Characteristics of Soil Nutrients in Farmland in the Paddyupland Rotation Region of Chengdu Plain-a Case Study of Pidu District, Chengdu CityWang Bin
Research Institute of Subtropical Forestry,
Chinese Academy of Forestry
2018.08.27

Contents

I.

Description of Paddy-upland Rotation

II. Paddy-upland Rotation of Pidu District, Chengdu City
III. Characteristics of Soil Nutrients in Farmland
IV. Spatial Distribution of Soil nutrients
V. Discussion

I. Introduction of Paddy-upland Rotation
1 Paddy-upland Rotation and Multiple Cropping
Multiple Cropping （such as continuous cropping and crop rotation ） Han Dynasty（202-220 BC）：Multiple cropping had been well documented
 Song Dynasty（960-1276）： Multiple cropping rotation plays an important role inagricultural production（ wheat-rice double cropping, double cropping rice ）Paddy-upland Rotation （such as multiple cropping of rice and wheat ） Tang Dynasty（618-907）： Paddy-upland rotation had been well documented inhistory of Yunnan
 Song Dynasty（960-1276）：It appeared but was not common in Yangtze-Huaiheriver basin
 Song and Yuan Dynasties（960-1368）： A variety of forms was formed

2 Ecology Significance of Paddy-upland Rotation
A biological measure combined with land use andland maintenance；• Has a balanced use of soil nutrients；• Increase the yield per unit area;• Improve soil physical and chemical properties；• Adjust soil fertility；• Control insect pests.

Paddy Field

Upland Field

II. Paddy-upland Rotation of Pidu District
1 Introduction of Pidu District•••

Area：438 km2
Sichuan Province
Population：60.09×104
Farmland area：2×104 hm2

Chengdu CityPidu District

2 Characteristics of Ecological Environment• Located in the alluvial plain of the Minjiang River;• Has abundant rainfall and four distinct seasons;• Belongs to Dujiangyan irrigation area with a rich Irrigation and drainage system;• It slopes from northwest to southeast, the relative height is no more than 2m;• Soil is paddy soil and suitable for all kinds of crops.
Dujiangyan

Chengdu City

3 Planting Patterns
1）Paddy-upland Rotation

Rice-rape

Rice-garlic

Rice-round carrot

Rice-potato

Rice-mustard

Rice-broccoli

2）Dry Farming

Plant leeks ----

Cover the roots ----

Harvest leeks and leek shootsContinuous cropping of leeksContinuous cropping of lettuce

Crop rotation of water spinach, flower Chinese cabbage and mustard

Geographical Indication Products

Tangyuan Leek ShootYunqiao Round Carrot

Deyuan Garlic4 Purpose of This Research• Analyze the soil nutrient contents and spatial distribution under the background ofhigh-intensity land use in Pidu district;• Discuss the effects of various factors on spatial variation of soil nutrient contents;• Provide reference for regional agriculture sustainable management and ecologicalenvironment protection.

III. Characteristics of Soil Nutrients in Pidu District
1 Data sources• Soil testing data before fertilizing in 2015, including pH, soil organic matter(SOM), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP)and available potassium (AK);• Farm survey data, including soil conditions, plant crops, yield and fertilization;• After removing the outliers, 287 effective data were obtained.

Sampling Site

Farm survey

2 Descriptive Statistics Characteristics of Soil Nutrients• The median of 5 soil indices was lower than the mean, and the skewness was greaterthan 0, with the distribution belonged to right skewness.
• The CV of TN is less than 0.25, showing its little change in the region; the CV ofSOM, AN, AP and AK is between 0.25 and 0.5, indicating certain differences in theregion, but not significant.

