Upland Crop Production Research Articles

Innovation in Two Contrasting Value Chains: Constraints and Opportunities for Adopting Upland Crop Production in the Vietnamese Mekong Delta

Innovation in Two Contrasting Value Chains: Constraints and Opportunities for Adopting Upland Crop Production in the Vietnamese Mekong Delta

Projected changes in field workability of agricultural machinery operations for upland crop production with +4 K warming in Hokkaido, Japan

Projected changes in field workability of agricultural machinery operations for upland crop production with +4 K warming in Hokkaido, Japan

Development of Low-cost Soil Moisture Monitoring System for Efficient Irrigation Water Management of Upland Crops

With the advancement of information and communication technology, various types of soil moisture sensors have been developed. Coupled with data loggers, these sensors could prove useful in monitoring soil moisture in upland crop production areas which in turn could be used for efficient irrigation water management. However, most of these sensors are costly and unaffordable to most farmers in developing countries. Hence, a low-cost soil moisture monitoring system intended to facilitate irrigation water management in upland crop production systems was developed in this study. The device was built with a capacitive soil moisture sensor, an ESP8266 Wi-Fi mini board, and a datalogging shield with RTC. Soil moisture measurements are transmitted via ESP-NOW to a server which also uses an ESP8266 Wi-Fi mini board. The low-cost soil moisture monitoring system was evaluated based on its measurement of volumetric water content and transmission of data via ESP-NOW. The performance of the capacitive soil moisture sensor was compared with the ICT International MP306 soil moisture sensor. Statistical analyses showed that volumetric water contents measured by the capacitive soil moisture sensor are comparable to those of the MP306 soil moisture sensor, thus conceived as a low-cost alternative to the high-end sensor. Moreover, test results on the range of ESP-NOW showed that data can be successfully transmitted over long distances. With regards to this, the low-cost soil moisture monitoring system may be integrated with other technologies to enable irrigation scheduling and automation for efficient irrigation water management in upland crop production systems.

Development of a real-time wireless sensor network-based information system for efficient irrigation of upland and lowland crop production systems

This study developed a real-time web-and WSN-based information system for efficient irrigation water management and automation of drip-irrigated upland crop and intermittently-irrigated lowland crop production systems. The web-based system uses Flutter and DART to accommodate multiple end user platforms, while the WSN-based system uses state-of-the-art hardware and sensors for real-time monitoring of soil moisture, water level and weather conditions. The sensors are wirelessly connected in a low-power mesh network that sends data to a central server. The sensor readings are uploaded to the web application via MQTT, which generates charts and graphs for data analysis. The sensor readings compared well with measurements from conventional instruments. The system in this study provides a sustainable solution for improving irrigation efficiencies under both upland and lowland crop production systems, in minimizing water losses and in improving the overall agricultural crop productivity.

Hydraulic Performance Evaluation of Low-Cost Gravity-Fed Drip Irrigation Systems Under Constant Head Conditions

The use of drip irrigation for upland crop production has gained popularity in developing countries due to its relatively high water-use efficiency. To maximize the efficiency of this irrigation method, it is important to evaluate its hydraulic performance in terms of emitter discharge and water distribution uniformity under various operating heads. In this study, the hydraulic performance of two locally available low-cost drip irrigation kits -referred to in this study as Drip Kit A and Drip Kit B - was assessed and compared under constant head conditions. Both drip kits are composed of a 1000-L intermediate bulk container (IBC) tank, 10-m submain line, 20-m lateral lines spaced 0.75 m apart, and cascade labyrinth emitters spaced 0.30 m apart along the laterals. Operating heads of 2.5, 3.5, 4.0, 4.5, 5.0, 5.5 m were used and maintained throughout the trials with the use of an overflowing tank. The submain and lateral lines were levelled (0% slope). Sampling of discharge rates was done for one-third of the total number of emitters for each of the tests performed. Results showed that the overall system emitter discharge rate generally increases with increasing operating head. Moreover, emitters farther from the submain line generated relatively lower discharge rates than those closer to it. Analysis of the experimental data showed that the Christiansen’s coefficient of uniformity (CU), emission uniformity (EU), and coefficient of variation (CV) ranged from 97.5 to 98.5, 95.9 to 97.7, and 0.02 to 0.04 for the drip systems tested. Further statistical analysis also showed that varying the operating heads does not have a statistically significant effect (α=5%) on the CU, EU, and CV of the system. Based on the results, Drip Kit B performed better than Drip Kit A in terms of water distribution uniformity. However, the latter could generate higher emitter discharge rates than the former. For both drip kits, an operating head of 2.5-m is recommendable for a 200 m2 plot, from the practical standpoint. This study has generated important empirical data that could serve as a basis for maximizing the performance efficiency of locally available drip irrigation systems for a more efficient irrigation water management.

