Nutrient Deficiency in the Rice-Stylo (Stylosanthes guianensis) Relay-Intercropping System in Rainfed Lowland Rice Ecosystem in Northeast Thailand

Abstract

The rice-stylo (Stylosanthes guianensis) relay-intercropping system in paddy fields has previously been shown to increase agricultural productivity in Northeast Thailand, but successive relay-intercropping conducted without irrigation and fertilization during the stylo cropping has resulted in reduced production of stylo. The aim of this study was to determine the effect of nutrient deficiency on the stylo production. The experiment was conducted using pots to control fertilization accurately. The results showed that, after three successive relay-intercroppings, the soil was severely deficient in sulfur, phosphorus, and molybdenum. Sulfate application to the soil after the successive relay-intercroppings was suggested to improve stylo production. We recommend the use of a rain-fed shallow, favorable subecosystem as a field for stylo production in relay-intercropping and the stylo production with a cycle of several years.     

Toposequential Variation in Soil Fertility and Rice Productivity of Rainfed Lowland Paddy Fields in Mini-Watershed (Nong)in Northeast Thailand

Abstract

Mini-watersheds called Nongin Thai are geographical components of rainfed lowland rice culture in Northeast Thailand, and constitute distinct units in understanding environmental constraints for low and unstable rainfed rice production there. The toposequential variation of soil fertility and its relation to rice productivity within mini-watersheds, was examined by phytometry of sampled soils and field measurements of rice growth and yield. The phytometry experiment with irrigated potted rice using soils sampled from various rice fields within each mini-watershed, revealed that soil fertility as evaluated by rice dry matter production showed a 5 times difference among the fields at most. The difference in the soil fertility was ascribed primarily to that in nitrogen (N) supply capacity, which itself had a strong correlation with soil organic carbon (SOC) content. Accordingly, the biomass production of pot-grown rice was proportional to SOC. content, which suggested the usefulness of SOC as an index for soil fertility evaluation. The effect of clay on the soil fertility was much less than that of SOC. The actual rice yield in each field also showed quite large field-to-field variation, most of which was explained by the SOC content, rice growth duration and fertilizer application rate even though water availability also affected the yield. The yield positively correlated with growth duration and hence with earlier transplanting. Both SOC and clay contents of fields showed steep gradients with ascending field elevation within mini-watersheds, resulting in a marked toposequential distribution of rice yield. The toposequential distributions of SOC and clay contents imply that rice culture after deforestation accelerated soil erosion from upper to lower fields. The large toposequential gradient in soil fertility requires different resource and crop management for each toposequential position, in order to improve rice productivity of the mini-watershed as a whole.     

Genotypic Variation in Response of Rainfed Lowland Rice to Prolonged Drought and Rewatering

Abstract

Duration of the drought period is important for plant response during drought and after rewatering. We hypothesized that, if drought duration is extended, (1) high seedling vigor and rapid development of a deep root system will not be advantageous, and (2) osmotic adjustment will be more important. Six diverse rice (Oryza sativa L.) genotypes were selected from rainfed lowland germplasms to examine the development of a deep root system and osmotic adjustment, and their relationship with biomass production during drought and after rewatering, under two different drought durations (shorter and prolonged) in the greenhouse. NSG19 and KDML105 had greater seedling vigor (larger seedling biomass), developed a deep root system earlier in response to drought, extracted soil water more quickly, and their pre-dawn leaf water potential declined more rapidly during the prolonged drought period. These two genotypes showed superior drought recovery even after a prolonged drought period in which they suffered a greater reduction in transpiration, water use efficiency, and biomass production. The superior recovery ability was associated with larger plant size by the end of the drought period rather than with plant water status during drought, such as osmotic adjustment or leaf water potential. Osmotic adjustment was greater during prolonged drought periods (ca. 0.7 MPa) than during shorter drought periods (ca. 0.5 MPa), and lower osmotic adjustment was mostly associated with a higher leaf water potential. Genotypic variation in osmotic adjustment was observed, but there was no clear relationship between osmotic adjustment and biomass production during drought periods. These patterns of response of rice seedlings to drought and rewatering in the greenhouse should help to explain the patterns of adaptation of rainfed lowland rice in the field. Selection for drought recovery ability should be an advantageous strategy for early season drought.     

