Middle Growth Stages Research Articles

Characterization of the natural enemy community attacking cotton aphid in the Bt cotton ecosystem in Northern China.

Planting Bt cotton in China since 1997 has led to important changes in the natural enemy communities occurring in cotton, however their specific effect on suppressing the cotton aphids (being notorious in conventional cotton ecosystem) has not been fully documented yet. We observed strong evidence for top-down control of the aphid population, e.g. the control efficiency of natural enemies on cotton aphid increased significantly in open field cages compared to exclusion cages, accounted for 60.2, 87.2 and 76.7% in 2011, 2012 and 2013 season, respectively. The cotton aphid populations peaked in early June to late July (early and middle growth stages) in open field cotton survey from 2011 to 2013. The population densities of cotton aphids and natural enemies were highest on middle growth stage while lowest densities were recorded on late stage for aphids and on early plant stage for natural enemies. Aphid parasitoids (Trioxys spp., Aphidius gifuensis), coccinellids and spiders were key natural enemies of cotton aphid. Briefly, natural enemies can suppress aphid population increase from early to middle plant growth stages by providing biocontrol services in Chinese Bt cotton.

Early Albian (Early Cretaceous) douvilleiceratid ammonites from Haida Gwaii, British Columbia, Canada

AbstractThe early Albian to mid-Albian cosmopolitan genusDouvilleicerasis represented in the Haida Gwaii archipelago of western British Columbia by five species,D.mammillatum(Schlotheim),D.offarcinatum(White),D.scabrosumCasey,D.spiniferum(Whiteaves), andD. aff.spiniferum(Whiteaves). Specimens of one of these taxa,D.spiniferum, are particularly abundant on Haida Gwaii and the species is discussed with respect to its morphological variability and ontogenetic development. The important morphological features for taxonomic criteria of the genusDouvilleicerasare the mode of tuberculation, the pattern of ribbing, and the proportions of the shell in the middle growth stage.

The Impact of Sunlight Conditions on the Consistency of Vegetation Indices in Croplands—Effective Usage of Vegetation Indices from Continuous Ground-Based Spectral Measurements

A ground-based network of spectral observations is useful for ecosystem monitoring and validation of satellite data. However, these observations contain inherent uncertainties due to the change of sunlight conditions. This study investigated the impact of changing solar zenith angles and diffuse/direct light conditions on the consistency of vegetation indices (normalized difference vegetation index (NDVI) and green-red vegetation index (GRVI)) derived from ground-based spectral measurements in three different types of cropland (paddy field, upland field, cultivated grassland) in Japan. In general, the vegetation indices decreased with decreasing solar zenith angle. This response was affected significantly by the growth stage and diffuse/direct light conditions. The decreasing response of the NDVI to the decreasing solar zenith angle was high during the middle growth stage (0.4 < NDVI < 0.8). On the other hand, a similar response of the GRVI was evident except in the early growth stage (GRVI < 0). The response of vegetation indices to the solar zenith angle was evident under clear sky conditions but almost negligible under cloudy sky conditions. At large solar zenith angles, neither the NDVI nor the GRVI were affected by diffuse/direct light conditions in any growth stage. These experimental results were supported well by the results of simulations based on a physically-based canopy reflectance model (PROSAIL). Systematic selection of the data from continuous diurnal spectral measurements in consideration of the solar light conditions would be effective for accurate and consistent assessment of the canopy structure and functioning.