Development of mobile application for wireless sensor networks for efficient irrigation water management

The evolution of smart phones has necessitated the development of mobile applications designed to perform a wide variety of functions. In the field of agriculture, mobile applications are currently used to monitor environmental parameters such as ambient temperature, humidity, soil moisture, water level, among others. A mobile application intended to monitor irrigation-related parameters and to control solenoid valves for irrigation automation was developed in this study. The mobile application was written using Flutter software development kit, and the Dart programming language. The mobile application communicates with the cloud server using a REST API written in JavaScript. The data acquired from the cloud server are presented as the current sensor reading and graphs. On the other hand, the mobile application controls the solenoid valves by sending designated bytes of data to the cloud server. The mobile application developed in this study was designed to be integrated with both low-cost sensors and the Smartmesh IP sensors to enable real-time monitoring and data visualization, and facilitate irrigation scheduling and manual irrigation control. The mobile application developed in this study may be used for efficient irrigation water management of upland crop production systems and for agricultural modernization in the Philippines and other developing countries.

Genetic regulation of root traits for soil flooding tolerance in genus Zea.

Flooding stress caused by excessive precipitation and poor drainage threatens upland crop production and food sustainability, so new upland crop cultivars are needed with greater tolerance to soil flooding (waterlogging). So far, however, there have been no reports of highly flooding-tolerant upland crop cultivars, including maize, because of the lack of flooding-tolerant germplasm and the presence of a large number of traits affecting flooding tolerance. To achieve the goal of breeding flooding-tolerant maize cultivars by overcoming these difficulties, we chose highly flooding-tolerant teosinte germplasm. These flooding-tolerance-related traits were separately assessed by establishing a method for the accurate evaluation of each one, followed by performing quantitative trait locus (QTL) analyses for each trait using maize × teosinte mapping populations, developing introgression lines (ILs) or near-isogenic lines (NILs) containing QTLs and pyramiding useful traits. We have identified QTLs for flooding-tolerance-related root traits, including the capacity to form aerenchyma, formation of radial oxygen loss barriers, tolerance to flooded reducing soil conditions, flooding-induced adventitious root formation and shallow root angle. In addition, we have developed several ILs and NILs with flooding-tolerance-related QTLs and are currently developing pyramided lines. These lines should be valuable for practical maize breeding programs focused on flooding tolerance.

Soil Water Profiles, and Growth and Yield of Waxy Corn as Affected by Different Tillage in Upland Converted from Paddy Field

In Korea, rice consumption per capita has steadily been reducing, and hence the harvested area of paddy rice decreased by 18% from 892,074 ha in 2010 to 729,814 ha in 2019 during last decade, leading to the potential to stimulate upland crop production in converted-upland from paddy field. Here, we examined how tillage practice, rotary (RT) in 12cm depth vs. rotary combined with deep tillage (RTDT) in 25cm depth, would affect vertical profiles (0 to 40 cm at 10 cm interval) of soil water and, growth and yield parameters of waxy corn (Zeay Mays L., ceratina, cv. Ilmichal) grown as sequential cropping of barely in upland field converted from paddy field. With rainfall and sprinkler irrigation, vertical profiles of soil water were varied greatly (20 cm > 40 cm > 30 cm > 10 cm) over whole season in RTDT plot, but not in RT plot. Tillage treatments did not alter plant height, SPAD value, ear setting height, ear number, ear length and ear width of waxy corn. However, the RTDT significantly increased stem diameter by 7.7% (27.1 mm vs. 29.1 mm), above-ground biomass by 28.3% (1,170 g m-2 vs. 1,501 g m-2) and ear fresh yield by 22.4% (1,278 g m-2 vs. 1,564 g m-2). The results suggest that tillage management is likely to be an option to secure upland crop production in drained-paddy which has a potential of crop loss by excessive moisture injury. However, the results that we observed were derived from the first-year upland field converted from paddy field, highlighting a necessity of further studies in second- and third-year upland field converted from paddy field to clarify the long-term effect of tillage practices on waxy corn production. Vertical profiles of soil water in upland field converted from paddy field were varied greatly in rotary combined with deep tillage plot (B), but not in rotary only plot (A).

