How Land Use Policies Are Transforming Shifting Cultivation to Short Fallow Systems and Permanent Cultivation of Annual Crops in Tanzania

Recent studies show that shifting cultivation in Tanzania has transformed into more intensive farming practices. One of the drivers of this shift is the implementation of policies that favor sedentary farming. However, there is inadequate information on how this transformation operates at the village level. Based on a case study of one village in Central Tanzania, this study demonstrates that the village land use plan is the primary policy tool for the transformation and intensification of shifting cultivation at the village level. Through the land use planning process, land is allocated only for lawful uses such as settlement, permanent cultivation, and the village forest reserve. No land is designated for shifting cultivation. Additionally, the land use plans are accompanied by by-laws that restrict shifting cultivation practices, such as the use of fire during land preparation and leaving the land fallow for more than 3 years. The intensification of shifting cultivation was not associated with an increase in the use of farm inputs such as improved seeds, fertilizer, or irrigation, as is commonly practiced in sustainable intensive agriculture. Instead, it was associated with the adoption of short fallow farming systems and labor-intensive land preparation methods, such as deep plowing to loosen the soil and sub-soiling vegetation.

A Review and Implication of Land Fallow System Research

Land fallow is of great significance for undertaking land reclamation, safeguarding national food security, promoting environmental improvements and ensuring the sustainable use of land resources. This paper reviews the important achievements in three areas of research on the land fallow system. It reviews and compares the land fallow system in different countries and regions of the world; it examines the response of farmers to the land fallow system and ecological environment; and it looks at the economic effects of the land fallow system. Based on Chi- na＇s rotation system for cultivated land, some relevant policy implications are put forward. Based on the different degrees of land damage, the evaluation system and the subsidy accounting standard for fallow land are formulated, and the compulsory fallow and voluntary participation of the niche fallow are targeting. The land fallow system should improve both the regulatory and the restraint mechanisms, improve the environmental awareness and en- vironmental protection skills of farmers, change the production behaviors of farmers, and encourage farmers to change to high coverage crops to protect the land. In view of the negative effects produced by implementation of the fallow system should take corresponding management and compensation measures.

Divergent responses of tiller and grain yield to fertilization and fallow precipitation:Insights from a 28-year long-term experiment in a semiarid winter wheat system

Tillering is an important phenological stage,which is strongly related to the yield in spike components and final grain yield during winter wheat growth.Precipitation during the fallow season(fallow precipitation)influences tillering in winter wheat on the semi-arid Chinese Loess Plateau.However,little work has been done regarding tiller number changes under various types of fertilization and amounts of fallow precipitation on a long-term scale.Effects of fallow precipitation and fertilization on tiller were investigated in a winter wheat(Triticum aestivum L.)system in a 28-year field study(1990 to 2017)in a semiarid agro-ecosystem.Tiller number,spike number and grain yield were measured in four fertilization conditions:control without fertilizer(CK);mineral nitrogen fertilizer alone(N);mineral phosphorus fertilizer alone(P);mineral nitrogen and phosphorus fertilizer together(NP).Based on the long-term annual fallow precipitation,dry years(mean annual fallow precipitation)were distinguished.Phosphorus fertilization alone significantly increased the mean annual tiller number(23%),and the increase in tiller number was higher in wet years(29%)than in the dry years(17%).However,nitrogen fertilization alone had little effect on mean tiller number,while nitrogen and phosphorus together significantly increased mean annual tiller number(30%),mean tiller number in wet years(45%)and mean tiller number in dry years(17%).Tiller number was significantly and positively correlated with fallow precipitation in dry years for all fertilizer treatments,whereas it was weakly and either positively or negatively correlated with fallow precipitation in wet years depending on the treatment.This study found positive correlations between tiller number and fallow precipitation in the CK and NP treatments,and it found negative correlations between tiller number and fallow precipitation in the treatments with nitrogen fertilization alone or phosphorous fertilization alone in wet years.Understanding the impacts of fallow precipitation and fertilization on tiller development shed light on ways to improve crop production in rain-fed agricultural regions.