Differences in transport of photosynthates between high-and low-yielding Ipomoea batatas L. varieties

Previous studies have focused mainly on the accumulation of photosynthates and less on their distribution in sweet potato (Ipomoea batatas L.). In addition, the effect of photosynthate accumulation in root tubers on photosynthate distribution was not considered. Thus, a field experiment was carried out from May to October (2011 and 2012) to clarify the differences in photosynthate transport between high- and low-yielding sweet potato. This study mainly focused on the photosynthetic capacities of leaves, photosynthate distribution, and characteristics of photosynthate accumulation in root tubers. Results showed the high-yielding varieties displayed the higher fresh root tuber yield and the economic coefficient than the low-yielding varieties. They also showed greater net photosynthetic rate with a pronounced increase at the early and middle growth stages (8.9% and 11.4%, respectively). After the growth peak, the leaf area index (LAI) of the high-yielding varieties decreased with time and was maintained at 2∼3 until harvest, whereas the LAI of the low-yielding varieties decreased slowly. The high-yielding varieties reached the 13C distribution rate ≥ 50% at the early (2011, 2012) and middle (2011) growth stages, whereas the low-yielding varieties reached it at the late (2011) or middle (2012) growth stages. At harvest, the 13C distribution rates in the branches and root tubers of the high-yielding varieties were 6.0–20.3% and 73.7–91.2%, respectively, whereas those of the low-yielding varieties were 29.6–34.7% and 60.7–63.5%, respectively. The high-yielding varieties showed the remarkable initial potential in root tubers, which was much better than that of the low-yielding varieties. The high-yielding varieties also produced heavier root tubers and the higher number of root tubers per plant at the early bulking stage. The root tubers also attained the greater content of soluble sugar and starch. The high-yielding varieties formed root tubers earlier, showed strong abilities to transport photosynthates into the root tubers, and exhibited a higher mean accumulation rate. These varieties could also reduce the photosynthate consumption in branch leaves and stems. Therefore, the high-yielding varieties established growth advantage for the root tubers earlier. It contributed to a reasonable distribution structure of photosynthates that led to the high root tuber yield. Based on our results, effective agricultural measures can be chosen to improve the root tuber yield of sweet potato.

Response of Sweetpotato in Source-Sink Relationship Establishment, Expanding, and Balance to Nitrogen Application Rates

The pot, field mini-plot, and field split-plot experiments were carried out to investigate sweetpotato roots morphology(RM), number of tuberous roots per plant(NTR), leaf area index(LAI), shoots biomass, roots biomass and ratio of top to root(T/R-value) at 30, 60, 90, and 120 days after planting(DAP). At the whole growth period(0–120 d), nitrogen application promoted shoots growth, but had different effects on roots growth. At the early growth stage(0–30 d), low nitrogen rate(NR, N21) promoted roots growth and differentiation, but proper NR(N11, N22, N31) and excessive NR(N12, N23, N32) apparently inhibited roots development, causing NTR to decrease by 29.3%–36.6%(or 1.3–2.0 per plant)(P0.05). The NTR at different nitrogen rates tended to be same in the split-plot experiment after 60 DAP. At the middle growth stage(30–60 d), proper or excessive nitrogen rates were in favor of expansion of sweetpotato source-sink relationship(SSR), enhancing shoots biomass by 35.5%–48.9% and 73.4%–79.8%, respectively(P0.05), LAI rapidly ran up to four, but had no influence on roots biomass(P0.05). At the late growth stage(60–120 d), excessive NR sustained shoots biomass growth, LAI and T/R at harvest reached 4.9–5.6 and 1.50–1.51, respectively, which were apparently higher than those(3.3–3.5 and 0.58–0.64) under the proper NR(P0.05). When no nitrogen application, LAI and T/R at harvest were only 1.6–1.9 and 0.36–0.42, of which LAI was apparently lower than that under the proper NR(P0.05). At the same time, there was a difference in fresh weight of individual tuberous root(FWITR) under different nitrogen rates. FWITR(218–345 g) under the proper NR was higher than those under no NR(181–262 g) and excessive NR(160–285 g, P0.05), therefore, the final yield per plant under the proper NR(1.02–1.20 kg) was higher than that under no NR(0.88–0.91 kg) and excessive NR(0.79–0.87 kg, P0.05). It is showed that nitrogen as base fertilizer, its less or no application is favorable for the establishment of SSR, its proper or excessive application delays SSR at early growth stage, its right or excessive application promotes the expandation of SSR at middle growth stage, and only right application would keep SSR balance at late growth stage.