Impacts of biochar application on upland agriculture: A review

Soil degradation has become an emerging global problem limiting sustainable upland crop production. Soil erosion, soil acidity, low fertility, inorganic/organic contamination, and salinization challenge food security and lead to severe economic constraints. Therefore, a new research agenda to develop cost-beneficial amendments for improving upland soil quality and productivity is urgently required. Biochar has been used in recent years to mitigate the problems mentioned above. Application of biochar improves the upland soil quality through significant changes in soil physicochemical and biological properties, thereby substantially increasing crop yield. This review article aims to discuss the effects of biochar on upland soil quality and productivity based on biochar-soil interactions. The yield of various upland crops can be enhanced by biochar-induced increases of nutrient availability and topsoil retention/recovery. Furthermore, biochar can assist in controlling unsuitable soil acidity/alkalinity/salinity and remediating a contaminated soil while increasing the retention of soil organic carbon, water content, and thereby high crop yield. Biochar is strongly recommended as one of the best management practices to meet the challenges of upland agriculture. However, the properties of biochar and soil type should be considered carefully prior to application.

WATER USE EFFICIENCY OF RICE-BASED UPLAND CROP PRODUCTION SYSTEMS IN FLOOD-AFFECTED CHAU PHU DISTRICT, AN GIANG PROVINCE, VIET NAM

Retaining abundant flood water and later using it as crop irrigation water is an issue for the flood-prone area in the Mekong Delta of Viet Nam. The present study aimed to determine an appropriate rice-based upland crop production practice with high water use efficiency and hence the feasibility of retaining flood water for agricultural use in the flood area in the Mekong Delta. On-farm studies were carried out in Chau Phu district of An Giang province from January 2012 to July 2015. Chilli, maize, rice were used as the proxy crops. Crop irrigation water quantity was monitored, and crop yields and economic inputs and outputs were recorded. Results showed that maize or chilli grown on the paddy field were more water-efficient than rice cropping grown alone. Double maize and chilli cropping and rotational rice and maize or chilli cropping required an irrigation water volume of 3,341 m3/ha and 3,686 m3/ha, respectively, compared to 4,289 m3/ha for the commonly-applied double rice cropping. For financial water use efficiency, each cubic meter of water used for crop irrigation yielded a net value of output of 10,950 $VN with double maize and chilli cropping , 6,370 $VN with rotational rice and maize or chilli and 2,790 $VN with double rice cropping practice. These results need to be validated with more farmers’ fields to evaluate the feasibility of the promising crop production systems in larger scale.

Field evaluation of agronomic effectiveness of multi-nutrient fertilizer briquettes for upland crop production

Low nutrient recovery in upland crop production systems has prompted studies to improve the current nutrient management practices to increase fertilizer efficiency. Field studies were conducted in two growing seasons (2012 and 2013) under two land management systems (till and no-till) to evaluate agronomic effectiveness of a multi-nutrient fertilizer briquette (fertilizer briquettes) for upland crop production, using corn as test crop. The fertilizer briquettes were produced through a simple physical compaction of ordinary granular fertilizers with a final nutrient composition of 23.9% N, 19.2% P2O5, 19.1% K2O, 0.9% Zn, and 2.5% S. The agronomic efficiency of the fertilizer briquettes were compared with commercial N sources, urea and ammonium sulfate supplied separately with phosphorus (P), potassium (K), zinc (Zn), and sulfur (S; for urea alone). During the wetter (2013) weather conditions, the fertilizer briquette treatment consistently produced the highest yields in both locations. At Ames Plantation, the fertilizer briquette treatment increased grain yields by ~ 16 and ~ 23% over the treatments having ammonium sulfate and urea granular fertilizers, respectively, and, in Jackson, by 16 and 34% respectively. Nutrient recovery efficiency was also greatest with the fertilizer briquettes treatment. However, during the drier weather conditions (2012), the fertilizer briquettes treatment was the least effective among the three treatments in terms of biomass and grain yields, and nutrient recovery efficiency. We conclude, with adequate rainfall conditions, the fertilizer briquettes could be an efficient fertilizer for upland crop production. However, under drier weather conditions where soil moisture is limited, the fertilizer briquettes may not be an ideal fertilizer source for upland crop production.