Estimating Carbon Capture Potential of Fallow Weeds in Rice Cropping Systems

Weeds occurred during the fallow season can well perform the function of carbon(C)capture due to receiving little human disturbance.This study aimed to evaluate the C capture potential of fallow weeds in rice(Oryza sativa L.)cropping systems.A six-region,two-year on-farm investigation and a three-year tillage experiment were conducted to estimate C capture in fallow weeds in rice cropping systems.The on-farm investigation showed that the average mean C capture by fallow weeds across six regions and two years reached 112 g m^(-2).The tillage experiment indicated that no-tillage practices increased C capture by fallow weeds by 80%on average as compared with conventional tillage.The results of this study not only contribute to an understanding of C capture potential of fallow weeds in rice cropping systems,but also provide a reference for including fallow weeds in the estimation of vegetative C sink.

Long-Term Impacts of Cover Crops, Chicken Litter, and Crop Rotations on Soil Health in No-Till Systems

Identification of management practices that can improve soil health is critical to improving the sustainability of soybean [Glycine max (L.) Merr.] production. The objective of this study was to examine the long-term effects of continuous soybean, corn-soybean, and soybean-cotton rotations with chicken litter and cover crops (hairy vetch, wheat, fallow) on soil health parameters, including nutrient accumulation and soil organic matter dynamics under a split plot design. The depth intervals of soil sampling were 0 - 15, 15 - 30, 30 - 60, and 60 - 90 cm. Chicken litter resulted in 62.1% and 32.8% higher water extractable organic soil N content than fallow and wheat, respectively, in the surface 0 - 15 cm of soil only. However, there was no significant difference in 1-day Solvita respiration, water extractable organic C, C/N ratio, health score, moisture, earthworm, organic matter, pH, or CEC of soil among fallow, hairy vetch, chicken litter, and wheat regardless of soil depth. Unexpectedly, annual application of chicken litter at 4.4 Mg ha−1 as an N source or growing a winter-season cover crop such as hairy vetch or wheat for continuous 16 years did not significantly increase soil organic matter or water extractable organic soil C. Annual application of chicken litter at 4.4 metric tons (Mg) ha–1 for 16 years increased soil nitrate-nitrogen (NO3−-N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn) contents by 92%, 400%, 134%, 20%, 43%, 206%, and 430% in 0 - 15 cm depth compared with their initial soil values, respectively, extracted with Haney H3A-2 (2 g L–1 lithium citrate + 0.6 g L–1 citric acid + 0.4 g L–1 malic acid + 0.4 g L–1 oxalic acid) solution. The increases enhanced soil supply of these nutrients to following crops, but also increased the risks of losing them to the environment. Hairy vetch caused higher H3A extracted soil manganese (Mn) content than fallow and chicken litter in 0 - 60 cm. There was no significant difference in 1-day Solvita respiration, water extractable organic C and N, health score, moisture, organic matter, pH, CEC, or population of earthworm of soil among continuous soybean, corn-soybean, and soybean-cotton in any soil depth. Another major finding of this study was that continuous soybean exerted no adverse effect on soil health relative to the commonly used corn (Zea mays L.)-soybean and soybean-cotton (Gossypium hirsutum L.) rotations under no-tillage after 16 years. To mitigate the risks of nutrient runoff and leaching from long-term chicken litter application, we recommend reducing litter application rates and integrating cover crops into crop rotations to enhance nutrient cycling and reduce environmental impacts.

Experimental Study on No-tillage Cultivation of Flowering Chinese Cabbage in Rice Winter Fallow Fields

The research made comparisons on no-tillage cultivation and ploughing cultivations of Flowering Chinese cabbage on one-season paddy fields and explored the effects of no-tillage cultivation of Flowering Chinese cabbage on survival rate, insect damages, production cost, yield and benefits of plants. The results indicated that no-tillage cultivation reduced the injured rate of Flowering Chinese cabbage by cutworms, and production cost, but crop yield and output value declined as well. Specifically, yield in the treatment as per no-tillage cultivation lowered by 10.3% and 11.9% compared with the treatments by machine-based ploughing and manual ploughing, and the production interests declined by 11.9% and 11.1%, accordingly.