Effects of Soil Clay Content on Water Balance and Productivity in Rainfed Lowland Rice Ecosystem in Northeast Thailand

Abstract

Water availability is one of the determinants of productivity of rainfed lowland rice (Oryza sativa L.). Quantifying water losses from a paddy field, such as deep percolation and lateral seepage, assists estimation of water availability to the rice crop and development of appropriate water management in the lowlands. The main objective of this study was to evaluate paddy water availability and productivity across various soils in Northeast Thailand. The daily rate of downward water flow from standing water in the field (D) varied between 0 and 3 mm day^-1 from clayey to sandy soils when the standing water was connected to groundwater table. However, when the standing water was separated from groundwater table, D increased up to 5 mm day^-1 on soils with very low clay content in the topsoil. Daily net lateral water flow from the field (L) averaged over the season varied between 5 and 24 mm day^-1 for the outflow and between 3 and 16 mm day^-1 for the inflow. Both the inflow and outflow tended to be associated negatively with the soil clay content. The seasonal water loss through D plus L during the growing season in the lowlands was also negatively related to the soil clay content. The yield of a major rainfed lowland rice cultivar in Northeast Thailand (KDML105) varied from 2 to 4 t ha^-1 across the region, and the water productivity (the ratio of grain yield to cumulative rainfall from transplanting/seedling establishment to maturity) ranged from 3 to 9 kg ha^-1 mm^-1. High clay soils could provide good standing water until late in the growing season, so the high production efficiency was measured on such soils.     

Increasing Production of Rainfed Lowland Rice in Drought Prone Environments

Summary

Drought is a major production constraint of rainfed lowland rice grown in Thailand and Laos. Adverse soil conditions also reduce yield. In an attempt to increase rainfed lowland rice production in these countries, a major collaborative international project was conducted during a 6-year period in the region. The objectives of the project were to quantify production constraints, determine genotypic variation in yield, and identify an effective breeding strategy. A rice simulation model was developed also and used to investigate the potential impact of strategies for genetic improvement and agronomic management.

Four major physical or biological constraints to higher production levels of rainfed lowland rice were identified, (1) the lack of standing water at the appropriate time of transplanting, (2) severe water stress that often develops at the end of the growing season, (3) low yield potential of the present cultivars, particularly in Thailand, and (4) adverse soil conditions including low pH and low soil fertility. The results of the field experiments and simulation modelling exercises showed that the influence of these constraints can be reduced and yield increased by several methods : in particular, choice of appropriate cultivars and time of sowing to match crop phenology with water availability, application of appropriate fertilizer, adoption of high yielding cultivars, adoption of direct seeding in place of the traditional transplanting system, and reduction of percolation water loss from the paddies.

A technology package currendy being investigated for the rainfed lowland rice is direct seeding early in the season, using cultivars that flower by the end of the rainy season, with application of organic or chemical fertilizer. The appropriate cultivars are early flowering and short-intermediate statured, possess high yield potential and ability to maintain favourable plant water status at flowering, and have the ability to establish well and compete against weed under direct seeding.     

Identification of Nutrients Limiting Rice Growth in Soils of Northeast Thailand under Water-Limiting and Non-Limiting Conditions

Summary

Glasshouse nutrient omission trials are useful in identifying nutrient limitations for plant growth in soils under the same environmental conditions. Soils of low fertility are commonly used for production of rainfed lowland rice (Oryza sativa L.), and the crop often encounters water stress. Nutrient requirements may be modified when standing water disappears from the field. Two experiments with rice seedlings were conducted in a glasshouse at Ubon Rice Research Center, Thailand, to identify the nutrients which limit rice growth in soils of Northeast Thailand, and to determine whether nutrient limitations are affected by water availability. In Experiment 1, rice was grown on two soils (Roi et and Ubon series) under well-watered and water-limiting conditions, and 15 nutrient treatments were imposed. In Experiment 2, six soils from Northeast Thailand were examined using the same 15 nutrient treatments. The nutrients which clearly limited the growth of rice plants in soils of Northeast Thailand were nitrogen (N) and phosphorus (P). In some cases, potassium (K) and sulfur (S) also limited growth, and in one soil zinc (Zn) and boron (B) also limited growth. A shortage of N was the most important limitation for plant growth in all soils except one in which P was more important. The low supply of P decreased plant height and leaf area development during early growth ; low N supply had a greater effect later during growth. The omission of P had a larger detrimental effect on growth when water supply was limited. In the Roi et soil, the omission of S had a large effect on leaf area and total dry matter production only under water stress conditions, but this was not found in the other soils examined. These results from glasshouse studies show that the nutrients limiting rice growth depend on soil type and water availability in soils of Northeast Thailand.     