Rice Bran Affects Dry-matter Production of Chinese and Japanese Rice Cultivars

The effect of rice bran on dry matter production of different rice cultivars, namely the Chinese panicle weight types and Japanese panicle number types, was evaluated in field conditions, with growth, canopy production structure and the root system determined over a period of 60 days. The treatments consisted of rice cultivars with 1000 kg ha1 rice bran without agrochemicals (RB), cultivars with chemical fertilizer and cultivars with herbicide, with the latter serving as a control. The crop growth rate (CGR) and mean leaf area index (mLAI) in RB treatment were lower than that of the control; however, the net assimilation rate (NAR) was higher for all growth stages in this treatment. It was noted that CGR in RB and the control treatment depended greatly on mLAI during the early and middle growth stages, whereas CGR was more dependent on NAR in the late growth stage. Correlation between CGR in middle stage and the extinction coefficient of the canopy (k) at heading was apparent (p < 0.05). NAR in middle stage was positively correlated with mean leaf color and specific leaf weight (SLW). The correlations between NAR in the late stage and bleeding rate per number of primary roots, and per leaf area at maturity was apparent (p < 0.01). Root vitality and NAR were higher in RB treatment. The photosynthesis-related traits after heading in RB treatment were better than the control. Reduction of ∆W in RB treatment as well as the spikelets number (SN) was unapparent. The panicle number type cultivars did not inhibit growth during the early and middle growth stages with the presence of rice bran. The difference between growth, panicle number and weight cultivars was insignificant in the late stage. Discipline: Crop production Additional key words: bleeding rate, growth analysis, light extinction coefficient, the panicle number type cultivars, root system. This research was supported in part by Tianjin natural science fund for Scientific Research (No.11JCYBJC27100) from the Tianjin Municipal Science and Technology Commission, China. The Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No.46). This research was supported in part by the ScienceT accepted 2 March 2015 Introduction The use of nitrogen in paddy cultivation in China is three times higher than in Japan. In this context, excess application of chemical fertilizer in paddy cultivation pollutes the environment and has adverse effects on both aquatic and terrestrial organisms. The use of chemical fertilizers increases operation costs, resulting in higher rice and rice product prices. It is, therefore, important to find new alternatives as substitutes for chemical fertilizer in paddy farming to alleviate environmental issues arising from their use. Rice bran is often used in the organic paddy farming in Japan because of its efficacy as a fertilizer and herbicide. This cultivation technique fulfills the growing demand for agriculture products with fewer or no agrochemicals to

Root System Morphological and Physiological Characteristics of Indica-japonica Hybrid Rice of Yongyou Series

A field experiment was conducted to compare the root system morphological and physiological characteristics of four types of rice populations including indica-japonica hybrid rice of Yongyou series(A), japonica hybrid rice(B), conventional japonica rice(C), and indica hybrid rice(D) under high-yielding cultivation condition in the rice-wheat cropping system. Results were as follows:(1) The root dry weight, aboveground dry weight, number of root tips, root length, root surface area, root-shoot ratio and root volume of A were obviously higher than those of B, C, and D at the middle and late growth stage.(2) The proportion of number, length, surface area and volume of the adventitious roots(root diameter 0.3 mm) to the whole roots of A were higher than those of B and C, while lower than those of D at heading; the proportion of number, length, surface area and volume of the fine branches(root diameter ≤ 0.1 mm) and coarse branches(0.1 mm root diameter ≤ 0.3 mm) to total roots of A were higher than those of D, while lower than those of B and C at heading. The proportions of root weight in 0–5 cm, 5–10 cm, and 10–15 cm soil layers to total roots weight of A were higher than those of B and C, while lower than those of D; however, the proportions of root weight in 15–25 cm, 25–35 cm, 35–45 cm, and 45–55 cm soil layers to the total root weight where lower than those of B and C, while higher than these of D at heading.(3) The total absorbing surface area, active absorbing surface area, bleeding intensity, root oxidation activity, and root reducing activity of A were higher than those of B, C, and D. Compared with B, C, and D, the indica-japonica hybrid rice of Yongyou series had significant advantage in root-shoot coordination level, root amount, branch structure, root distribution in soil and biological activity in the middle and late growth stage. This peculiarity of A provides an important guarantee to realize the super-high-yield.

