Upland Crop Fields Research Articles

Effect of Mixed Treatment of Urea Fertilizer and Zeolite on Nitrous Oxide and Ammonia Emission in Upland Soil

Ammonia loss from urea significantly hinders efficient use of urea in agriculture. The level of nitrous oxide (<TEX>$N_2O$</TEX>) a long-lived greenhouse gas in atmosphere has increased mainly due to anthropogenic source, especially application of nitrogen fertilizers. There are reports in the literature showing that the addition of zeolite to N sources can improve the nitrogen use efficiency. This study was conducted to evaluate nitrous oxide (<TEX>$N_2O$</TEX>) and ammonia (<TEX>$NH_3$</TEX>) emission by mixed treatment of urea and zeolite in upland crop field. Urea fertilizer and zeolite were applied at different rates to study their effect on <TEX>$N_2O$</TEX> emission during red pepper cultivation in upland soils. The <TEX>$N_2O$</TEX> gas was collected by static closed chamber method and measured by gas chromatography. Ammonia concentration was analyzed by closed-dynamic air flow system method. The total <TEX>$N_2O$</TEX> flux increased in proportion to the level of N application. Emission of <TEX>$N_2O$</TEX> from the field increased from the plots applied with urea-zeolite mixture compared to urea alone. But urea-zeolite mixture treatment reduced about 30% of <TEX>$NH_3$</TEX>-N volatilization amounts. These results showed that the application of urea and zeolite mixture had a positive influence on reduction of <TEX>$NH_3$</TEX> volatilization, but led to the increase in <TEX>$N_2O$</TEX> emission in upland soils.

Assessment on the rates and potentials of soil organic carbon sequestration in agricultural lands in Japan using a process-based model and spatially explicit land-use change inventories – Part 1: Historical trend and validation based on nation-wide soil monitoring

Abstract. In order to estimate a country-scale soil organic carbon (SOC) stock change in agricultural lands in Japan, while taking into account the effect of land-use changes, climate, different agricultural activities and the nature of soils, a spatially explicit model simulation system was developed using Rothamsted Carbon Model (RothC) with an integration of spatial and temporal inventories. Simulation was run from 1970 to 2008 with historical inventories. Simulated SOC stock was compared with observations in a nation-wide stationary monitoring program conducted during 1979–1998. Historical land-use change, characterized by a large decline in the area of paddy fields as well as a small but continuous decline in the area of orchards, occurred along with a relatively large increase in upland crop fields, unmanaged grasslands, and settlements (i.e. conversion of agricultural fields due to urbanization or abandoning). Results of the simulation on SOC stock change under varying land-use change indicated that land-use conversion from agricultural fields to settlements or other lands, as well as that from paddy fields to croplands have likely been an increasing source of CO2 emission, due to the reduction of organic carbon input to soils and the enhancement of SOC decomposition through transition of soil environment from anaerobic to aerobic conditions. The area-weighted mean concentrations of the simulated SOC stocks calculated for major soil groups under paddy fields and upland crop fields were comparable to those observed in the monitoring. Whereas in orchards, the simulated SOC stocks were underestimated. As the results of simulation indicated that SOC stock change under managed grasslands and settlements has been likely a major sink and source of CO2 emission at country-scale, respectively, validation of SOC stock change under these land-use types, which could not have been accomplished due to limited availability or a lack of measurement, remains a forthcoming challenge.