Species diversity,population structure and regeneration of woody species in fallows and mature stands of tropical woodlands of southeast Angola

This study in the dry tropical woodlands of SE Angola in Cuando-Cubango Province assessed the diversity and composition of woody species in fallows compared to those in mature woodlands. We assessed the population structure of the most harvested woody species by calculating size class distribution and evaluated their regeneration potential based on the density of saplings. The vegetation was surveyed in 20 plots of 20 × 50 m(1000 m2). In each plot, we measured the diameter at breast height(DBH) of all woody species with DBH ≥ 5 cm. The saplings were counted, identified and recorded; 718 individuals, corresponding to 34 species in 32 genera and 15 families were recorded. The size class distribution of target woody species showed three different patterns in fallows and mature woodlands. In general,most of the smaller diameter classes had more individuals than the larger ones did, showing that the regeneration may take place. However, in some diameter classes, the absence of larger stems indicated selective logging of larger trees. Few saplings were recorded in the fallows or mature woodlands; fire frequency and intensity is probably the main obstacle for seed germination and seedling survival rates in the studied area.

Remediation Effects of Water Management and Lime Application on Seasonally-Fallowed Cd-Contaminated Paddy Fields

In the light of the national policy of fallow, this study was conducted to determine how the different water management and lime application would affect soil physical and chemical properties, rice yield and cadmium （Cd） content of rice in fallow season. The results showed that, compared with the arid fallow, the waterlogging fallow decreased the soil pH value whereas signifcantly increased the soil organic matter content and the cation exchange quantity, and reduced the soil effective cadmium content and the rice cadmium content whereas could increase the rice yield to a certain extent. In the fooded fallow or the dry fallow, the application of lime mainly depended on the alkali conditioning of lime and the antagonistic effect of Ca2＋, which could signifcantly reduce the cadmium content of rice, and its effect would increase linearly with the increase of lime dosage, whereas had no significant effect on soil organic matter content and cation exchange quantity. In order to establish a linear equation of lime dosage and related indexes under the condition of waterlogging fallow or dry fallow, calculations showed that each application of lime at 1 000 kg/hm2 or kg/hmss2 could improve soil pH value by 0.238 2 or 0.246 5units respectively, and reduce the effective Cd content to 0.007 5 mg/kg both in the arid fallow and the waterlogging fallow conditions. The lime theoretic application rate for the lowest Cd content of late rice in the arid fallow was 5 120 kg/hm2, and the minimum limit of the Cd content in rice was 0.124 2 mg/kg; and the lime theoretic application rate for the highest yield of late rice in the submerged water fallow was 4 636 kg/hm2, the minimum theoretic Cd content in rice is 0.100 7 mg/kg, and it could reduce the Cd content in rice under the condition of submerged fallow and decrease the dosage of lime.

Effects of improved fallow with Sesbania sesban on maize productivity and Striga hermonthica infestation in Western Kenya

Striga hermonthica is a major constraint to smallholder sub-sistence agriculture production in the sub-Saharan African region. Low soil fertility and overall environmental degradation has contributed to the build-up of the parasitic weed infestation. Improved cropping systems have to be introduced to address the interrelated problems of S. her-monthica and soil fertility decline. Thus, the effects of improved fallow with leguminous shrub Sesbania sesban on maize yields and levels of S. hermonthica infestation on farm land in the bimodal highlands of western Kenya were investigated. The experimental treatments were arranged in a phased entry, and randomized complete block scheme were six months Sesbania fallow, 18 months Sesbania fallow, six months natural fallow consisting of regrowth of natural vegetation without cultivation, 18 months natural fallow, continuous maize cropping without fertilizer application, and continuous maize cropping with P and N fertilization. Results show that Sesbania fallows significantly （p0.05） increase maize yield relative to continuous unfertilized maize. S. hermonthica plant populations decrease in continuous maize between the first season （mean = 428 000 ± 63 000 ha-1） and second season （mean=51 000 ± 15 000 ha-1）, presumably in response to good weed management. S. hermonthica seed populations in the soil decrease throughout the duration of the experi-ment in the continuous maize treatments. Short-duration Sesbania fal-lows can provide modest yield improvements relative to continuous unfertilized maize, but short-duration weedy fallows are ineffective. Continuous maize cultivation with good weed control may provide more effective S. hermonthica control than fallowing.