Effects of high magnetic field on the growth and magnetic properties of Fe-Ni nano-polycrystalline thin films with different thickness values

The Fe-Ni nano-polycrystalline thin films of 21 nm and 235 nm in thickness are prepared by molecular beam vapor deposition in the absence and the presence of a magnetic field as high as 6 T. The results show that in the absence of the magnetic field, the 21-nm-thick thin films are formed by the grain stacks, and the sizes of grains are about 6-7 nm. In the presence of 6 T, the 5-nm-thick flat layers of interconnected grains of 21-nm-thick thin films are first formed on the surfaces of the substrates, and the grains are then elongated along the surfaces of substrates. Later on, the 21-nm-thick thin films are formed by 6-7 nm-size-grain stacks. In the absence of the magnetic field, the average grain size of the 235-nm-thick thin film is 3.6 nm in the early growth stage, and it is 5.6 nm in the middle growth stage. The growth way of thin film is akin to columnar growth in the final growth stage, and the grains are elongated along the growth direction. In the presence of 6 T, the 5-nm-thick flat layers of interconnected grains of 235-nm-thick thin films are also formed on the surfaces of the substrates, and the grains are elongated along the surfaces of substrates. Later on, the 235-nm-thick thin films are formed by about 6.1-nm-size-grain stacks. Accordingly, the coercive forces in the out-of-plane and in the in-plane of thin films of different thickness values decrease by the 6 T magnetic field.

Study on nitrogen accumulation characteristics of peanuts in different texture soils

In this study, to adopt measures suiting local conditions, reasonable nutrition management and improve the yield of peanuts, the nitrogen absorption, accumulation and distribution characteristics of peanuts in different texture soils were investigated using box-planting methods. The results demonstrated that the times when the nitrogen accumulation of the root, stem and leaf of the peanuts in the sandy soil achieved the maximum value were earlier than those of the peanuts planted in the loam and clay. The nitrogen accumulations of the root, stem, leaf and seed exhibited that the nitrogen accumulation of the peanuts in the sandy soil was high at the early growth stage, that in the loam was high in the middle and late growth stages, and that in the clay was high in the late growth stage. The nitrogen accumulation of the peanuts in the mature period mainly existed in the reproductive body, accounting for 63.76–65.45%, and the accumulated nitrogen in the nutrients accounted for 34.55–36.24%. The accumulated nitrogen amount distributed in the reproductive body in different soils was clay > loam > sand, while the accumulated nitrogen amount distributed in the nutrients in different soils was sand > loam > clay, which was opposite to that of the accumulated nitrogen amount distributed in the reproductive body. The nitrogen of the peanut pods in the sand soil was mainly derived from the translocated amounts of the nitrogen accumulated in the root, stem and leaf, which accounted for a large proportion. The nitrogen of the peanut pods in the clay was mainly derived from the direct absorption by the roots, which accounted for a large proportion. The nitrogen of the peanut pods in loam was mainly derived from both the translocated and accumulated amounts of the nitrogen in the root, stem and leaf and the direct absorption by roots, which accounted for a moderate proportion.