Estimating Percolation and Lateral Water Flow on Sloping Land in Rainfed Lowland Rice Ecosystem

Abstract

Quantifying water losses in paddy fields assists estimation of water availability in rainfed lowland rice ecosystem. Little information is available on water balance in different toposequence positions of sloped rainfed lowland. Therefore, the aim of this work was to quantify percolation and the lateral water flow with special reference to the toposequential variation. Data used for the analysis was collected in Laos and northeast Thailand. Percolation and water tables were measured on a daily basis using a steel cylindrical tube with a lid and perforated PVC tubes, respectively. Percolation rate was determined using linear regression analysis of cumulative percolation. Assuming that the total amount of evaporation and transpiration was equivalent to potential evapotranspiration, the lateral water flow was estimated using the water balance equation. Separate perched water and groundwater tables were observed in paddy fields on coarse-textured soils. The percolation rate varied between 0 and 3 mm/day across locations, and the maximum water loss by lateral movement was more than 20 mm/day. Our results are in agreement with the previously reported findings, and the methodology of estimating water balance components appears reasonably acceptable. With regard to the toposequential variation, the higher the position in the topoesquence, the greater potential for water loss because of higher percolation and lateral flow rates.     

Nitrogen Balance in Forage Rice (Oryza sativa L. cv. Tachisuzuka) Cultivation in Pots with Animal Manure Application

Abstract

Experiments were conducted to evaluate the nitrogen (N) balance in forage rice cultivation using animal manure in 1/2,000a Wagner pots in a greenhouse. The cattle manure and poultry manure were applied at 3 levels of N (0, 14, 28 g available N m^–2) without additional chemical fertilizer application. The pots were designed to simulate the fluid percolation in the paddy field. The results indicated increasing levels of N input improved plant height, tiller number, SPAD value and biomass (straw, grain and root) production, however, N leaching from soil (Andosols) due to percolating water also increased. The planting of rice plants proved to reduce 30% of the N leaching loss. N use efficiency, the ratio of N uptake by plant per unit N application, decreased in higher N application. The N uptake by the above-ground parts occupied about 66% of the whole plants.     

Comparative analysis of farmers engaged in participatory research to cope with climate change versus non-participants in Northeast Thailand

ABSTRACT

To assess the extent of improvement of rainfed rice production by using a participatory approach, we compared research project participants and non-participants (total of 206 rice-growing households) with regard to yield variability and their perspective on climate change at seven sites in Northeast Thailand. The participants were characterized by membership in local groups, an active learning attitude, and confidence in their farming. Compared to non-participants, the participants produced crops with higher yield and had more knowledge about the Intergovernmental Panel on Climate Change (IPCC) message and advanced farming technologies. Both groups had similar reactions to past climatic damage experiences, but the participants tended to have a more positive attitude about adaptation to climate change and mitigation by refraining from residual straw burning than the non-participants. The farmers’ attitude about adaptation to climate change was positively associated with their active learning and close relationship with researchers. There was a large yield gap between the bottom 10 percentile farmers (0.63 t/ha) and the top 10 percentile farmers (4.05 t/ha), with an average yield of 2.18 t/ha. Yield was associated with the level of market orientation, with the market-oriented farmers attaining higher yield, including yield from broadcast seeding (2.71 t/ha), than the subsistence farmers (1.66 t/ha). Our findings suggest that technical improvement of rice production in the region by using the participatory approach could be enhanced by selecting participants who are linked with local groups, tend to be market orientated, and are willing to learn with researchers.     

全球水稻生产与稻作生态系统概况

1961—2001年，全球水稻总产、面积和单产分别增长171．3％，30．9％和107．0％。在总产增长中，收获面积增加贡献27．8％，单产提高贡献72．2％，水稻总产增长主要由单产的提高所致。亚洲是主要的产稻区，其水稻总产和收获面积分别占全球的90％和91％。全球各产稻国水稻平均单产差异很大，水稻增产关键在于提高中低产国家和地区的水稻单产水平。全球稻田中，灌溉稻田、雨灌稻田、早稻田和深水稻田分别占54％，3l％，11％和4％。不同水稻生态系统的地区分布中，灌溉稻和雨灌稻主要分布在亚洲，分别占93．0％和95．5％，深水稻主要分布在亚洲和非洲，分别占67．3％和25．0％，早稻主要分布在亚洲、美洲和非洲，分别占57．1％，20．0％和19．1％。     

