Typical farmland soil fertility ascending mechanism research in guangdong province
Yankai chen
(College of resources and enviroument, South China Agricultural University, Guangzhou 510642, China)
Abstract: Natural quality is not high, cultivated land resources in our country is limited.Although we do a lot of work to improve soil, soil still accounts for most of the arable land area, but now the middle reach 2/3.Since the second soil census, organic matter content in most of the farmland in China has improved, but the overall level is not high, the average content is low, only about European and American developed countries generally.With the improvement of farmland intensive utilization degree, a large number of large-scale planting farm sprang up, a large number of agricultural chemicals and the popularity of large machines, and cause a lot of new soil problems, such as soil compaction, structure degradation, aggregate stability decreased, soil biological degradation function, reduced water raise buffering capacity etc, is one of the most important content of soil organic carbon and reduce the stability of the aggregate.Generally takes up high quality cultivated land, cultivated land occupancy and the increasing number of cultivated land is often inferior exacerbate the problem of farmland soil fertility decline.This study by collecting different typical area of guangdong province farmland soil fertility level, through the analysis of components, quality and distribution of soil organic matter content, soil aggregate characteristics and its influencing factors, explore can represent basic farmland soil indicator of soil fertility, improve the key by reveal limit soil processes and factors, looking for effective regulation pathway;Through the regulation of organic matter transformation process and its driving factors in increasing soil organic matter accumulation;Finally realize the ascension of farmland soil fertility, increasing food production, improve the quality of the food.
Keywords: Typical farmland、soil fertility、Ascending mechanism、Soil quality
1 Introduction: Farmland soil organic matter content of the large area appears lower in our country[1], the variation of soil physical and chemical properties, soil fertility decline trend.Soil aggregate is the basis of the formation of soil structure, soil is "keep depots".Research shows that, the higher the farmland foundation soil, in the same variety, dosage and control measures of water production and resource use efficiency is higher[2].So, to dig up effect of foundation soil fertility promoted, promote the yield and the cultivated land resource use efficiency, carry out the mechanism of promoting farmland soil fertility and directional cultivation countermeasure research, to improve soil fertility of large middle-and-low-yielding fields to provide theoretical and technical support.Through revealing limit soil fertility improving key process and factors, looking for effective regulation pathway;Through the regulation of organic matter transformation process and its driving factors in increasing soil organic matter accumulation;Finally realize the ascension of farmland soil fertility.To investigate the characteristics of soil structure and organic matter, provide the basis for farmland to raise soil fertility and keep[4].
2.1 The definition of farmland soil fertility contribution and significance
Soil contribution refers to no fertilizer treatment crop yield of fertilizing crops yield percentage, is an important index of soil fertility.Ratio the higher the soil fertility[4], soil fertility level is higher, the lower the dependence on fertilizers to crops
2.2 Farmland index of soil fertility
2.2.1 Physical and chemical index of farmland soil fertility
Soil organic matter is one of the most important chemical indexes of farmland soil fertility.Except as a source of nutrition[5], it can improve soil structure and water holding capacity and improve the biological activity.It through the transformation equation to calculate the soil bulk density, water holding capacity, leaching potential, ion exchange capacity (CEC) and soil productivity.
On soil pH, conductivity, the assessment of CEC and nutrient content of farmland soil chemistry is necessary, because they provide a can reflect the soil nutrients and an improved ability to buffer the chemical measurement indicators[6].PH can affect a lot of the relationship between soil biological properties and chemical properties.Ion exchange capacity is the ability evaluation of soil conservation and nutrients important attribute.
Foundation soil physical quality index in the quality differences between the soil type is very useful.Soil physical properties of soil texture is the most basic, it can control the moisture, nutrients and gas exchange, maintain and absorption.Soil layer thickness is affected plants per unit area of quantitative properties of the number of available resources.
Soil bulk density with the organic matter content of the soil texture, structure, and different variation is very big[7].But, for a specific soil type, density can be used for monitoring soil compaction degree.The change of soil bulk density besides itself affects the moisture and oxygen supply, may also affect many other properties and process.The soil strength is measured by cone penetrometer can be used as an index of soil compaction.
Moisture permeability, maintain, availability, drainage and indexes for the comprehensive monitoring soil moisture balance[8].Function is very important.Effective capacity according to the relative strength of the soil water supply.Saturated moisture conductivity is an index reflecting soil drainage speed, can be used to determine soil moisture balance[9].
Soil structure is refers to the organic matter and other chemical sediment size and shape of the binding together of aggregate.It can affect almost all the physical, chemical and biological properties of soil.The stability of the aggregate can be used to describe when soil under different pressure maintain ability of the proportion of solid phase and liquid phase[10].Due to soil aggregate can reflect the soil biological properties, chemical properties and the relationship between physical properties, so the soil aggregate is a very important quality index.Narrow and Coen_9 points out that the crop and soil management practices on soil physical quality influence soil aggregate can be used to describe the size distribution and stability[11].