Modeling habitat suitability and utilization of the last surviving populations of fallow deer(Dama dama Linnaeus,1758)

DüzlerçamıWildlife Reserve Area(WRA)is the last natural habitat of fallow deer(Dama dama)in the world.Fallow deer is native to Turkey,however,its geographical range is currently confined to DüzlerçamıWRA,Antalya.To date,a detailed habitat investigation of fallow deer dis-tribution has not been conducted.This study is vital for the last surviving populations of fallow deer in Turkey.There-fore,we studied the habitat suitability and utilization of fal-low deer in the DüzlerçamıWRA.Vegetation and wildlife inventory was surveyed across a total of 304 sample areas between 2015 and 2017.Plant species were recorded accord-ing to the Braun-Blanquet method and wildlife surveys were based on footprints,feces,and other signs of fallow deer.Classification and regression tree techniques,as well as MAXENT,were used to model vegetation and fallow deer habitat.Topographic position index,terrain ruggedness index,roughness index,elevation,and bedrock formation were also calculated and included in the models.Based on our results,we drafted a habitat protection map for fallow deer.To ensure sustainability of habitats where populations of fallow deer are found in Turkey,we developed recommen-dations such as closuring human access of the 1st-degree Protection Area and reintroduction of the species to other potential habitats.

Research on Scientifically and Rationally Promoting the Fallow of Cultivated Land under the Strategy of Rural Revitalization

Implementing the rural revitalization strategy is an important decision-making arrangement made by the party s 19th National Congress,and is the general grasp of the work of"agriculture,rural areas and farmers"in the new era.In rural development,the issue of cultivated land is an important way to promote poverty alleviation in the vast rural areas and build a well-off society in an all-round way.In combination with the fact that the current quality of cultivated land resources in China is not high and the basic fertility has been continuously declining caused due to pollution,China must promote a scientific and rational system of arable land fallow to ensure the further development of agricultural modernization in China.In the process of researching the implementation of the arable land fallow system,the problems of land abandonment and"non-agriculturalization"after farmland fallow,the willingness of farmers to fallow and the subsidy for farmland fallow have been discovered.In response to the problems above,corresponding policy recommendations are put forward in order to better promote the process of arable land fallow and poverty alleviation in China.

Fractal Kinetics Parameters Regulating Carbon Decomposition Rate under Contrasting Soil Management Systems

Agricultural soils can sequester and release large amounts of carbon. Accessibility of soil carbon to microbial attacks depends on biological, chemical, and physical protection mechanisms such as organic matter composition and particle size, soil aggregation, and chemical protection through the silt-clayorganic matter complex. While soil and organic matter are fractal objects controlling exposure of reactive surfaces to the environment, soil aggregation and biomass production and quality are regulated by agricultural practices. Organic matter decomposition in soil is generally described by the classical first-order kinetics equations fitted to define distinct carbon pools. By comparison, fractal kinetics assigns a coefficient to adjust time-dependent decomposition rate of total soil carbon to protection mechanisms. Our objective was to relate fractal parameters of organic matter decomposition to soil management systems. Retrieving published data, the decomposition of organic matter was modeled in a silt loam soil maintained under pasture, annual cropping or bare fallow during 11 years. The classical first-order kinetics model returned quadratic relationships indicating that reactive carbon decreased with time. Fractal kinetics rectified the relationships successfully. Initial decomposition rate (k 1 at t = 1) was 7 × 10-4 for pasture, 1 × 10-4 for annual cropping, and 0.5 × 10-4 for bare-soil fallow. Fractal coefficients h were 0.71, 0.45, and 0.25 for pasture, annual cropping and fallow, respectively. Due to aggregation, physical protection against microbial attacks was highest under pasture management, leading to higher carbon sequestration despite higher biomass production and “priming” effects. Parameters k 1 and h proved to be useful indicators for soil quality classification integrating the opposite effects of labile carbon decomposition and carbon protection mechanisms that regulate the decomposition rate of organic matter with time as driven by soil management practices.