Evaluation of Transplanting Date and Nitrogen Fertilizer Rate Adapted by Farmers to Toposequential Variation ofEnvironmental Resources in a Mini-Watershed (Nong) in Northeast Thailand

Environmental resources for rainfed rice production show large variability even within a small area in Northeast Thailand, and it is said that farmer’s management is well adapted to the variability. This study evaluated transplanting date and nitrogen (N) fertilizer rate in the management to improve rice productivity. The effect of transplanting date and N fertilizer rate on rice productivity was analyzed by investigating rice growth, and also by dividing rainfed rice fields located in a mini-watershed into 4 subecosystems: (1) medium deep water, waterlogged (MDW), (2) shallow water, favorable (SWf), (3) shallow water, drought- and submergence-prone (SWds), and (4) shallow water, drought-prone (SWd). Rice grew at almost a constant rate until maturity and the growth rate was higher at a lower field. The difference in productivity was derived from not only a water condition but also soil fertility, and was associated with the rate of N uptake. Small leaf area index was found to be one of the causes for low productivity in rice. Statistic analysis showed that earlier transplanting increased biomass production in all subecosystems. The biomass-increase resulted in a higher yield in SWds and SWd fields while it resulted in a reduced harvest index (HI) and did not increase yield in MDW and SWf fields. The effect of N fertilizer was apparent in the field where rice biomass was small due to later transplanting or unfertile soil, but the effect was generally small. Earlier transplanting in upper fields and later transplanting in lower fields in mini-watersheds were suggested to improve rice production, and proper distribution of N fertilizer use is considered necessary.     

湘南双季稻区气候特点与两系杂交稻秋季制种技术

分析了湘南地区的气候特点与两系杂交稻制种季别的关系,认为湘南双季稻区两系杂交稻制种以发展秋制为宜。秋制中不育系育性转换敏感期安排以８月上旬为最佳,抽穗扬花授粉期可安排在８月１６日～９月５日之间,以８月下旬为优。对两系杂交稻秋季制种主要技术进行了总结。     

2011年福建省杂交中稻新品种生产试验小结

对10个中稻新品种与对照Ⅱ优明86在大田生产条件下的产量,抗逆性等特征特性进行生产试验,结果表明川优2189、两优616、福两优1586等品种适合中高海拔地区作中稻栽培;广优2186、广优3301、中浙优1号、花2优3301等品种适合高海拔区域作中稻栽培。     

湘南丘岗地区水稻轻简施肥技术的效应研究

通过田间小区试验,系统研究了在几种轻简施肥技术条件下双季早、晚稻的生育特性、养分吸收规律、肥料养分的当季利用率、经济性状和产量效应以及土壤速效养分的变化规律。结果表明：在轻简施肥技术条件下,双季稻前期早发不明显,中期成穗率高,后期根旺叶健不早衰;早、晚稻不同生育时期的干物质积累量与养分的吸收量具有相似性;早稻前期氮、磷、钾吸收量最低,绝大部分氮、磷、钾养分是在中、后期吸收的,晚稻前期的氮、磷、钾吸收量明显高于早稻,后期的氮、磷、钾吸收量大多低于早稻,不同处理之间差异不大。各轻简施肥处理均能提高早稻对氮和磷的表观利用率,以“湘珠专用肥”处理效果最好,但不能提高早稻对钾的表观利用率;晚稻轻简施肥处理“湘珠专用肥”也能明显提高水稻对肥料氮和钾的表观利用率。轻简施肥处理的水稻产量明显高于当地习惯施肥处理。     

土壤类型对东北粳稻光合物质生产特征及稻米品质的影响

 以响水火山玄武岩天然石板地、人造石板地和附近非石板地为试验对象,研究了不同土壤类型对东北粳稻光合物质生产特征及稻米品质的影响。结果表明：1）非石板地同天然石板地、人造石板地相比,各时期单茎干物质量差异达到显著或极显著水平;拔节至成熟期,非石板地群体干物质积累量明显高于天然石板地和人造石板地,后两者间差异不显著;2）不同土壤类型间水稻叶面积指数在拔节期差异不显著,拔节后,叶面积指数差异达到显著或极显著水平,且叶面积指数表现为非石板地>天然石板地>人造石板地;3）有效叶面积率在不同土壤类型间没有显著差异,而高效叶面积率不同土壤类型间差异达极显著水平,非石板地最高,天然石板地次之,人造石板地最低;4）播种至拔节期、拔节至抽穗期、抽穗至成熟期及全生育期总的光合势,均表现为非石板地最高,天然石板地次之,人造石板地最低,且差异都达到显著或极显著水平;5）供试品种在火山玄武岩天然石板地上种植,其糙米率、整精米率、垩白米率、垩白度、胶稠度、蛋白质含量及食味评分均高于人造石板地和非石板地,而直链淀粉含量却低于人造石板地和非石板地。     