Soil-to-crop transfer factors of tellurium

Stable tellurium (Te) concentrations in 148 sets of agricultural soil and associated crop samples were measured in this study to obtain soil-to-crop transfer factor (TF) of Te. We used a recently developed simple method that applies digestion of samples with aqua regia and sector field inductively coupled plasma mass spectrometry to measure low Te levels in these samples. Geometric mean (GM) concentrations of Te in soil and crops were 75μgkg−1-dry (range: 15–850μgkg−1-dry) and 1.8μgkg−1-dry (range: 0.1–120μgkg−1-dry), respectively; the Te concentration range was significantly wider in crops than in soil. Using these data, we calculated TFs and obtained their range from 1.3×10−3 to 1.1×10−1. The GM of TF for upland field crops was calculated to be 2.0×10−2 and for brown rice was 3.1×10−2; all crop types had the similar GMs of their TF values. Data comparison for TF of Te was carried out with six elements, which are present in anionic forms in soil environment like Te is, i.e. P, Br, As, Se, Mo, and I. TFs of Te and I showed the highest correlation factor for upland field crops by t-test (r=0.577, p<0.001), but no correlation was found for brown rice. We considered it likely that different water management practices in upland fields and paddy fields affected the Te transfer from soil to crops.

Physico-chemical variables and their effect on the growth performance of some major carps in some ponds of a matsaya gram (Fish village) in Natore

An experiment was carried out to asses the physico-chemical characteristics, water quality and fish growth suffered by pollution hazards created by unethical use of agrochemical in few ponds in a matsaya gram (fish fillage) in northern part of Bangladesh. The range of free CO2, DO, HCO3, CO3 and pH were 2-30mg/l, 3.14-11.86 mg/l, 86.31-143.84mg/l, 0 -50mg/l and 8.5-9.5 respectively. The BOD of the studied ponds found quite less than optimum level. The study of relationship between fish growth and the soil characters showed negative impact. It revealed that due to minimum rainfall the ponds were not washed out that could decrease the rate of pollution created from the nearest house and residual chemicals, those used in upland crop field beside it. But the ponds are still suitable for fish culture and should keep them at least in present position for good crop.DOI: http://dx.doi.org/10.3329/ujzru.v31i0.15401Univ. j. zool. Rajshahi Univ. Vol. 31, 2012 pp. 55-58

Design of an agent-based model to examine population–environment interactions in Nang Rong District, Thailand

The design of an agent-based model (ABM) is described that integrates Social and Land Use Modules to examine population–environment interactions in a former agricultural frontier in Northeastern Thailand. The ABM is used to assess household income and wealth derived from agricultural production of lowland, rain-fed paddy rice and upland field crops in Nang Rong District as well as remittances returned to the household from family migrants who are engaged in off-farm employment in urban destinations. The ABM is supported by a longitudinal social survey of nearly 10,000 households, a deep satellite image time-series of land use change trajectories, multi-thematic social and ecological data organized within a GIS, and a suite of software modules that integrate data derived from an agricultural cropping system model (DSSAT – Decision Support for Agrotechnology Transfer) and a land suitability model (MAXENT – Maximum Entropy), in addition to multi-dimensional demographic survey data of individuals and households.The primary modules of the ABM are the Initialization Module, Migration Module, Assets Module, Land Suitability Module, Crop Yield Module, Fertilizer Module, and the Land Use Change Decision Module. The architecture of the ABM is described relative to module function and connectivity through uni-directional or bi-directional links. In general, the Social Modules simulate changes in human population and social networks, as well as changes in population migration and household assets, whereas the Land Use Modules simulate changes in land use types, land suitability, and crop yields. We emphasize the description of the Land Use Modules – the algorithms and interactions between the modules are described relative to the project goals of assessing household income and wealth relative to shifts in land use patterns, household demographics, population migration, social networks, and agricultural activities that collectively occur within a marginalized environment that is subjected to a suite of endogenous and exogenous dynamics.