Conservation agriculture increases soil organic carbon and residual water content in upland crop production systems

Conservation agriculture involves minimum soil disturbance, continuous ground cover, and diversified crop rotations or mixtures. Conservation agriculture production systems (CAPS) have the potential to improve soil quality if appropriate cropping systems are developed. In this study, five CAPS including different cropping patterns and cover crops under two fertility levels, and a plow-based system as control, were studied in a typical upland agricultural area in northern Mindanao in the Philippines. Results showed that soil organic carbon (SOC) at 0- 5-cm depth for all CAPS treatments generally increased with time while SOC under the plow-based system tended to decline over time for both the high (120, 60 and 60 kg N P K ha -1 ) and moderate (60-30-30 kg N P K ha -1 ) fertility levels. The cropping system with maize + Stylosanthes guianensis in the first year followed by Stylosanthes guianensis and fallow in the second year, and the cassava + Stylosanthes guianensis exhibited the highest rate of SOC increase for high and moderate fertility levels, respectively. After one, two, and three cropping seasons, plots under CAPS had significantly higher soil residual water content (RWC) than under plow-based systems. Results of this study suggest that conservation agriculture has a positive impact on soil quality, while till systems negatively impact soil characteristics.

Livelihood factors and household strategies for an unexpected climate event in upland northern Laos

Climate events pose major challenges to food production and the livelihoods of rural inhabitants in northern Laos, where upland rice using swidden production is an important crop. The onset of the rainy season in this area is one such climate event, and it has occurred earlier and with less regularity in recent years. Not all households are able to cope with these changes. This study examines the ability of local farmers to cope with rice insufficiency. This investigation also clarifies household strategies in dealing with the climate event. We randomly interviewed 63 of 95 household heads, and performed a paired sample t test to examine the significance of differences in three household groups between the 2010 normal climate and the 2011 climate event. The groups were categorized according to rice self-sufficiency in 2011: groups I are households with rice self-sufficiency, group II are those facing a rice shortage of up to 3 months, and group III are those with insufficient rice for over 3 months. We also conducted a one-way ANOVA to examine the significance of differences in livelihood strategies among the three groups. We found that the household labor force was the most important factor in enhancing the villagers’ ability to deal with the climate event and that the level of impact of that event shaped their coping strategies. Households with substantial labor force had more options for coping strategies than those with smaller ones. The villagers faced different levels of impact and adopted different coping strategies accordingly. Non-timber forest product collection was the principle livelihood strategy in response to non-climate factors such as education, access to health services, provision of equipment and clothing, and overcoming the impact of the climate event. Households heavily affected by the early rainy season onset tended to engage in intensive activities such as off-farm activity and outside work, rather than their major livelihood activities in the village (upland crop and livestock production).

Emissions of CO2 and N2O from a pasture soil from Madagascar—Simulating conversion to direct‐seeding mulch‐based cropping in incubations with organic and inorganic inputs

AbstractIn the highlands of Madagascar, agricultural expansion gained on grasslands and cropping systems based on direct seeding with permanent vegetation cover are emerging as a means to sustain upland crop production. The objective of this study was to examine how such agricultural practices affect greenhouse‐gas emissions from a loamy Ferralsol previously used as a pasture. We conducted an experiment under controlled laboratory conditions combining cattle manure, crop residues (rice straw), and mineral fertilizers (urea plus NPK or di‐NH4‐phosphate) to mimic on‐field inputs and examined soil CO2 and N2O emissions during a 28‐d incubation at low and high water‐filled pore space (40% and 90% WFPS). Emissions of N2O from the control soil, i.e., soil receiving no input, were extremely small (< 5 ng N2O‐N (g soil)–1 h–1) even under anaerobic conditions. Soil moisture did not affect the order of magnitude of CO2 emissions while N2O fluxes were up to 46 times larger at high soil WFPS, indicating the potential influence of denitrification under these conditions. Both CO2 and N2O emissions were affected by treatments, incubation time, and their interactions. Crop‐residue application resulted in larger fluxes of CO2 but reduced N2O emissions probably due to N immobilization. The use of di‐NH4‐phosphate was a better option than NPK to reduce N2O emissions without increasing CO2 fluxes when soil received mineral fertilizers. Further studies are needed to translate the findings to field conditions and relate greenhouse‐gas budgets to crop production.