Comparison of Soil Quality Improvement under Different Fallow Types on Dystric Nitosols Derived from Sand Stone in South Western Nigeria

The project was carried out to determine the effects of different fallow types on soil derived from sand stone of low nutrient status in south western Nigeria. The different fallow types include Leu-caena, elephant grass, guinea grass and secondary forest. Cultivated farm land was used to serve as control for comparison of soil quality improvement. Soil samples were collected in four replicates on each land cover type and analyzed for major physical and chemical parameters. The results show little fertility improvement for base saturation with 1.42 cmol/kg in Leucaena, 1.99 cmol/kg in secondary forest, 1.60 cmol/kg in guinea grass and in Elephant grass. Leucaena resulted to better soil quality than secondary forest especially in surface properties though not significantly different. Elephant grass and guinea grass also resulted to better Nitrogen content. Nitrogen content recorded in Leucaena was high with 0.20% - 0.25%. Guinea grass and elephant grass resulted to better soil quality in terms of nitrogen content [0.20% - 0.25%] than cultivated and secondary forest [0.07% - 0.11%] due to their yearly incorporation in to the soil by ploughing. The values of phosphorus were higher in Leucaena though not significant [6.46 mg/kg]. Low soil properties improvement is attributed to nutrient exploitation in Leucaena and secondary forest after a long period of fallow [20 years] while, nitrogen enrichment in the grasses is attributed to yearly tillage. Over all low to medium soil variability indicates that the soils could be managed as a unit for crop production.

Nitrogen Recoveries and Yields Improvement in Cowpea sorghum and Fallow sorghum Rotations in West Africa Savannah

The effects of previous cowpea （Vignaunguiculata） and annual fallow on N recoveries, succeeding sorghum yields and soil properties were studied using a 5-year-old （1995-1999） field experiment at Kouar6 （11°59′ North, 0°19′ West and 850 m altitude） in Burkina Faso. A 3 4 factorial design in a split plot arrangement with three rotation treatments and four fertilizer treatments was used. Total N uptake by succeeding sorghum increased from 26 kg N ha~ in mono cropping of sorghum to 31 and 48 kg N ha~ when sorghum was rotated with fallow or cowpea respectively. Nitrogen derived from fertilizer increased from 10% in mono cropping of sorghum to 22% and 26% when sorghum was rotated with fallow or cowpea respectively. While fallow did not increase N derived from soil, cowpea doubled the quantity of N derived from soil （Ndfs）. Sorghum grain yields increased from 75% and 100% when sorghum was rotated with fallow or cowpea respectively. All rotations treatments decreased soil organic C and N but soil organic C was the highest in fallow-sorghum rotation. It was concluded that cowpea-sorghum rotation was more effective than fallow-sorghum rotation and five management options were suggested to improve traditional system productivity.

Fertility Reduction in Male Persian Fallow Deer (Dama dama mesopotamica): Inbreeding Detection and Morphometric Parameters Evaluation of Semen