녹비작물과 바이오숯의 고추 재배지 아산화질소 배출량 저감 효과

농업 부문에서 온실가스 배출량을 줄이기 위하여 녹비작물인 헤어리베치와 바이오숯을 이용하였을 때 밭작물 재배지에서 아산화질소 배출량 저감 효과를 평가하였다. 질소 시용량은 고추의 표준 시비량인 <TEX>$190kg\;ha^{-1}$</TEX>이었으며, 주 2회 시료를 채취하여 GC/ECD로 아산화질소를 분석하였다. 대조구인 질소질 비료(요소) 처리구의 아산화질소 배출량은 <TEX>$1.14kg\;N_2O-N\;ha^{-1}$</TEX>이었으며, 헤어리베치와 바이오숯+질소질 비료 처리구의 아산화질소 배출량은 각각 <TEX>$0.61kg\;N_2O-N\;ha^{-1}$</TEX>과 <TEX>$0.86kg\;N_2O-N\;ha^{-1}$</TEX>로 온실가스 배출을 각각 46.5%와 24.6% 줄였다. Atmospheric nitrous oxide (<TEX>$N_2O$</TEX>) level has been increasing at a rate of 0.2~0.3% per year. The rise in <TEX>$N_2O$</TEX> concentration in atmosphere was mainly due to an increased application of nitrogen fertilizers. The objective of the study was to assess the effect of green manure crop and biochar on <TEX>$N_2O$</TEX> emissions from upland crop field. The green manure crop used in the study was hairy vetch and the cultivated crop was red pepper (Capsicum annuum L.). Nitrogen was applied at a rate of <TEX>$190kg\;ha^{-1}$</TEX>, standard N fertilization rate for red pepper. Emissions of <TEX>$N_2O$</TEX> from the field were reduced from the plots applied with hairy vetch and biochar by 46.5% and 24.6%, respectively, compared with nitrogen fertilizer treated plots with <TEX>$N_2O$</TEX> emission of <TEX>$1.14kg\;N_2O-N\;ha^{-1}$</TEX>. The results from the study imply that green manure crop and biochar can be utilized to reduce greenhouse gas emission from the upland crop field.

30년 콩-옥수수 윤작 및 경운처리 장기시험 포장의 토양 온실가스 발생

1. 30년 장기 연용구의 연작 대비 윤작에 의한 옥수수 및 콩의 수량증대는 옥수수보다 콩이 더 컸으며, 연작시 무경운에 따라 수량이 감소되었던 옥수수는 윤작에 의해 수량이 많이 회복되었다. 콩은 연 윤작구 모두 무경운에서도 수량이 감소하지 않았다. 2. 윤작구의 작물재배기간의 이산화탄소 누적발생량은 재배작물 및 처리간 차이가 없었으며, 메탄은 콩의 재배시 plow 경운구에서 생육초기에 증가하였다. 3. 아산화질소의 발생은 옥수수 생육초기 질소시비 후에 질소비료의 무기화 과정에서 발생량이 증가하였는데, 경운방법에 따라 차이가 뚜렷하여 chisel 경운에서 가장 높았고, 무경운에서 가장 낮았다. 4. 콩-옥수수 윤작체계에서 plow 및 chisel 경운에 비해 무경운(no-tillage)의 채택에 따라 작물의 수량 감소없이 콩 재배 시 메탄 <TEX>$0.7kg\;C\;ha^{-1}$</TEX> 및 옥수수 재배 시 아산화질소 <TEX>$2{\sim}4kg\;N\;ha^{-1}$</TEX> 발생량을 감소시킬 수 있었다. Reduction of greenhouse gas (GHG) emissions from upland crop field as well as paddy field is being required, but little information on GHG emissions according to cultivation practices in upland field is available. Soil GHG emissions during the growing season were investigated in the field of three decades rotation and tillage treatments which were consisted of plow, chiesl tillage and no tillage in west central Indiana, USA in 2006. Seasonal cumulative <TEX>$CO_2$</TEX> emissions were not different among treatments. <TEX>$CH_4$</TEX> emission increased a little in plow tillage during early soybean growing season. Most of <TEX>$N_2O$</TEX> emission occurred during early corn growing season after N-fertilizer application from mid June to mid July, and was significantly affected by tillage practices in which seasonal cumulative <TEX>$N_2O$</TEX> emission was significantly higher under chisel tillage. <TEX>$N_2O$</TEX> emission under no-tillage was lower about 64% and 39% than that under chisel tillage and plow tillage, respectively. No-tillage practice with rotation of corn and soybean seems to be promising in point of less GHG emission and less labor for cultivation without grain yield reduction.

Germination of Fresh Horse Purslane (Trianthema portulacastrum) Seeds in Response to Different Environmental Factors

Horse purslane, a C4 species, is a branched, prostrate, and annual weed of upland field crops throughout the tropics. Experiments were conducted to determine the influence of various environmental factors on seed germination and seedling emergence of two populations of horse purslane. Seeds were collected from rice fields of the International Rice Research Institute (the IR population) and from sorghum fields of the University of the Philippines (the UP population); the two sites were 5 km apart in Los Baños, Philippines. Germination response of both populations was greater at 30/20 C and35/25 C day/night temperatures than they were at 25/15 C alternating day/night temperatures. Germination of both populations was greater in the light/dark regime than in darkness. In dark, depending on the temperature, seed germination of the UP population ranged from 37 to 62%, whereas seed germination of the IR population was &lt; 20%. Exposure to 5 min at 117 and 119 C for the IR and UP populations, respectively, reduced germination to 50% of maximum germination. Osmotic potential of −0.26 MPa inhibited germination to 50% of the maximum for the UP population, whereas the corresponding value for the IR population was −0.37 MPa. Seeds placed on or near the soil surface had maximum emergence, and emergence declined with increase in seed burial depth. Seedling emergence of the UP and IR populations was 74% and 13%, respectively, for seeds placed on the soil surface. For both populations, no seedlings emerged from a soil burial depth of 6 cm or more. Germination and emergence responses to light and seed burial depth differed between the two populations of horse purslane. Residues on the soil surface of up to 6 Mg ha−1 did not influence seedling emergence of either populations. Knowledge gained in this study could contribute to developing components of integrated weed management strategies for horse purslane.

Assessing the application of a geographic presence-only model for land suitability mapping

Recent advances in ecological modeling have focused on novel methods for characterizing the environment that use presence-only data and machine-learning algorithms to predict the likelihood of species occurrence. These novel methods may have great potential for land suitability applications in the developing world where detailed land cover information is often unavailable or incomplete. This paper assesses the adaptation and application of the presence-only geographic species distribution model, MaxEnt, for agricultural crop suitability mapping in a rural Thailand where lowland paddy rice and upland field crops predominant. To assess this modeling approach, three independent crop presence datasets were used including a social-demographic survey of farm households, a remote sensing classification of land use/land cover, and ground control points, used for geodetic and thematic reference that vary in their geographic distribution and sample size. Disparate environmental data were integrated to characterize environmental settings across Nang Rong District, a region of approximately 1300 sq. km in size. Results indicate that the MaxEnt model is capable of modeling crop suitability for upland and lowland crops, including rice varieties, although model results varied between datasets due to the high sensitivity of the model to the distribution of observed crop locations in geographic and environmental space. Accuracy assessments indicate that model outcomes were influenced by the sample size and the distribution of sample points in geographic and environmental space. The need for further research into accuracy assessments of presence-only models lacking true absence data is discussed. We conclude that the MaxEnt model can provide good estimates of crop suitability, but many areas need to be carefully scrutinized including geographic distribution of input data and assessment methods to ensure realistic modeling results.

Soil purple phototrophic bacterial diversity under double cropping (rice-wheat) with free-air CO2 enrichment (FACE)

Soil purple phototrophic bacterial (PPB) communities and their responses to elevated atmospheric carbon dioxide (CO 2 ) concentration and nitrogen (N) fertilizer were investigated under a rotation of paddy rice (Oryza sativa L.) and winter wheat (Triticum aestivum L. cv. Yangmai 14) cultivation in a FACE (free-air CO 2 enrichment) system. Community structures and abundances of PPB were determined by denaturing gradient gel electrophoresis (DGGE) and real-time quantitative PCR respectively, targeting the pufM gene, which encodes a protein in the light reaction centre of PPB. Soil PPB communities were more diverse and larger under rice than under wheat cultivation, which may be attributed to the flooding of the paddy field and soil moisture changes. Elevated atmospheric CO 2 concentration significantly increased the abundance and biodiversity of PPB in soils under rice cultivation, while N fertilizer application rate had less effect on the abundance and diversity. Phylogenetic analysis showed that two common dominant DGGE bands belonged to Bradyrhizobium- and Rhodopseudomonas palustris-like PPB in both rice and wheat soils. The results demonstrated a significant shift in soil PPB communities during the rice-wheat rotation, and a strong positive response of PPB communities to an elevated atmospheric CO 2 concentration. Our results also indicated that a diverse and abundant soil PPB community could occur in upland crop fields as well as in aquatic environments and paddy-rice fields. These findings extend our understanding of the ecological significance of PPB in terrestrial soil environments and their responses to future climate change.

Optimization model for cropping-plan placement in paddy fields considering agricultural profit and nitrogen load management in Japan

An optimization model for cropping-plan placement on field plots is presented for supporting decision-making on agricultural management by a farming organization. The mixed 0–1 programming technique is employed to select the next planting crop at each field plot in a holistic manner. Reduction of total nitrogen discharged from field plots to the downstream end of the drainage canals is expressed as an objective function of the model to balance an achievement of economic goal and environmental conservation. Some Japanese governmental policies on regulating rice cropping areas and on promoting production of particular upland field crops can be formulated in the model. A computational example of cropping-plan placement on field plots managed under integrated policies is given by operating the optimization model with various weights associated with the objectives. The procured trade-off curve and corresponding patterns of cropping-plan could be useful in the decision-making by the farming organization.

A refined hydro-environmental watershed model with field-plot-scale resolution

A distributed hydro-environmental model is developed that achieves detailed analysis of the movement of water at a field-plot-scale resolution in a mesoscale watershed including lowland areas where, especially for agricultures, it is an essential need to get rid of redundant groundwater by drainage facilities such as rivers, canals and/or underdrains. For this, the problem geometry is meshed with unstructured cells of triangular shape. Profile of a column cell is zoned into two: surface zone and groundwater zone in which water movement is represented by combined tank and soil moisture sub-models, and well-defined two-dimensional unconfined shallow groundwater flow sub-model, respectively. The top-two sub-models serve to evaluate evapotranspiration, infiltration, soil water content, lateral surface water flow, and vertical percolation. The vertical percolation so evaluated is given as longitudinal recharge to the bottom sub-model for computing groundwater flow. Surface water–groundwater interactions through beds and stream-banks of perennial and ephemeral canals are considered by treating the canal courses as internal boundaries in the groundwater flow model. The finite volume method (FVM) that allows of unstructured mesh and produces conservative solutions is employed for groundwater flow computation. The model developed is applied to an actual watershed which includes a low-lying paddy area to quantify the hydrological impact of land-use management practices over a period of 29 years in which the farmland consolidation project was implemented and part of the paddy fields were converted to upland crop fields and housing lands. From the results obtained, it is concluded that the model presently developed lends itself to water—as well as land-use management practices.

Fuzzy optimization model for integrated management of total nitrogen loads from distributed point and nonpoint sources in watershed

A fuzzy optimization model is developed to allocate allowable total nitrogen (T-N) loads to distributed nonpoint sources (NPSs) and point sources (PSs) in a watershed for river water quality management using the linear programing technique. The watershed is divided into uniform grid cells on which T-N loads issuing from NPSs such as paddy fields, upland crop fields and cities are controlled. A geographic information system integrated with the digital elevation model facilitates computation of route lengths of surface and subsurface flows from cells to a river running through the watershed. The T-N loads discharged from their sources are assumed to decay, subject to distance-related first-order kinetics. As management goals, maximizations of total allowable NPS loads, total allowable PS loads and total yield of rice are considered from environmental and economic viewpoints. A prime constraint is an effluent limitation standard for the aggregate amount of loads that arrive at the downstream end of the river. The fuzzy sets theory helps appropriately describe vague attitudes of decision-makers (i.e., stakeholders and management authorities) in terms of constraints and conflicting goals. An application of the fuzzy optimization model, developed as an improvement over our last nonfuzzy model, to a real watershed in Shiga prefecture, Japan, demonstrates that the fuzzy model embodies our last model, and is capable of creating management alternatives for T-N load allocation in a more practical and flexible manner.

A distributed hydro-environmental watershed model with three-zoned cell profiling

A cell-based distributed watershed model is developed which enables us to simulate the hydrological and hydraulic aspects of the watershed in a refined fashion. With three-zoned cell profiling, the model is composed of three sub-models; tank model for a surface water zone, soil moisture model for a surface soil zone, and unconfined shallow groundwater flow model for a subsurface zone. Inclusion of the soil moisture sub-model modified to reroute the infiltration, routed from the tank sub-model, into the return flow and the groundwater recharge features the model. The groundwater flow sub-model, numerically approximated by use of the finite volume method and the implicit time-marching scheme, considers a network of on-farm drainage canals as internal boundaries, which is an essential need for modeling the watershed including farmlands. Cascade-linking of the three sub-models in a cell and assembling of all the cells over the entire watershed domain provides the global equations system to be solved. Applicability of the model is demonstrated with its practical application to a real watershed in that paddy and upland crop fields take great part of the land-use practice. It is then indicated in a quantified manner that rice farming significantly contribute as a major groundwater recharger in an irrigation period to fostering and conservation of regional water resources. Along with appropriately profiling a cell, the model is so versatile and tough that it can be applied without difficulty to a watershed of diverse terrains and land-uses and the computations can stably be carried out. It is thus concluded that the model presently developed could be a powerful “watershed simulator” to investigate and assess the time-varying hydro-environmental properties of a watershed while separating and integrating the hydrological and hydraulic components of particular importance.

沖縄県の畑作物，果樹，雑草等における植物寄生性線虫相

沖縄県の畑作物，果樹，雑草等における植物寄生性線虫相

Nitrous oxide fluxes from upland soils in central Hokkaido, Japan

Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November), for three years, in a total of 11 upland crop fields in central Hokkaido, Japan. The annual mean N2O fluxes ranged from 2.95 to 164.17 microgN/(m2 x h), with the lowest observed in a grassland and the highest in an onion field. The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall events around harvesting in autumn. No clear common factor regulating instantaneous N2O fluxes was found at any of the study sites. Instead, instantaneous N2O fluxes at different sites were affected by different soil variables. The cumulative N2O emissions during the study period within each year varied from 0.15 to 7.05 kgN/hm2 for different sites, which accounted for 0.33% to 5.09% of the applied fertilizer N. No obvious relationship was observed between cumulative N2O emission and applied fertilizer N rate (P > 0.4). However, the cumulative N2O emission was significantly correlated with gross mineralized N as estimated by CO2 emissions from bare soils divided by C/N ratios of each soil, and with soil mineral N pool (i.e., the sum of gross mineralized N and fertilizer N) (P < 0.001).

Soil-to-Plant Transfer Factors of Stable Elements and Naturally Occurring Radionuclides (1) Upland Field Crops Collected in Japan

In long-term dose assessment models for radioactive waste disposal, an important exposure pathway to humans is via ingestion of contaminated foods. In order to obtain soil-to-plant transfer factors (TFs) of radionuclides under equilibrium conditions, naturally existing elements were measured as analogues of radionuclides. Crops grown in upland fields and associated soil samples were collected from 62 sampling sites throughout Japan. The total concentrations of 52 elements in the crops and 54 elements in the soil samples were measured. The TFs of 40 elements (Li, Na, Mg, Al, Si, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Pb, Th and U) were calculated on a dry weight basis. Among all the TF data, K showed the highest TF with a geometric mean (GM) of 2.1, followed by P. The GMs of TFs for rare earth elements, Th and U were on the order of 10−4. Most of the TF-GMs for green vegetables were higher than GMs of all crops for the elements. The obtained TFs of some elements for green vegetables and potatoes were compared with those in the technical report series-364 (TRS-364) compiled by IAEA in 1994. The TF-GMs were usually lower than the best estimates (expected values) listed in TRS-364; however, the GMs of TF for La and TF for Th observed for potatoes were slightly higher than the expected values.