2.2.2 Biological indicators of farmland soil fertility
Due to have a simple and feasible method, early farmland soil fertility evaluation focuses on the physical and chemical properties of the soil.However, soil physical and chemical properties as indicators of farmland soil fertility sometimes can not evaluate the effects of soil management and land use.
Farmland soil fertility evaluation in recent years, more attention paid to the biological indicators, biological indicators including soil on the growth of plants, soil animals and soil microbes, which applied the most were soil microbial indicators.Soil microbial research is divided into three levels: population level, community level, ecological system level, ecological system level research is considered to be the best possible ways of fast evaluating farmland soil fertility changes, most studies suggest that soil microorganisms (including microbial biomass, soil respiration) is the most sensitive indicator of farmland soil fertility changes.Soil animal is the important instructions of soil environmental quality and health quality characteristics, especially invertebrates such as nematodes, earthworms can sensitively reflect the poisonous substance content in soil.With plants as the farmland soil fertility evaluation index, mainly on plant growth, production pattern, the structure of the root system, plant tissue characteristics, dominant species of herbage species diversity and weeds, and the evaluation of soil fertility quality and environmental quality and health quality[12].
Kennedv PapendickJ and points out that soil biological properties and biological chemical can be used as indicators to reflect the actual changes in agricultural ecosystem and soil productivity.Soil microbial properties can promote a lot of the change process of soil physical and chemical properties.Microbial activity was also involved in the decomposition[13].Nutrient and energy circulation, the formation and transformation of organic matter of soil aggregate control process, etc.
Soil microbial biomass was proved to be a stable and reliable parameters to do regional scale of quantitative analysis, sampling in vegetative growth late or early spring.It can be used as potential balance of farmland soil fertility index indicating levels of soil organic matter, and the trend of the future, can also be used for long-term monitoring of farmland soil fertility.Previous studies focused on the microscopic scales and soil nutrient cycling and farmland soil microbial activity of related research.However, the spatial distribution of soil microbial biomass on landscape scale analysis and study of the very few[14].Control of soil microbial activity of organic carbon conversion process and migration research helps to evaluate the function of the regional soil resources.Comprehensive microbial indicators have been chosen for farmland productivity potential index, and under the background of soil physical and chemical properties are analyzed.
Soil enzyme activity was used to evaluate the soil fertility at first, has recently been chosen for the potential of farmland soil fertility index.The activity of soil enzymes play an important role in nutrient cycling and has been used as microbial activity index.Enzyme activity can become a good farmland soil fertility index because it in decomposition and plays an important role in the process of mineralization and is sensitive to soil management measures change reaction.
2.2.3 The farmland soil physical, chemical and biological indicators between the relationship
Soil microbial biomass, soil respiration and soil chemical properties there is close relationship between.Relevant research focused on the soil fertility or space of the farmland soil fertility index analysis, studied on landscape scale of farmland soil fertility index variation, very few studies on the regional scale.Other studies focus on the microbial activity on landscape scale spatial distribution, such as carbon mineralization and soil enzyme activities.Current regional variation on soil microbial research focused on the population level, according to the climate gradient using conventional statistical method to study the biological geographical pattern of the microbial diversity.Further work need to study spatial autocorrelation of soil properties and the time stability of the covariance, and topographical features, soil physical and chemical properties and the function of the correlation between soil microbial activity[15].
3 The prospect of research of farmland soil fertility
Farmland soil fertility is a very comprehensive concept, involved in soil science, land use, agricultural cultivation measures and management, and many other aspects.So, need a lot of research fields.At present, the farmland soil fertility studies have focused on farmland soil fertility status of the investigation and analysis, the theory and method of farmland soil fertility evaluation and index system, the cause of the change of soil fertility of farmland and farmland soil dynamic monitoring and forecasting warning and countermeasure, etc., summarizes the latest progress in the study of the current international farmland soil fertility, combined with the actual situation of our country, the farmland soil fertility research should strengthen the following several aspects:
3.1 Farmland soil fertility index and evaluation method
Different scales research problem, need to use different technology was developed for the determination of different indicators.Which requires the development of the field scale indicators, in turn, provide timely information for farmers, in addition to also want to develop regional scale indicators to monitor the quality of soil resources development trend[16].
3.2 Farmland soil fertility change condition, process, influencing factors and mechanism and regularity of time and space.
Focus on land use change, the organic connection between farmland soil fertility and soil microbial environment and its inherent law of research[17].To explore the relationship between the change of land use and soil microbial diversity, and reveals the impact of land use change on farmland soil mechanism and law of this for the recovery of degraded land and regional land resources management and sustainable utilization of land has the vital significance.
3.2 Farmland soil fertility and improve approaches and key technologies
Not only is the composition of the soil minerals, it is minerals, microorganism, root system secretions, water sports and collection of non-biological and biological dynamic process[18].To improve farmland soil fertility must extend interactions between the soil research, mainly in the root growth dynamic response to fertilizer and other measures, the water use efficiency of different system, simple method, the selection of time and space variation of soil nutrient test as farmland soil fertility index, etc.
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