybean stubble. Therefore, wheat stubble treatment

has greater increase on soil total porosity than soybean

stubble, so wheat stubble is more conducive to increase

the soil moisture. In addition, because the density of

Table 7. Effect of different treatments on the quality of cucumber.

Treatment Deformed fruits r ate (%) Dry matter

(%) Vitamin C

(mg/100g FW) Soluble solids (%) Taste

A1 9.32 ± 0.13c 3.15 ± 0.08cd 9.85 ± 0.09e 7.6 ± 0.06d Good

A2 6.33 ± 0.08e 3.84 ± 0.06b 12.23 ± 0.13b 9.1 ± 0.09a Excellent

A3 5.57 ± 0.06ef 3.96 ± 0.11ab 13.22 ± 0.15a 8.9 ± 0.06ab Excellent

B1 9.01 ± 0.16c 3.33 ± 0.10c 12.37 ± 0.18b 8.1 ± 0.12b Good

B2 8.33 ± 0.06d 3.37 ± 0.04c 10.58 ± 0 .12d 7.9 ± 0.07b Excell e n t

B3 11.28 ± 0.09 a 2.26 ± 0.06ef 10.59 ± 0.11d 7.5 ± 0.10d Good

CK 9.67 ± 0.11c 2.63 ± 0.07e 9.66 ± 0.07e 7.8 ± 0.11d General

Effects of Crop Stubble on Physicochemical Properties of Continuous Cropping Soil and Cucumber Yield and Quality 93

wheat stubble is smaller than that of soybean stubble, so

more wheat stubble was floated on the water when wa-

tering, and it was just attached to the soil surface after the

water seeping down, thus wheat stubble treatment can

decrease water evaporation, and relatively increase the

soil moisture. This may be another reason that the wheat

stubble is more conducive to increase the soil moisture.

According to studies, there are three major reasons on

continuous cropping obstacle of cucumber: First, the

nutrients in soil were in imbalance, the physicochemical

properties of soil became worse. Second, the pathogens

in soil proliferated quickly, the ecological environments

of microorganisms were destroyed, and the biological

properties of soil became worse. Third, it is due to the

allelopathy of the root exudates and the stubble decom-

position [5,16,17 ]. It is exactly effective ways and meas-

ures for Mixed intercropping, crop rotation and the de-

velopment and application of soil remediation agents to

solve this problem. According to the investigation, straw

return can promote the growth of crops, increase crop

yields by 5% - 10% [18,19]. According to another report,

organic material also can increase cucumber yields when

it was added into soil in the greenhouse [4,20]. In our

experiment, wheat and soybean stubble promoted the

growth of cucumber, increased yield of cucumber. Among,

1% and 2% of wheat stubble markedly increased yield of

cucumber, the highest increase of yield was observed in

2% wheat stubble treatment, which increased the yield by

34.23% compared with control. Thus, two kinds of crop

stubble can coordinate the water, gas, heat, nutrient and

other condition s in soil, impro ve the physicoche mical pro-

perties of soil. So, this helps to establish a good founda-

tion for cucumber growth and yield increase. In our ex-

periment, the wheat and soybean stubble increased soil

moisture, this may be one of the important reasons wh ich

caused the increase of cucumber growth and yield.

5. Conclusion

Wheat and soybean stubble all obviously decreased the

soil EC, while the effect of two kinds of stubble on soil

pH was not obvious. Two kinds of stubble increased soil

moisture and porosity, in which th e effect of wheat stub-

ble was more remarkable than that of soybean stubble. At

the same time, wheat and soybean stubble promoted the

growth of cucumber, increased the yield of cucumber,

and improved the quality of cucumber. This shows that

wheat and soybean stubble can improve the physico-

chemical properties in continuous cropping soil, and re-

duce continuous cropping obstacles of cucumber.

6. Acknowledgements

This project was financially supported by Introducing

Innovation Talent Fund of Jilin Province. Here, I express

my heartfelt thanks for them.

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