Difference and Related Reason for Assimilate Distribution of Sweetpotato Varieties with Different Root Tuber Yields

A field experiment was conducted at agricultural experiment station of Shandong Agricultural University, Tai'an, Shandong Province in two growth seasons of 2011 and 2012. Six typical varieties of edible sweetpotato in North China were used, including Longshu 9, Hongxiangjiao, Taizhong 6, Sushu 8, Yizi 138, and Beijing 553, to study the difference and reason for assimilate distribution among varieties with different yield levels. The distribution characteristics of assimilate was studied by 13 C labeling during storage roots development; sucrose content of different stem parts and stem base diameter were measured as well. And the relationship between the above traits and harvest index, root tuber yield was also analyzed. The results showed that the root tuber yield of high-yielding varieties(Longshu 9, Hongxiangjiao, Taizhong 6, and Sushu 8) was about 60 t hm–2, whereas that of intermediate and low-yielding varieties(Yizi 138 and Beijing 553) was less than 50 t hm–2. And the harvest index of high-yielding varieties was significantly higher than that of intermediate and low-yielding varieties. The root tuber of high-yielding varieties became assimilate distribution center at early bulking stage, while for intermediate and low-yielding varieties that was at late bulking stage; and high-yielding varieties also had significantly higher 13 C distribution rate than that of intermediate and low-yielding varieties, indicating that high-yielding varieties had relatively higher ability to transport assimilate from functional leaves to root tubers. Sucrose content of stem base was higher than that of stem top, and the sucrose concentration gradient of intermediate and low-yielding varieties was higher than that of high-yielding varieties. Low-yielding varieties' stem base thickened faster than high-yielding varieties in the development of sweetpotato. The correlation analysis showed that root tuber yield had significantly positive correlation with harvest index(r = 0.98**, 2011; r = 0.93**, 2012). Root tuber yield and harvest index had significantly positive correlation with 13 C distribution rate of root tuber(0.87* and 0.91**, 2011; 0.92** and 0.99**, 2012); they also had significantly negative correlation with stem base diameter during middle and late growth stages(–0.78* and –0.83*; –0.88** and –0.95**). Therefore, high-yielding varieties got higher harvest index mainly due to less time taken by their root tuber to become assimilate distribution center and stronger ability of assimilate transportation from functional leaves to root tubers; and low-yielding varieties got lower abilities of assimilate transportation mainly because assimilate unloading in root tubers was not smoothly.

Performance evaluation study and hydrologic and productive analysis of irrigation systems at the Qazvin irrigation network (Iran)

The objective of this work is to develop a combined approach for performance evaluation of different irrigation practices based on the classical and neoclassical concept of irrigation efficiency, preliminary water accounting and water productivity. For this purpose, 2000ha of land under Qazvin irrigation network in Iran with various types of irrigation systems were selected. Classical irrigation efficiency for furrow irrigation system was found 5.9% and 27.8% in primary and middle growth stages, respectively. The lowest classical efficiency for sprinkler systems was for linear-move system (11.8% and 45.6% in primary and middle growth stages, respectively). The values of effective efficiency were less than net efficiency in all studied irrigation systems in both evaluation stages. Obtained results showed that effective efficiency could define irrigation management at farm scale, whereas net efficiency considered the concept of beneficial reuse at larger scales. The total beneficial fraction in all sprinkler irrigation systems was higher than in furrow irrigation system. Overall, the values of depleted beneficial fraction were lower for the furrow irrigation system, which was due to large deep percolation values. The maximum and minimum values of net water productivity were for the center pivot with height-regulated sprinklers (9652Rialsm−3) and furrow irrigation system (1391.4Rialsm−3).

The dynamic effects of pastures and crop on runoff and sediments reduction at loess slopes under simulated rainfall conditions