Persian fallow deer (Dama dama mesopotamica) is only found in a few protected and refuges areas in the northwest, north, and southwest of Iran. The aims of this study were analysis of inbreeding and morphometric parameters of semen in male Persian fallow deer to investigate the cause of reduced fertility of this endangered species in Dasht-e-Naz National Refuge, Sari, Iran. The Persian fallow deer semen was collected by an electroejaculator from four adult bucks randomly during the breeding season and from five dehorned and horned deer’s in non-breeding season. Twelve blood samples were taken and mitochondrial DNA was extracted, a non-coding region called d-loop was amplified, sequenced and then were considered for genetic analysis. The Persian fallow deer’s normal and abnormal spermatozoa were similar to that of domestic ruminants but very smaller and difficult to observe at the primary observation. The post-mating season collected ejaculates contained abnormal spermatozoa, debris and secretion of accessory glands in horned bucks and accessory glands secretion free of any spermatozoa in dehorned or early velvet budding bucks. Microscopic evaluation in all four bucks during the mating season showed the mean concentration of 9 × 106 spermatozoa/ml. The mean ± standard deviation of age, testes length and testes width was 4.60 ± 1.52 years, 3.58 ± 0.32 and 1.86 ± 0.09 cm, respectively. The results identified 1120 loci in which 377 were polymorphic. In conclusion, reduced fertility of male Persian fallow deer may be caused by inbreeding of the protected herd in a limited area of Dasht-e-Naz National Refuge.

Extent of Reduction of the Fallow Period and Its Impact on Upland Rice Production in the Nongowa Chiefdom of Kenema District in Eastern Sierra Leone

Slash-and-burn agriculture is the common practice for upland rice intercropping system in Sierra Leone and it has been blamed for the loss of forest vegetation across the country. Shortening of the fallow period in the Eastern region of Sierra Leone has implications on agricultural food production and the persistence of the remaining tropical rainforest. This study was therefore undertaken to assess: 1) the extent of reduction of the fallow period in the Nongowa Chiefdom of Kenema District;2) the causes of reduction in the fallow period;3) farmers’ perception of the relevance of fallow period and the implications of reduction of fallow period on crop production. The study revealed a drastic reduction of the fallow period in the chiefdom with a mean of 3.8 years which falls far below the country mean fallow period of 8.8 years as estimated by FAO. Farmers pointed out that the reduction of the fallow period was as a result of land scarcity due to competing land uses such as large scale commercial agriculture, logging, mining, charcoal burning and expansion of settlements. Farmers agreed that a fallow period of at least 10 years is necessary for upland rice production. Farmers were aware of the impact of reduction of the fallow period on upland rice production and were able to estimate rice yields based on the age of the fallow. Also, farmers have attempted to adapt to the constraints posed by shorter fallow periods by selection of rice varieties to suit the length of the fallow periods.

Native Species Composition and Diversity of Valuable Woody Plants Regeneration during Fallow Period in Kamwatta, Moruca, Guyana

An intelligent method of shifting cultivation to regenerate vegetation after a long fallow period is critical information for restoration strategies. The literature review identified that the assessment of woody plant species on abandoned farmland has never been done before in Kamwatta, Moruca Region 1. In addition, more information should be available in indigenous communities and at the national level, including more documentation of the utilization of natural resources by the Warrau community. This study assessed the valuable woody plant species that grew during the fallow periods. Nine farmlands were randomly selected along a 100 m transect, each with varying fallow periods. In order to collect information on the age of farm abandonment, the researcher employed a mixed-methods approach. First, we found how long each farm had been fallow by administering a semi-structured questionnaire. Then, we conducted a flora survey to gain information on the variety and abundance of valuable plants using the age of farm abandonment as a dependent variable. The data analysis included the number of valuable woody trees with a diameter of >10 cm, seedlings and saplings with a diameter of <10 cm, the location of identified trees, and the uses of identified tree species. Microsoft Excel was used to code and analyze the questionnaire, while QGIS, Shannon’s Index of Diversity, and Simple Linear Regression were used to analyze the inventory data. The results showed that the respondents listed 38 valuable woody species, and 79% occurred in the studied area. The field verification revealed that the dominant family in the area was Mimosaceae. Species abundance increased with fallow up to 10 years before declining in the latter years. Plant diversity and abundance had a weak relationship with the age of abandoned farmlands for woody trees, while the seedlings and saplings showed no relationship.