Anatomy of Nodal Roots in Tropical Upland and Lowland Rice Varieties

abstract

Nodal root anatomy was compared among twelve upland and lowland rice (Oryza sative L.) varieties with tropical origin which were grown in hydroponic culture and under field conditions. The traditional upland japonica varieties showed the largest diameter of root, stele, and xylem vessel followed by modern upland varieties. There was a clear varietal difference in the ratio of stele to root diameter, which was associated with the genetic group rather than with the ecosystems. The japonica varieties had a significantly larger stele diameter relative to the root diameter than indica and aus varieties. The indica and aus varieties displayed more xylem vessels per unit area of stele than the japonica varieties, but the diameter of xylem vessel was smaller. Equivalent xylem vessel diameter (De) was more dependent on the number of xylem in the indica varieties than in the japonica varieties. Distinctly different types of sclerenchyma anatomy were identified among the varieties. The development of sclerenchyma was classified into four different types based on thickening of cell wall in the outer cortical parenchyma and the number of sclerenchymatous cell layers. Like the xylem anatomy, the varietal differences in sclerenchyma development were more associated with genetic group rather than the ecotype. The japonica varieties had higher frequency of the types which have a doubled cell layer in sclerenchyma with thick cell wall than indica and aus. The difference among the genetic groups was nearly consistent across growing conditions, aerobic and submerged soils. These results indicated that sclerenchyma development is controlled by a genetic factor.     

高光效栽培模式下东北粳稻光合物质生产特征研究

以东农428和龙稻5号为试验材料,对不同栽培模式下东北粳稻光合物质生产特征进行研究。结果表明,适宜垄距下采用高光效栽培模式,水稻的干物质积累、运转及叶面积、光合势等物质生产和光合生产特征明显优于其他栽培模式,其成熟期群体干物质量和产量比常规栽培分别高1.75~2.51 t/hm~2和2.66~3.78 kg/30 m~2。同为高光效栽培模式,(20+40)cm×15 cm的垄距处理其成熟期群体干物质量和产量明显高于(20+50)cm×15 cm的垄距处理,分别高2.00~2.67 t/hm~2和2.91~4.95 kg/30 m~2,说明行距超出适宜范围其群体干物质积累反而下降,不利于水稻高产群体的形成。     

建国以来渝东北地区水稻品种演替分析与展望

建国至今,渝东北地区水稻品种经历了高秆良种、矮秆良种、杂交稻品种三个重要的推广时期。历时最长、作用最大的杂交水稻推广期,又经历了推广初期的摸索,到汕优2号、汕优63、D优63主推组合的确立,再到杂交稻多组合区域"集团当家,轮换种植"推广模式的确立等发展阶段,有效推动了渝东北地区水稻生产的发展。目前该地区水稻生产呈现出品种数量明显增多、单个品种面积下降的趋势。今后水稻品种的选择推广应向抗病、高产、优质、综合性状优良的方向发展。     

Yield of rice under water and soil salinity risks in farmers’ fields in northeast Thailand

This study focused on the variability of rice yield under water and soil salinity risks in farmers’ fields in northeast Thailand. A rice plot was monitored in 24, 16 and 11 farmers’ fields during the rice seasons 2005, 2006 and 2007, respectively. The results emphasized that few plots were continuously submerged during the 2005 season, when rainfall was low. Drought significantly affected the rice yield, yield components and the internal efficiency (IE) of the absorbed nutrients, while slight soil salinity had the only significant effect of increasing the IE of potassium (IEK). In the very rainy 2006 and 2007 seasons, most fields were continuously submerged, and in contrast to 2005, the slight soil salinity that was recorded had significant effects not only on IEK, but also on rice yield, spikelet sterility and 1000-grain weight. The yield decrease due to drought was about 87% and that due to salinity was 20%. When neither salinity nor water were limiting, the soil nutrient supply was high enough to achieve about 80% of the maximum yield reported in the literature for the rice cultivar in this area. As both drought and salinity risks are hardly avoided by the current farmers’ management they should be taken into account in the way technical recommendations to farmers are formulated.