Ryegrass (Lolium perenne L.) and alfalfa (Medicago sativa L.) are widely-planted pastures, and spring wheat (Triticum aestivum L.) is one of the common crops on the Loess Plateau of China where serious erosion exists. However, their roles in regulating runoff and sediments have not been fully understood. This study investigated the effects of these vegetation types at various growth stages on reducing runoff and sediments in soil boxes under simulated rainfall conditions. Growth stages were set as: early stage (late May), middle stage (late June), and late stage (late July). Four indices were used to assess the capacity of reducing runoff and sediments in terms of runoff reduction benefit (RRB), sediment reduction benefit (SRB), ratio between runoff and sediment reduction (RRSR), and soil average/stable infiltration rate. The results showed that at the early and middle stages, RRB, SRB, RRSR, and soil average/stable infiltration rate were the largest for ryegrass followed by spring wheat and alfalfa. At the late stage, however, alfalfa following ryegrass performed better than spring wheat in reducing runoff and sediments. With the growth of vegetation, the capacity of ryegrass and alfalfa in reducing runoff and sediments increased. The RRB and SRB for the late-stage ryegrass were 69.5% and 98.6%, respectively, while they were 61.6% and 95.4% for the late-stage alfalfa, respectively. Spring wheat at middle stage performed best in reducing runoff and sediments over the whole growing period, with the RRB and SRB of 65.31% and 97.63%, respectively. In particular, the SRB for different vegetation types at all stages were over 90%, and were apparently higher than the RRB. In addition, the RRSR increased greatly from the early to middle growth stage for all vegetative treatments, indicating that the reduction in runoff was more effective than the reduction in sediment when vegetation grew mature. Since the majority of heavy rainstorms fall in the late growth stage (July–September) on the Loess Plateau, the functioning of artificial grass in reducing slope runoff and sediments should be stressed and investigated in further details.

Some Characteristics of Mechanically Transplanted Pot Seedlings in Super High Yielding Population of Indica-Japonica Hybrid Rice Yongyou 2640

In order to identify the characteristics of super high yielding population and its yield formation in mechanically transplanted pot seedlings of rice with wheat straw return, we selected a large panicle type indica-japonica hybrid rice Yongyou 2640 as material in Donghai, Xinghua and Hai'an, and analyzed grain yield and its components and characteristics of its super high yielding population(SHY 13.5 t ha–1) and high yielding population(HY 12.0 t ha–1). The results showed that, compared with HY SHY had more total population spikelets owing to its very significantly increased spikelets per panicle. There were no differences in effective panicle, percentage of filled grain and 1000-grain weight between SHY and HY treatments. SHY showed fewer tillers at the early growth stage, achieved expected number of stem and tiller at the critical leaf age for productive tiller, and had lower number of peak tiller at the jointing stage. Then, the number of population stems and tillers began to decrease slowly after jointing At maturity, the percentage of productive tiller in SHY was higher than that in HY. The leaf area index of SHY was lower than thaof HY at the critical leaf age for productive tiller and the jointing stage, the max leaf area index was about 8.5 at booting, which decreased stably after booting, and with the value above 3.5 at maturity. The dry matter accumulation of SHY was comparable to that of HY at the critical leaf age for productive tiller and at the jointing stage, increased greater after jointing, and was higher at booting, heading and maturity than that of HY. The ratio of total biomass accumulation was higher in SHY than in HY at the middle and late growth stage. The nitrogen accumulation, photosynthetic potential, crop growth rate and net assimilation rate were smaller at the early stage and higher at the middle and late stages in SHY. Therefore, SHY has greater photosynthate production and higher nitrogen accumulation than HY at the middle and late growth stage. In this study, we also discussed the key cultivation techniques for super-high-yielding production of pot seedling mechanical transplanting rice with wheat straw return.

Early growth stage water management effects on the fate of inorganic N, growth and yield in rice

Water and nitrogen (N) play vital roles in rice (Oryza sativa L.) production. Water-saving management decisions can influence soil conditions (oxidation and reduction), and these soil conditions affect the fate of N in paddy soil. We designed three irrigation regimes, namely, conventional irrigation (Flooding), shallow water depth (SWD), and a Non-flooding treatment, for our study. For the Flooding treatment, a ponding water depth of 0.05–0.06 m was maintained for 99 days after transplanting (DAT), and the water was drained 20 d before harvesting. For the SWD treatment, a ponding water depth of 0.01–0.02 m was maintained from 20 DAT to 99 DAT, and water was drained 20 d before harvesting. For the Non-flooding treatment, the plots were saturated (not flooded) from 20 to 57 DAT. After 57 DAT, a ponded water depth of 0.01–0.02 m was maintained until 99 DAT, and the water was drained 20 d before harvesting. The N fate and rice growth did not differ between the treatments during the early growth stages in response to the differences in water management. Rice root activity during the middle growth stage was higher for SWD, which was possibly because of the above-ground biomass and other factors during the middle growth stage of the rice. We found that the recovery efficiencies for N fertilizer, N uptake and above-ground biomass at the heading stage were higher for SWD than for the other two treatments. Although the soil status (reduction or aerobic conditions) was the same for the different water treatments up to the maximum tiller number stage, either the SWD or Non-flooding option could be used to conserve water. In addition, the fate of the N fertilizer, the N use efficiency, the rice growth and the rice yield were the same or higher with these two treatments than with the Flooding water management treatment.

The growth and characterization of GaN films on cone-shaped patterned sapphire by MOCVD

GaN films are grown on cone-shaped patterned sapphire substrates (CPSSs) by metal-organic chemical vapor deposition, and the influence of the temperature during the middle stage of GaN growth on the threading dislocation (TD) density of GaN is investigated. High-resolution X-ray diffraction (XRD) and cathode-luminescence (CL) were used to characterize the GaN films. The XRD results showed that the edge-type dislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates (CSSs). Furthermore, when the growth temperature in the middle stage of GaN grown on CPSS decreases, the full width at half maximum of the asymmetry (102) plane of GaN is reduced. This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs. The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS, and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases.

Comparison of six evapotranspiration models for a surface irrigated maize agro-ecosystem in Northern Italy

The approaches for the estimation of evapotranspiration (ET) can be classified in “direct” methods, based on the original Penman–Monteith (PM) equation, in which the canopy resistance rc is modelled, and “indirect” methods, based on the preliminary calculation of ET for a well-watered reference grass (ETo) with a constant rc, which is then multiplied by a crop coefficient Kc to obtain ET. Even if the latter approaches are more widely adopted for their practical simplicity, many authors show that the former often provide better ET estimates in absence of calibration of crop parameters. In this study the performances of different direct and indirect methods were evaluated in the case of a surface irrigated maize grown in the Padana Plain (Northern Italy). The “one-layer” original PM equation with three different models for rc (Monteith, Jarvis, Katerji–Perrier), the “two-layers” PM model proposed by Shuttleworth and Wallace, the “single” and “double crop coefficient” models illustrated in the Paper FAO-56 were compared to latent heat fluxes measured in 2006 by eddy-covariance techniques. Results confirm that direct methods are more performing. The FAO-56 models with generalized crop coefficients overestimate ET, especially during the middle growth stage.

Evapotranspiration models for a maize agro-ecosystem in irrigated and rainfed conditions

A high level of accuracy in the estimation of crop evapotranspiration (ET) may lead to significant savings of economic and water resources in irrigated agriculture. Although ET is a fundamental process in many applications, it cannot be directly measured but it has to be estimated by monitoring the exchange of energy/water above the vegetated surface (micrometeorological methods), or as a residual term of the hydrological balance (lysimeters, soil water budget). The techniques to be adopted are often complex, costly and require specific equipment. Thus, since the ‘50s, many researchers have devoted their activity to the development of models for its estimation. The available approaches can be classified in “direct” methods, based on the original Penman-Monteith (PM) equation, in which the canopy resistance rc is modelled, and “indirect” methods, based on the preliminary calculation of ET for a well-watered reference grass (ET0) with a constant rc, which is then multiplied by a crop coefficient Kc and, in case, by a stress coefficient Ks to obtain ET. Even if the latter approaches are more widely adopted for their practical simplicity, many authors show that the former often provide better ET estimates in absence of calibration of crop parameters. In this study the performances of different direct and indirect methods were evaluated in the case of a surface irrigated and of a rainfed maize grown in the Padana Plain (Northern Italy). The following models were considered: the “one-layer” original PM equation with three different models for rc (Monteith, Jarvis, Katerji-Perrier), the “two-layers” PM model proposed by Shuttleworth and Wallace, the “single” and “double” crop coefficient models illustrated in the Paper FAO-56. Latent heat fluxes measured in 2006 and 2011 in an experimental maize field by eddy-covariance were used to evaluate the models accuracy. Crop, soil and meteo data monitored contextually were used for the implementation of the different models. Results confirm that direct methods are more performing for both irrigated (2006) and rainfed (2011) conditions, with the SW model providing the best results and the FAO-56 models with generalized crop coefficients overestimating ET, especially during the middle growth stage.

Effect of Limited Water Supply on Crop Growth of Spring Maize (&lt;i&gt;Zea Mays&lt;/i&gt;)

An experiment was conducted to determine the effect of limited water supply on plant height, leaf area, dry matter and net assimilation rate (NAR) of spring maize. The results indicated that limited water supply had little effect on plant height of maize at six-leaf, twelve-leaf, heading and early grain filling except the end of filling. Leaf growth and leaf area expansion were effectively increased at middle and late maize growth stages under limited water supply and the maximum leaf area was maintained at early grain filling to middle filling. In addition, dry matter accumulation of maize in reproductive organs may be promoted by limited water supply. Finally, limited water supply also had great effect on net assimilation rate of maize and the maximum was maintained at six-leaf to twelve-leaf, followed by heading to silking.

RETRACTED ARTICLE: Effect of calcium and silicate application on pathogenicity of Erwinia carotovora subsp. carotovora in Zantedeschia spp.

The purpose of this study was to evaluate the effects of calcium and silicate on plant growth and resistance to Erwinia carotovora subsp. carotovora in Zantedeschia aethiopica ‘Childsiana’. Calcium and silicate as basal fertilizer (mixed with soil before cultivation) were applied at 0, 100, 200, or 400 kg·10 a−1, respectively. Potassium silicate (K2O·nSiO2) and CaCl2 foliar application were applied 3 times every 2 weeks at 0, 0.05, 0.1, or 0.2%, respectively at the middle stage of growth on the Zantedeschia. The level of resistant to Erwinia carotovora subsp. carotovora was tested by leaf disk test at blooming stage. The higher concentration of calcium and silicate in the foliar application and basal application resulted in vigorous leaf growth, hardness of petiole and flower stalk and in fresh weight. The resistance to Erwinia carotovora subsp. carotovora was more effective in CaCl2 foliar treatment than the basal fertilization treatment. Foliar treatment at 0.2% CaCl2 was the most effective against the resistance of Erwinia carotovara subsp. carotovora. Also, the level of resistant to Erwinia carotovora subsp. carotovora was higher in proportion to the silicate application rate both in foliar and basal application of fertilizer. In the analysis of SEM, it was observed that at high concentration of silicate there was more accumulates of Si between cell wall, vascular bundle, and companion cell around sieve tube element. It was consistent with the result of hardness of petiole and flower stalk.

Reconstruction of the Growth History of a Large Synthesized Diamond Crystal by Synchrotron Topography

The growth history of a large diamond crystal synthesized by HPHT temperature gradient method was reconstructed by the defects features in the crystal. The crystal defects were revealed using white synchrotron radiation topography. Dislocations originated from the surfaces of the seed and extended along the directions of &lt;100&gt; were observed within the crystal grown at the early stage. The crystal was then grown to the [00-direction at the middle growing stage and no dislocations were generated at this stage. A lot of dislocation bundles were generated at the last growth stage of the crystal and each bundle was composed of several straight extended dislocations originated from the same point and extended radially within a sector of about thirty degrees centigrade. The origins of the dislocation bundles were distributed near the surface of the crystal. Most of the dislocation bundles were generated near the (-100), (010) and (00-1) and extended to the [-10, [01 and [00-, approximately. The generation of the dislocation bundles was caused by the rapid descent of the temperature in the last growth stage of the diamond crystal.