• The analysis of the data normality shows that the AN conforms to normal distribution.
SOM, TN, AP and AK also conform to normal distribution after log-transformation,
which meet the needs of statistics analysis and spatial interpolation.
Nutrients

Numbers

Minimum

MedianMaximum

MeanSDCVSkewness

Distribution type

SOM

287

12.12

21.40

39.30

22.35

5.99

0.27

0.61

Log normal

TN287

0.75

1.06

2.04

1.15

0.24

0.21

0.92

Log normal

AN287

40.50

95.00

149.00

95.38

24.12

0.25

0.06

Normal

AP

287

10.26

19.40

42.00

21.01

5.22

0.25

1.54

Log normal

AK287

48.00

92.00

205.00104.58

41.71

0.40

0.63

Log normal

Note: The unit of SOM and TN content is g/kg, and the unit of other elements contents is mg/kg.

3 Proportion of different grade soil nutrient
According to the national second soil census nutrient grade classification standard,• AP is higher and the ratio of moderate level above achieves 100%;• TN and AN are common and the ratio of moderate level above is about 65%.
• AK content is low, only about 44% of it reaches moderate above level.
• In general, the soil nutrients in the farmland of Pidu District are not superior, and theproportion of soil nutrient deficiency is still quite large.
RichLess richModerate

Less deficient

Deficient

Nutrients
Content Ratio(%) Content Ratio(%) Content Ratio(%) Content Ratio(%) Content Ratio(%)
TN＞20.67＞1.5~29.33＞1~1.555＞0.75~134.67

≤0.75

0.33

AN＞1500＞120~150

18＞90~120

47＞60~90

26.33

≤60

8.67

AP＞400＞20~40

45.33＞10~2054.67＞5~100≤50AK＞200

1.33＞150~200

17＞100~150

26＞50~100

54.34

≤50

1.33

Note: The unit of SOM and TN content is g/kg, and the unit of other elements contents is mg/kg.

4 Difference of Different Soil Types









CMSS: Calcareous moisture sandy soil
CMS: Calcareous moisture soil
CAS: Calcareous alluvial large clay
CALOSS: Calcareous alluvial large oil sandy soil
CAOSS: Calcareous alluvial oil sandy soil
CASS: Calcareous alluvial sandy soil
GMC: Grey-brown moisture clay
GMSC: Gray-brown moisture sandy clay

There is a certain difference between SOM and TN; there is no significant difference
between AN and AP; AK has the biggest difference.

5 Difference of Different Planting Patterns








CCL: Continuous cropping of leeks
CCV: Continuous cropping or Crop rotation ofvegetables
RV1: Rape-vegetables
RC: Rape-corn
RR: Rice-rape
RV2: Rice-vegetables
RG: Rice-garlic
RRC: Rice-round carrot

No significant difference between SOM, TN and AN; a certain difference between AP and AK;• The pattern of CCL has high requirements on soil nutrient content, especially on AP; RRC has highrequirements on AP; and RG has high requirements on AK.
• The requirements for soil nutrient content in RV1 and RC are lower than those of other models.

6 Correlation Analysis of Different Soil Nutrients• There was a significant positive correlation between SOM and AN and AP,indicating that the accumulation and decomposition of SOM had an
important effect on the distribution of AN and AP in soil.
• AN was positively correlated with AP and AK, and was related to theextensive application of compound fertilizer in this area.
Indicator

SOMTN

ANAP

AKSOM

1-0.034

0.192**

0.936**-0.08

1-0.064-0.0560.011

10.156*0.220*

1-0.057

TNANAP
AK1

IV. Spatial Distribution of Soil nutrients
1 Research method
The ArcGIS geostatistical module is used to select the optimal semi-variogram function
model, and the interpolation is performed by the ordinary Kriging method.
The model selection follows the following principle:• ME is closest to 0;• RMS is the smallest and closest to ASE;
• RMSS is closest to 1.