Visual Analysis of Crop Rotation Fallow Patterns in Recent 5 Years Based on CiteSpace

Based on the"Web of Science Core Collection"(SCIE database),this article used the visualization software CiteSpace to visualize and analyze the crop rotation fallow patterns in the past five years.It analyzed the countries,institutions,keywords and hot topics of related literature to explore their research characteristics and development,and to provide reference for crop rotation fallow research and practice.The research shows that:1)developed countries are the main research force in the field of crop rotation and fallowing,and the connection between the research of each country and each institution is not close;2)research hotspots can be mainly summarized as:crop growth and yield,greenhouse gas emissions and soil health analysis,and the research in this field is constantly refined,combining macro and micro;3)In recent years,there is a big gap between China and foreign countries in the field of crop rotation and fallow research.It is necessary to strengthen the cooperation with research institutions in developed countries in Europe and the United States,and to carry out cross-regional and interdisciplinary research cooperation to improve the quality of papers and scientific research level.

耕地“三位一体”保护视角下中国省域休耕规模与空间布局

实施土地休耕是落实“藏粮于地”战略的关键,目前宏观尺度的全国休耕空间布局尚未确定,该研究探究了粮食安全约束下的全国范围内最大休耕规模以及中国省域休耕空间优化布局。以耕地数量、质量和生态“三位一体”保护为研究视角,该研究通过系统动力学、灰色预测模型等方法构建最大休耕规模预测模型,并结合“压力-状态-响应”模型构建休耕迫切度评价体系,依据评价结果分配各省休耕规模,从而得到中国省域休耕空间布局。结果表明:1)预计在90%、95%、100%的粮食自给率下,到2030年中国最大休耕规模分别为3237.310万、2678.970万和2120.640万hm^(2);2)省域之间的休耕迫切度水平存在差异,上海、内蒙古等地休耕迫切度较高,四川、广西等地休耕迫切度较低;3)在耕地三位一体保护的约束条件下,地区之间休耕规模差异较大,内蒙古、甘肃等地休耕规模较大,北京、上海等地休耕规模较小。该研究将数量、质量和生态多元目标融合进休耕空间分区研究,能够为未来休耕制度的全面建立以及精准落地提供思路与方法参考。

中国耕地种植制度遥感探测及其时空特征

[目的]耕地种植制度是农业生产方式的具体体现,其形成受自然资源要素与人类土地利用行为综合影响,反映了“人类-自然”的耦合关系。本研究旨在科学掌握全国耕地种植制度格局,为优化农业生产布局、提高农业生产能力、推动农业可持续性发展提供依据。[方法]结合遥感监测与空间决策树模型等手段,构建适合我国农情的跨年度种植制度探测方法体系,并开展空间格局分析。首先,通过辨析种植强度、复种指数等概念,从长期性、周期性、稳定性等方面,定义种植制度的内涵;其次,构建连续度、频度指标,并利用基于时序遥感的2001—2018年中国复种指数监测结果,结合时间滑动窗口方法,在像元尺度分别计算两个指标的具体值;最后,评估耕地的种植强度与种植制度特征的显著性,利用决策树方法确定种植制度类型,从区域差异、动态规律等方面分析不同区域种植制度的时空异质特征。[结果](1)面积上看,一年一熟所占面积最大,占53.52%,超过耕地总面积的一半;其次是一年两熟,占23.28%,季节性休耕(如两年三熟)与年度休耕分别占12.80%和6.94%。(2)空间上看,一年一熟、一年两熟、季节性休耕与年度休耕的集中分布区分别为东北地区、华北地区、长江以南地区与“镰刀弯”地区。(3)时间上看,动态稳定的种植制度从时间维度上揭示了静态复种指数背后的异质性,例如,2018年复种指数为1的区域,其中75.18%属于一年一熟、6.60%属于一年两熟、8.92%属于季节性休耕、8.02%属于年度休耕。[结论]本研究提出了一种结合时序遥感监测与空间决策树模型的跨年度分类体系,揭示了中国耕地种植制度分区聚集、种植强度南高北低的空间格局,直观展现了松嫩平原、“镰刀弯”等空间聚集区;分析了耕地复种与种植制度的时空差异特征,主要表现在种植制度与年度复种指数的空间不一致性,以及种植制度特有的周期性。研究结果可为合理提高耕地复种强度、推动实施“藏粮于地”战略提供案例支撑。