Soil Nutrients and pH in Rapeseed Planting Areas in the Middle Reaches of the Yangtze River Based on GIS
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    Abstract:

    【Objective】Rapeseed is one of the most important oil crops in China, and the Yangtze River Valley is a major oilseed rape production region of the country, accounting for over 20% of the world’s mean of annual rapeseed planting area and total rapeseed yield. Farmers in the Yangtze River Valley plant two or three crops a year to form a rotation system. Rapeseed is planted in winter in rotation with rice, cotton or soybeans. As a result of such an intensive cropping system, the farmlands are quickly deprived of soil nutrients and do not have enough time to get recovered in soil fertility. Besides, farmers apply nitrogen (N), phosphorus (P), potassium (K) and boron (B) fertilizers randomly without taking into account the demands of the crops for nutrients. Consequently, the farmlands vary sharply in soil fertility or soil nutrient content from area to area. In this paper an attempt has been made to explore characteristics of the spatial distribution of soil nutrients and pH as affected by crop rotation system and area in the middle reaches of the Yangtze River Valley with the aid of geostatistics and GIS technology, so as to provide some technical support to the efforts of establishing a region-scaled scientific fertilization system for the crop of rapeseed aiming at high yield, high efficiency and eco-environment safety, and realizing sustainable development of the agriculture in the region. 【Method】Based on the database of the soil survey and sampling carried out in Hubei, Hunan and Jiangxi provinces during the period of 2013-2014, a total of 5463 soil samples collected from these provinces were analyzed for six soil indices, such as soil organic matter (SOM), total N (TN), available P (AP), available K (AK), available B (AB), and soil pH. With the aid of the GIS platform and Kriging method, the farmlands in these provinces were evaluated and sorted into six grades by referring to the standards for grading of the six indices set for the Second National Soil Survey. In the light of complicate topography and high diversity of soil types, the region was divided into four cropping zones, i.e., plain area with double cropping system (PII), mountain area with double cropping system (MII), plain area with triple cropping system (PIII), and mountain area with triple cropping system (MIII). 【Result】Results show that SOM, TN, and AP contents were obviously higher in the areas with triple cropping system than in those with double cropping system, which is attributed to the higher multiple cropping index of the former and resultant higher root residue in the field, increasing SOM. Especially in MIII, SOM, TN and AP reached as high as 28.8 g kg-1, 1.60 g kg-1 and 16.2 mg kg-1, respectively. In terms of SOM, 63.3%~76.1% of the farmlands were sorted into Grade III; in terms of soil TN, about 90.2% or 11 061 000 hm2 were in Grade II (1.5~2.0 g kg-1) and III (1.0~1.5 g kg-1); in terms of soil AP, 70.2% or up to 8 601 000 hm2 of the farmlands were in Grade III (10~20 mg kg-1), and 17.5% and 12.3%, in Grade II and Grade IV, respectively. Soil AK did not vary much between zones, ranging from 93.6 to 95.8 mg kg-1. However, the region still had 182 000 hm2of farmlands deficient in K (<50 mg kg-1). Soil AB did not either, ranging from 0.42 to 0.47 mg kg-1. It is quite clear that measures should be taken to raise soil AB content in the region, especially in the areas with triple cropping system, where about 13.6%~20.4% of the farmlands were in Grades V and VI. According to the standard for grading in the Second National Soil Survey, the region was quite high and could be sorted into Grades II and III in SOM, TN, and AP, but quite low and in Grade IV in soil AK and AB. Most of the farmlands in the region were around 6.0 in soil pH, but in areas with triple cropping system, a relatively high proportion or about 35.7% of the farmlands varied in the range of 4.5~5.5 in soil pH. 【Conclusion】To sum up, in the middle reaches of the Yangtze River Valley, soil nutrient status varies from area to area. Especially in the areas with triple cropping system, quite a large proportion of farmlands need to be raised in soil boron content and ameliorated in soil acidity.

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CONG Rihuan, ZHANG Zhi, ZHENG Lei, MIAO Jie, REN Yi, Ren Tao, LI Xiaokun, LU Jianwei. Soil Nutrients and pH in Rapeseed Planting Areas in the Middle Reaches of the Yangtze River Based on GIS[J]. Acta Pedologica Sinica,2016,53(5):1213-1224.

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History
  • Received:December 20,2015
  • Revised:April 30,2016
  • Adopted:May 12,2016
  • Online: June 28,2016
  • Published: