Predicting soil moisture condition in arbitrary agricultural lands using the digital soil map and soil physical properties database

To predict soil moisture condition in arbitral agricultural lands by taking spatial distribution of soil type in a watershed into account, we investigated the possible proper methods of determining the soil hydrological parameters using available soil physical properties database of Japanese soils, “SolphyJ”, and the digital soil map. In this study, simulation of soil moisture was conducted at three neighboring locations, including monitoring sites each in Toyama and Fukui cities. The simulated results of soil moisture appeared to be improved when hydraulic parameters were obtained by fitting water retention data of SolphyJ compared to the parameters estimated by neural network with soil texture and dry bulk density data. It is probably because peculiar soil structure in each field could affect the hydraulic properties more than the soil texture. Simulation results also indicated that soil moistures are much different even if they are located in neighbors (<5 km). We concluded that combination of these two databases is useful for estimating soil hydraulic parameters and to predict soil moisture condition in arbitrary agricultural lands.     

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.     

红壤旱地春大豆品种的产量,品质及矿质营养的基因差异

在江西红壤旱地底施氮磷钾肥条件下,６个不同生育期品种的产量均可达到１５００ｋｇ／ｈｍ＾２以上,在气候条件较好的１９９７年,分别达到１７００－２３５０ｋｇ／ｈｍ＾２,产量高低及主要经济性状随品种生育期长短而异,与对照相比,增产率为２．５４％－３５．５３％,主要农艺性状亦存在差异;生育期长的品种比生育期短的品种蛋白质含量低、油分含量高,但蛋白质,油分之和均超过６５％。早熟品种８９０５－１不但产量高出中     

Drainage and irrigation performance of hybrid ditches in converted paddy fields under winter wheat cultivation in Hokkaido

Paddy fields converted into winter wheat fields in Hokkaido, Japan, receive extremely high snowfall, creating a risk of flood damage to crops in spring due to waterlogging of snowmelt runoff and poor drainage. Meanwhile, in June there is relatively little rainfall, and a lack of moisture inhibits winter wheat growth. Therefore, we developed a method involving a series of 30-cm-deep ditches in agricultural fields to be used for drainage during the flood-prone period and for furrow irrigation during the dry period using water drawn from the canals that feed the paddy fields. The ditches are called ‘hybrid ditches’ as they are able to perform both drainage and irrigation functions. In this study, we investigated the optimal construction timing and spacing for hybrid ditches. We also evaluated their ability to improve the drainage and irrigation of winter wheat. We found that the optimal timing for digging hybrid ditches is immediately after sowing, and the inter-ditch spacing for irrigation should be 15 m or less. The hybrid ditches promoted increased soil temperature and healthy development of wheat plants by improving drainage during the flood-prone period. In addition, water was successfully supplied via the hybrid ditches to irrigate the fields in June. Under experimental conditions in which rainfall was excluded, grain yield was 10% higher and percent protein content was more than 1% point greater in the irrigated plot compared with the non-irrigated plot. Grain yield was also observed to increase by 3–29% in demonstration tests conducted at local farms. From these results, we conclude that hybrid ditches are capable of improving the growth and yield of winter wheat by improving drainage and providing irrigation in converted paddy fields in Hokkaido.     

垄体垄沟带状深松技术对重茬大豆根腐病及大豆生育的影响

1995－1997年在大豆重茬条件下，进行了垄体垄沟带状深松技术对大豆根腐病及大豆生育影响的研究。结果表明，带状垄体垄沟深松技术能减轻大豆根腐病的发生，并且使大豆株高、茎粗、根数明显增加，干物质积累量增加。     

不同土壤水分条件下吲哚丁酸钾对大豆根系形态建成及生理代谢的影响

为了研究吲哚丁酸钾（IBA-K）在减轻干旱对大豆根系的伤害中的作用,以垦丰16（干旱敏感型）和合丰50（耐旱型）为材料,采用盆栽法研究IBA-K拌种对两个品种大豆在正常供水、干旱和复水条件下根系形态建成及生理代谢的影响。结果表明,与正常供水相比,干旱胁迫抑制了大豆根系的生长发育,而IBA-K处理后,大豆根系干物质积累量、形态建成、抗氧化酶活性和渗透调节物质含量在不同土壤水分条件下均高于其干旱对照,膜受损程度减轻。IBA-K处理下,大豆根系SOD活性、POD活性、可溶性糖和脯氨酸含量在干旱条件下均显著高于其干旱对照;MDA含量、相对电导率显著低于其干旱对照。IBA-K处理下的两个品种大豆根表面积、根平均直径、根体积、POD活性和CAT活性在复水条件下分别高于其干旱对照,均未达到显著性差异。复水后,IBA-K处理下的垦丰16根干重和总根长分别较其干旱对照显著增加了3.13%和24.51%,合丰50根干重和总根长较其干旱对照未达到显著性差异。IBA-K处理下的合丰50相对电导率和MDA含量分别较其干旱对照显著降低11.80%和15.09%,SOD活性和可溶性糖含量分别较其干旱对照显著增加14.90%和3.94%,垦丰16相对电导率、MDA含量、SOD活性和可溶性糖含量较其干旱对照未达到显著性差异。IBA-K处理下的两个品种大豆根系脯氨酸含量分别较其干旱对照显著增加了10.62%和10.70%。IBA-K处理和不同土壤水分处理对两个品种大豆根系形态和生理指标存在显著或极显著影响,二者间的交互作用无明显调控作用。综上,IBA-K通过提高根系干物质积累量、抗氧化酶活性和渗透调节物质含量,降低MDA含量和相对电导率,减轻干旱胁迫对苗期大豆根系的伤害。     

Quantification of soil surface evaporation under micro-scale advection in drip-irrigated fields

The objective of this study is to quantify soil surface evaporation under micro-scale advection in drip-irrigated fields. A numerical model for estimating soil surface evaporation under micro-scale advection, assuming drip-irrigated fields, is introduced. Results indicate that the soil surface evaporation changes spatially. Soil surface evaporation at the upwind edge of wet soil portions adjacent to dry soil portions increased abruptly. On the other hand, soil surface evaporation at the upwind edge of dry soil portions adjacent to wet soil portions decreased, and condensation was observed. These phenomena were considered to be due to airflows between differing climates. To verify the accuracy of the model, an experiment using a wind tunnel was conducted. The simulated soil surface evaporation results from the model were consistent with the experimental data. The numerical model introduced here is an effective way to quantify soil surface evaporation under micro-advective conditions.     

接种体密度、土壤含水量和土壤温度对大豆疫霉根腐病发生的影响

在人工气候箱内分析测定了接种体密度、土壤含水量和土壤温度对大豆疫霉根腐病发生的影响。结果表明,每克干土中分别接种0、10、50、100、200、300、400、500、600、700个游动孢子,发病率逐渐升高,每克干土中接种400个游动孢子时发病率达到最高,浓度再升高发病率开始下降。在饱和土壤含水量(40%)条件下,土壤温度在10℃~25℃范围内,发病率随温度升高不断增加, 25℃时发病率达到最高,温度再升高发病率降低。在最适温度(25℃)条件下,土壤含水量在15％~40％之间变化时,发病率逐渐升高,当土壤含水量40%时发病率达到最高,土壤含水量再升高发病率下降。     

Predicting water absorption of wheat flour using high shear-based GlutoPeak test

Selection for water absorption, a fundamental wheat quality parameter, has been a challenge in wheat breeding programs due to limited wheat materials available for milling and consequent time-consuming farinograph test. Hence, a high shear-based method, which requires 8 g of flour and less than 10 min per test, was proposed to predict flour water absorption using the Brabender GlutoPeak instrument. Highly significant positive linear relationship (r² = 0.97) was found between GlutoPeak maximum torque and farinograph water absorption for 83 flour samples prepared with Bühler test mill from wheat lines under evaluation in the Canadian wheat variety registration trials. Similar strong correlation (r² = 0.96) was obtained from flours (n = 63) prepared with Quadrumat Junior laboratory mill using small amount of wheat. Flour prepared either with Bühler test mill or Quadrumat Junior mill can be used for predicting water absorption effectively. GlutoPeak maximum torque was found to be independent of dough strength (r² = 0.02) as measured by extensigraph. GlutoPeak test can be a powerful tool for rapid and reliable prediction of water absorption of wheat flour.     

东北黑土区高产大豆R5期根系分布特征

利用钻土法及根系扫描分析系统研究不同产量类型大豆R5期根系在植株周围、株间及垄间土壤中的空间分布特征。结果表明：高产类型大豆根冠比较高，而且单位根长、根表面积的地上部干物质较高。根干重不仅在根系较集中的植株周围及株间0 ~ 30 cm的土层，而且在较深的土层（> 30 cm）中都有较多的分布；根长在植株周围的0 ~ 45 cm土层范围内表现出一定的优势。直径 < 1.0 mm的细根形成了根系的主要部分，根长差异的主要原因不是细根比例的大小，而是细根数量的多少。除株间0 ~ 15 cm土层外，高产大豆各土层的根/土体积比较高。     

Phenotypic variation in root development of 162 soybean accessions under hypoxia condition at the seedling stage

Soybean is often damaged by hypoxia caused by waterlogging at the seedling stage. Hypoxia severely inhibits root development and retards plant growth. We aimed to clarify phenotypic variation in root development under hypoxia condition at the seedling stage using diverse soybean accessions. Root development in 162 accessions was evaluated in hydroponic culture. Substantial changes under hypoxia were investigated by means of WinRHIZO analysis before and after the treatment. We found significant phenotypic variation in hypoxia tolerance in root among the 162 accessions. A principal components analysis indicated an association between hypoxia tolerance and the country of origin. We found three new accessions which have a high ability to develop roots under hypoxia (Kokubu 7, Maetsue zairai 90B, and Yahagi). Root development in selected accessions was also evaluated in soil culture. Root development levels in hydroponic and soil culture were significantly correlated. These results will provide important information on waterlogging damage in regions where waterlogging occurs. The three accessions with hypoxia-tolerant roots might be useful for genetic improvement of waterlogging tolerance of modern soybean varieties.     

Predicting on-farm soybean yields in the pampas using CROPGRO-soybean

Soybean is the main rainfed crop in a wide range of latitudes and sowing dates of the Argentine Pampas. It is sown alone or as a second crop after other winter and summer crops. Modelling approaches have proved to be helpful in the decision making process. The on-farm evaluation of CROPGRO is rather difficult since input data are scarce and frequently of worse quality than those from experimental works. Moreover, CROPGRO simulation of water dynamic processes and their relation with biomass production has not been comprehensively evaluated in soybean crops. The aims of this study were (i) to evaluate the CROPGRO-soybean performance, with emphasis on water demand and supply and biomass production under water limited conditions, (ii) to generate a revised CROPGRO model improving those aspects, and (iii) to compare simulations outputs using the original and the revised CROPGRO models, with on-farm crop data set. In the revised model, we multiplied potential evapotranspiration by 1–1.22 when LAI increased from 0 to ≥4.0. We set a root extension rate of 4.0 cm/thermal day and a maximum rooting depth of 2.5 m. Finally, we included a nonlinear equation to simulate the relationship between relative transpiration and relative gross photosynthesis. The ability of the revised CROPGRO-soybean to simulate water content depletion and biomass production was tested against several experiments with an imposed drought period. We also calibrated cultivar parameters using “ad hoc” tests in a range of environments (combinations of sowing dates and locations). The models were evaluated with data from 155 commercial farms. V (%) (root mean square error as percentage of the observed mean) for the total cycle length, vegetative period, and reproductive phase simulations were 7, 13 and 15%, respectively. The revised CROPGRO was more accurate in simulating crop yield, biomass, harvest index and yield numeric components. V (%) values ranged from 11 to 17% (revised version) and from 13 to 22% (original version). Besides, V (%) values for yield were 16% with the revised model versus 32% with the original one, considering only paddocks with higher water stress level. The robust prediction of phenology, biomass and yield components obtained with the revised model across different environmental conditions, support its use in the decision making process of the soybean crop at the farm scale.     

大豆田除草剂混用技术及药害

为了指导大豆田杂草防除技术,介绍了大豆田杂草发生的主要种类与特点,除草剂混用品种的选择,除草剂药害的分类,除草剂药害调查分级与除草剂混用性能比较等,以及大豆田杂草防除技术和施用除草剂混剂不当造成的药害.     

粘土地夏大豆免耕窄行密植技术

粘土地夏大豆采用免耕窄行密植技术,可以适时早播,缩行增苗,营造合理的群体结构,提高光能和土地利用率。该技术与化学调控和化学除草技术相配套,适于机械化作业,达到节能高产的目的。     

Nitrous oxide emissions from paddy fields under different water managements in southeast China

Water management is recognized as one of the most important factors in regulating nitrous oxide (N₂O) emissions from paddy fields. In China, controlled irrigation (CI) is widely applied because it has been proved highly effective in saving water. During the rice-growing season, the soil in CI paddy fields remains dry 60–80% of the time compared with soil irrigated by traditional methods. This study aims to assess N₂O emissions from paddy fields under CI, with traditional irrigation (TI) as the control. The cumulative N₂O emission from CI paddy fields was 2.5 kg N ha⁻¹, which was significantly greater than that from TI paddy fields (1.0 kg N ha⁻¹) (P < 0.05). Soil drying caused substantial N₂O emissions. The majority (73.9%) of the cumulative N₂O emission from CI paddy fields was observed during the drying phase, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the drying phase. More and significantly higher peaks of N₂O emissions from CI paddy fields (P < 0.05) were also detected. These peaks were observed ~8 days after fertilizer application at water-filled pore spaces (WFPS) ranging from 78.0 to 83.5%, soil temperature ranging from 29.1 to 29.4°C, and soil redox potential (Eh) values ranging from +207.5 to +256.7 mV. The highest N₂O emission was measured 8 days after the application of base fertilizer at a WFPS of 79.0%, soil temperature of 29.1°C, and soil Eh value of +207.5 mV. These results suggest that N₂O emissions may be reduced obviously by keeping the WFPS higher than 83.5% within 10 days after each fertilizer application, especially when the soil temperature is suitable.     

Stomatal behavior of potatoes under nonlimiting soil water conditions

Field studies were conducted to examine the relative effects of net irradiance (R_n), air vapor pressure deficit (VPD) and leaf water potential (Ψ₁), on leaf conductance, (C₁) of well-watered potatoes. Conductances of sunlit, surface-layer leaves for the cultivars Russet Burbank, Kennebec and Lemhi Russet were positively correlated with R_n (r²=0.79, 0.83 and 0.62, respectively) for R_n between 100 and 650 Wm^-2. Leaf conductance (cm s^-1) for all three cultivars was described by the linear relation: C₁=0.871 +0.0028 R_n (r²=0.73). Mean C¹ for a full Russet Burbank canopy, comprised of measurements from both sunlit and shaded leaves, was also linearly related to R_n. Although VPD and Ψ₁ were significantly correlated with C₁ (r²=0.44 and 0.46, respectively), the results of multiple regression analysis showed that they had no additional effect on C¹ beyond that attributed to R_n. These results indicate that potato leaf conductance is primarily related to irradiance under nonlimiting soil water conditions.     

江西省红壤丘陵春大豆高产配套栽培技术

春大豆在江西是一种增加复种指数改进轮作、间、套多熟制的主要作物 ,但由于品种和栽培技术的原因 ,产量比较低 ,影响了我省春大豆的发展。本文在九·五国家重点推广项目“南方红黄壤大豆良种及配套技术推广”五年多的实施过程中 ,根据高产试验、示范和高产攻关中出现的一批 3 0 0 0kg/hm2 以上的高产典型经验 ,总结提出了一套江西省红壤旱地春大豆高产配套栽培技术。     

Application of infrared thermography to assess cassava physiology under water deficit condition

ABSTRACT

Water deficit stress is a major factor that inhibits the overall growth and development in cassava (Manihot esculenta), leading to decreased storage root yield. We conducted a study to investigate whether thermal sensing could be used to indicate water deficit stress and the health and yield of cassava crops in field. The objective of the study was to use thermal imaging to determine relationship between crop water stress index (CWSI) and physiological changes, and to identify the critical CWSI point in fields of cassava cv. Rayong 9 under well-irrigated and water-deficit conditions. At the time of storage root initiation (85 DAP [day after planting]), thermal imagery was collected and the physiological changes and growth characters were measured prior to storage root harvesting (162 DAP). Thermal infrared imager was used to measure the canopy temperature and CWSI of cassava plants. Net photosynthetic rate (P_n), stomatal conductance (g_s) and transpiration rates (T_r) of cassava plants under water deficit conditions for 29 d (114 DAP) were significantly decreased, leading to delayed plant growth as compared to those under well-irrigated conditions. In contrast, air vapor pressure deficit (VPD_air) and CWSI in drought-stressed plants were higher than well irrigated plants. High correlations between T_r/g_s/P_n and CWSI were observed. The study concludes that CWSI is a sensitive indicator of water deficit stress caused due to stomatal function.

Abbreviations: CWSI: crop water stress index; DAP: day after planting; Pn: net photosynthetic rate; gs: stomatal conductance; Tr: transpiration rate; VPDair: air vapor pressure; RMSE: root mean square error     

大垄垄上行间覆膜对土壤水分、温度及大豆产量形成的影响

为探讨大豆大垄垄上行间覆膜的增产机制,以垦丰15、垦丰16两个大豆品种为材料,在田间进行大垄垄上行间覆膜和不覆膜处理,研究了覆膜阶段土壤水温状况及植株形态指标变化。结果表明,行间覆膜对土壤的增温作用在大豆生育前期内呈“U”型变化,在增加耕层含水量、改善根系生长环境方面起到重要作用,覆膜大豆产量明显高于对照。     

Plasticity in root system architecture of rice genotypes exhibited under different soil water distributions in soil profile

ABSTRACT

The root system architecture (RSA) has been reported to be determined by several root traits such as branching, elongation, and growth angle. This study aimed to evaluate the genotypic variation of plasticity in RSA in response to different soil water distributions in a soil profile. IR64 (shallow root system), YTH183 (adapted to rainfed lowland conditions due to high plasticity in root elongation), and Kinandang Patong (KP – deep root system) were grown in PVC root boxes for 34 days under continuously waterlogged conditions and with soil moisture fluctuations (SMF). For SMF, watering was done from the top of the root box (TI-SMF) or from the bottom of the root box (BI-SMF). A water gradient was observed more clearly in BI-SMF than in TI-SMF, while mean soil moisture content in the root box was kept at around 23% (v/v) after first irrigation in both SMF treatments. RSA changed drastically with SMF in all cultivars, all of which tended to shift root distribution to deeper soil layers in response to SMF. Such changes in RSA resulted from different degrees of plasticity exhibited mainly in nodal root and L-type lateral root development. YTH183 showed a greater ability to change its root growth angle and thus its root distribution in the deeper soil layer compared to IR64 and KP under SMF, indicating that YTH183 could help to improve RSA in cultivars adapted to SMF.