Longitudinal analysis of the road network development and land-cover change in Lop Buri province, Thailand, 1989–2006

Land use and land-cover change (LUCC) is mainly a consequence of human activities such as road network development. In Thailand, the explicit objective of road network development has been to foster economic and social development. The extent of change in roads and land-cover change in Lop Buri between 1989–2006 is analyzed. We hypothesized that road development is a key driver of land-cover change and will cause, substantial changes in areas of forest cover, cultivated food and cash crops. We used land-cover classifications of Landsat imagery and resultant class trajectories to measure change. We then analyzed the relationships between roads, land-cover types, and land-cover trajectories. Overall, cash crops increased while forest and food crops declined between 1989–2006. The relationships between distance to roads and land- cover trajectories indicate that as the distance to roads increase, there are fewer changes in LUCC. The results suggest that in this case study, an increase in road network contributes to an increase in upland crops. In turn, the increase in upland crop production is one of the factors linked to economic development.

Quantifying direct N 2O emissions in paddy fields during rice growing season in mainland China: Dependence on water regime

Various water management regimes, such as continuous flooding (F), flooding-midseason drainage-reflooding (F-D-F), and flooding-midseason drainage-reflooding-moist intermittent irrigation, but without water logging (F-D-F-M), are currently practiced in paddy rice production in mainland China. These water regimes have incurred a sensitive change in direct N 2O emission from rice paddy fields. We compiled and statistically analyzed field data on N 2O emission from paddy fields during the rice growing season (71 measurements from 17 field studies) that were published in peer-reviewed Chinese and English journals. Seasonal total N 2O was, on average, equivalent to 0.02% of the nitrogen applied in the continuous flooding rice paddies. Under the water regime of F-D-F or the F-D-F-M, seasonal N 2O emissions increased with N fertilizer applied in rice paddies. An ordinary least square (OLS) linear regression model produced the emission factor (EF) of nitrogen for N 2O averaged 0.42%, but background N 2O emission was not pronounced under the water regime of F-D-F. Under the F-D-F-M water regime, N 2O EF and background emission were estimated to be 0.73% and 0.79 kg N 2O-N ha −1, respectively, during the paddy rice growing season. Based on results of the present study and national rice production data, subsequently, direct N 2O emissions during the rice growing season amounted to 29.0 Gg N 2O-N with the uncertainty of 30.1%, which accounted for 7–11% of the reported estimates of annual total emission from croplands in mainland China. The results of this study suggest that paddy rice relative to upland crop production could have contributed to mitigating N 2O emissions from agriculture in mainland China.

Denitrification characteristics of subtropical soils in China affected by soil parent material and land use

SummaryForty‐five soil samples were collected from rice paddy land (R), tea garden land (T), forestland (F), brush land (B), and upland (U) in Jiangxi province, a subtropical region of China. These soils were derived from Quaternary red earth (Q), Tertiary red sandstone (S), and granite (G). Their denitrification capacities were determined after treatment with 200 mg NO3−‐N kg−1 soil by measuring changes in NO3−‐N content during a 28‐day anaerobic incubation under N2 gas in the headspace, at 30°C. The subtropical soils studied here were characterized by generally small denitrification capacities, ranging from no denitrification capacity to complete disappearance of added NO3−‐N within 11 days of incubation. With few exceptions, NO3−‐N reduction with incubation time followed a first‐order relationship with reaction constants of 0 – 0.271 day−1, but the data could be simulated better by a logarithmic relationship. Thus, denitrification capacity was determined by the reaction constant of the first‐order reaction, the slope of the logarithmic relationship, and the averaged NO3−‐N reduction rate in the first 7 days of anaerobic incubation (ranging from 0 to 28.5 mg kg−1day−1), and was significantly larger in the soils derived from G than from Q and S for all land uses except for rice paddy land. Soil organic carbon and nitrogen availability are the key factors that determine differences in denitrification capacity among the three soil parent materials. Rice cultivation significantly promoted denitrification capacity compared with the other four land uses and masked the effect of soil parent materials on denitrification capacity. This is most likely due to increases in organic carbon and total N content in the soil, which promoted the population and biological activities of microorganisms which are able to respire anaerobically when the rice soil is flooded. Neither the increased pH of upland soil caused by the addition of lime for upland crop production, nor the decreased pH of the tea garden soil by the acidification effect of tea plants altered soil denitrification capacity. Our results suggest that land use and management practices favour soil carbon and/or nitrogen accumulation and anaerobic microorganism activities enhance soil denitrification capacity.