Distribution of Arbuscular Mycorrhizal Fungi in Upland Field Soil of Japan 1. Relationship Between Spore Density and The Soilenvironmental Factor

To Quantify The Effects of Arbuscular Mycorrhizal Fungi (Am Fungi) On The Growth of Upland Field Crops Cultivated in Japan, We Analyzed Soil Samples From 124 Sites in 18 Japanese Prefectures For Available P Content, Ph and Am Fungal Spore Density. The Am Fungal Spore Density in The 124 Soil Samples Was 1.7 Per G Dw On The Average, and Lower Than 1.0 Per G Dry Soil (Dw) in About Half of The Soil Samples. The Maximum Spore Density Was 20.6 Spores Per G Dw. The Density of Am Fungal Spore Did Not Vary Significantly With The Sampling Site and The Kind of Cultivated Crop in The Sampling Field. The Ph of The Soil With A High Spore Density Ranged From 6 To 8, and in The Soil Samples With A Ph Lower Than 6 and Higher Than 8, TheSpore Density Was Lower Than 5 Spores Per G Dw. Thus, in The Acid Or Alkaline Soil, The Sporogenesis of Am Fungi Is Suppressed. Because Available P Content Was Consistently Low in The Soil Samples With A High Spore Density, P Content Was Considered To Correlate With The Am Fungal Spore Density. Therefore, Crop Cultivation With Limited P Fertilizer Application and Reduced Available P Content May Be Important To increase Am Fungal Spore Density in Upland Field Soil.

Coordinating Irrigation Practice in a Mixed Area of Upland Crop Fields and Greenhouses

Coordinating Irrigation Practice in a Mixed Area of Upland Crop Fields and Greenhouses

Spatial simulation modelling of land use/land cover change scenarios in northeastern Thailand: a cellular automata approach

The cultivation of upland field crops, primarily cassava and sugar cane, in Nang Rong district, northeast Thailand, beginning in the mid- to late 1960s, has helped transform a once forest-dominated landscape to one dominated by agriculture. Today, paddy rice is cultivated throughout the lowlands, field crops and a fragmented forest matrix comprise the uplands, and fruit trees, rubber plantations, and vegetable gardens are among the crops dispersed around nuclear villages. Distributed along a topographic terrace system, upland and lowland crops are cultivated relative to environmental and economic opportunities and geographic access, although crops grown in marginal settings may not be sustainable. Relying upon a remote sensing image time-series, a longitudinal social survey, and GIS coverages, a cellular automata (CA) model is described that is used to characterize land use and land cover (LULC) change patterns through specified initial conditions, neighbourhood associations, and transition or growth rules. Results of four scenarios or experiments are described that perturb the base LULC change model of cassava, forest, and rice by imposing production quotas in the cultivation of cassava. Derived for the period 1972–2001, CA model results for the scenarios are compared to a time-series of Landsat satellite classifications of LULC using images of simulation runs and plots that describe trends in the composition and spatial organisation of cassava, forest, and rice for each scenario. Results are interpreted within a population-environment context in which people, place, and environment are integrated in complex ways. The demise of forest at the expense of expanded lowland paddy rice and upland field crops is a central story of the region. Quotas on the production of cassava alter the trajectories of forest change and result in more consolidated forest stands over the period of the simulations. Cassava consolidation and in-filling in the extensive uplands of the southwest portion of Nang Rong district is a persistent outcome of the simulations for the various scenarios tested.