2 Best semi-variance models and the related parameters
Nutrients

ModelNugget

Partial sill Nugget/sill Range/m

MERMS

ASE RMSS

SOM

Spherical

15.025438.81780.39

608.960.00346.31596.57450.9600TN

Gaussian

0.05950.06840.87

608.960.0016

0.26290.27770.9470ANExponential

582.7442

618.30520.94

8824.40-0.0085 24.4842 25.0947 0.9767

AP

Exponential

28.531429.33530.97

6336.49-0.0001

AKExponential

1171.2597

1877.7269

0.62

1053.430.0051 44.3653 45.1361 0.9833

5.37665.52990.9733

 Nugget coefficient = nugget value/sill: reflect the level of data spatial correlation, thevalue is smaller and the correlation is stronger; Structural factors: soil parent material, topography and landform, altitude, climate, etc;
 Random factors: farming system, fertilization status, distance from residential areas, etc;
 SOM(0.39): structural factors play an important role in its spatial distribution;
 AK(0.62): structural factors and random factors are combined; TN, AN and AP: random factors play a decisive role.

3 Spatial distribution•

SOMTN•••ANAP

The spatial distribution of SOM
and TN is generally similar, withsome higher areas;
The south part of AN is higher;
The north part of AP is higher;
Part area of AK is higher.

AKIt can be seen that the AN in Xinminchang Town has a good correspondence with theradish plantation in this area; it is same with the AK in Deyuan Town with the garlicplantation and AP in Tangyuan Town with the leek plantation.
ANDistribution of Planting PatternsAP

Yunqiao Round Carrot
Tangyuan Leek ShootAK

1 CCL-Continuous cropping of leeks
2 CCV-Continuous cropping or Crop
rotation of vegetables
3 RG-Rice-garlic
4 RRC-Rice-round carrot
5 RV2-Rice-vegetables
6 RC-Rape-corn
7 RV1-Rape-vegetables
8 RR-Rice-rape

Deyuan GarlicThis distribution pattern of farmland soil nutrients in the study
area has a certain correlation with the traditional planting patternsof the towns and villages in the Pidu District.

V. Discussion
1 Characteristics of Soil Nutrients in Farmland① The analysis of variance showed that the soil nutrient content differenceof different soil types and different planting patterns in Pidu District
was small in general, indicating that the soil nutrient content offarmland in Pidu District was relatively consistent due to the highintensity human production activities.

② The soil nutrient content is common, and AK is relatively deficient,which has a certain relationship with the unique soil parent material,
long-term paddy-upland rotation and high multiple crop index in thisarea. In order to maintain the soil fertility of the farmland, the use offertilizer in the Pidu District has shown a significant uptrend in recentyears. The use of P2O5 and K2O has increased by 3-4 times in the past
10 years. We can see that the high production of farmland in the Pidu
District currently is based on the large use of fertilizer.
25
21.41
20
15

Fertilizer Use（kg/Mu）
2008

19.12

2015
14.72

12.71

10
4.99
5

5.52

0N

P2O5K2O2 Spatial Distribution of Soil nutrients① According to the results of different
research, the nugget coefficient of
SOM in the farmland of Pidu
district showed a declining trend,
while TN, AN and AP showed anincreasing trend.
② This change maybe related to thechanges of planting patterns suchas vegetable-based dry farming
instead of traditional paddy-uplandrotation and compound fertilizer
instead of farmyard manure.

ItemSOM

TN

AN

APAK

Year

Content Nugget/sill

Reference

1982

25.65

0.810

杨刚，2012

2004

15.60

0.640

秦鱼生，2008

2007

33.04

0.720

杨刚，2012

2015

22.35

0.390

This research20021.29

0.436

陈肖，2007

2016

1.94

0.524

张浩，20182015

1.150.870

This research

2002

72.20

0.377

陈肖，20072016

138.700.639

张浩，2018

2015

95.38

0.940

This research

1982

7.100.700

肖鹏飞，2005

2002

14.30

0.790

肖鹏飞，2005

2004

8.23

0.633

秦鱼生，2008

2015

21.01

0.970

This research

2004

72.20

83.600秦鱼生，2008

2015

104.580.620

本研究

③ In addition, the spatial distribution of different soil nutrient contents inthe study area has a certain correlation with the spatial distribution ofdifferent planting patterns in the area, which shows that the demand offarmland crops for nutrients also affects the spatial distribution pattern ofsoil nutrients in some way.

Thanks！