MORPHOLOGY, PHYSIOCHEMICAL CHARACTERISTICS, AND FERTILITY OF SOILS FROM QUATERNARY LIMESTONE IN LEYTE, PHILIPPINES

Very few studies have been conducted on the nature and characteristics of soils from Quaternary limestones in geologically young islands in the humid tropics. This study examined a hillslope in Leyte, Philippines, with soils from Quaternary (Late Pleistocene) limestone and evaluated their morphology, physiochemical characteristics, and fertility constraints. We evaluated six pedons representing different slope positions, such as summit, shoulder, upper backslope, middle backslope, lower backslope, and footslope. Our data indicate that the soils in the upper slopes (summit, shoulder, and upper backslope) have thin solum, black surface horizon, clayey texture, granular structure, high organic matter and N, high Ca and CaCO3 contents, low contents of nutrients like P, K, Fe, Mn, and B, and are neutral to alkaline pH values. According to Soil Taxonomy, the soils are classified as Typic Calciudolls (summit) and Rendollic Eutrudepts (shoulder and upper backslope), but all three pedons are classified as Calcaric Phaeozems in the World Reference Base system. Conversely, the soils on the lower slopes (footslope and middle and lower backslopes) have thicker solum and higher clay content. They have subangular blocky structures, which turn hard when dry and become plastic and sticky when wet. Like the soils on the upper slopes, they also have neutral to strongly alkaline pH values, have high organic matter, N, Ca, and CaCO3 contents, but are generally low in nutrient contents. They are classified as Typic Eutrudepts (source, Soil Taxonomy) or Calcaric Cambisols (source, World Reference Base). Most soils have high rock fragment contents in their profile. Results also show substantial variations of solum depth at short distances along the slope (i.e., from summit to footslope) and across the slope. The solum depth variability helps explain the commonly observed variations of crop growth in limestone areas. The high clay content of these relatively young soils suggests contribution from limestone parent material and possibly volcanic ash from past eruptions of nearby volcanoes. Our results show that soils developed from limestone have both physical and chemical fertility constraints to upland crop production, which differ between soils even in the same landscape. The overall results indicate that the characteristics and fertility constraints of soils from Quaternary limestones in our study site are largely the influence of the slope position, chemical characteristic of the limestone parent material, and human activities.

Rock phosphate-P enhances biomass and nitrogen accumulation by legumes in upland crop production systems in humid West Africa

Experiments were conducted during 1996–1998 in screen house and in the field in the humid forest zone of Cote d’Ivoire, to evaluate the effects of phosphorus (P) from phosphate rock (PR) on the performance of the root nodulating legume Crotalaria micans grown for 8 weeks. The experimental soils were acid Ultisols with <4 mg/kg extractable Bray-1 P. Tilemsi PR from Mali and triple superphosphate (TSP) were applied at 60 kg P ha−1 (screen house) and 90 kg P ha−1 (field) to the legume. Legume N-fixed (BNF) was estimated by the 15N-isotope dilution and δ15N natural abundance methods, using Cassia obtusifolia L. as a non-fixing legume reference plant. Without P supply, and under the field conditions, C. micans produced less than 1 tonne of biomass and accumulated 29 kg N/ha. The application of PR-P enhanced legume N by about fourfold over the unfertilised control. There was no significant difference between the effects of TSP and PR. Phosphorus application mainly affected the total amount of N accumulated rather than the percentage derived from the atmosphere (%N dfa) per se. Furthermore, the cumulative effects of PR-P on the performance of C. micans greatly improved with time in the screen house. This study confirms that Tilemsi PR is an agronomically effective source of P for short-duration legume green manure (GM) even in the first year of its application to acid P-deficient soils in the West African humid zone.

Population and Upland Crop Production in Nang Rong, Thailand

This paper estimates village-level models of the effects of population variables on the area devoted to upland crop production in Nang Rong district, Thailand. The expansion of upland crops is part of the growth of market agriculture in Nang Rong, and a correlate of deforestation in this setting, The results show that population density (measured as density of village settlement) negatively affects area in upland crops while population growth has a positive effect. Changes in land use associated with population change appear to radiate outward from nuclear village centers. As cash economies are established in rural settings, household formation requires a source of income as well as a subsistence stake. Growth in the population of households is a stronger predictor of the area in upland crops than growth in the number of persons.