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21.
The intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems in the North China Plain (NCP) rely on the heavy use of mineral nitrogen (N) fertilizers. As the fertigated area of wheat and maize in the NCP has grown rapidly during recent years, developing N management strategies is required for sustainable wheat and maize production. Field experiments were conducted in Hebei Province during three consecutive growth seasons in 2012–2015 to assess the influence of different N fertigation rates on N uptake, yield, and nitrogen use efficiency [NUE: recovery efficiency (REN) and agronomic efficiency (AEN)]. Five levels of N application, 0 (FN0), 40 (FN40%), 70 (FN70%), 100 (FN100%), and 130% (FN130%) of the farmer practice rate (FP: 250 kg N ha?1 and 205.5 kg N ha?1 for wheat and maize, respectively), corresponding to 0, 182.2, 318.9, 455.5, and 592.2 kg N ha?1 y?1, respectively, were tested. Nitrogen in the form of urea was dissolved in irrigation water and split into six and four applications for wheat and maize, respectively. In addition, the treatment “drip irrigation + 100% N conventional broadcasting” (DN100%) was also conducted. All treatments were arranged in a randomized complete block design with three replications. The results revealed the significant influence of both N fertigation rate and N application method on grain yield and NUE. Compared to DN100%, FN100% significantly increased the 3‐year averaged N recovery efficiency (REN) by 0.09 kg kg?1 and 0.04 kg kg?1, and the 3‐year averaged N agronomic efficiency (AEN) by 2.43 kg kg?1 and 1.62 kg kg?1 for wheat and maize, respectively. Among N fertigation rates, there was no significant increase in grain yield in response to N applied at a greater rate than 70% of FP due to excess N accumulation in vegetative tissues. Compared to FN70%, FN100%, and FN130%, FN40% increased the REN by 0.17–0.57 kg kg?1 and 0.03–0.34 kg kg?1and the AEN by 4.60–27.56 kg kg?1 and 2.40–10.62 kg kg?1 for wheat and maize, respectively. Based on a linear‐response relationship between the N fertigation rate and grain yield over three rotational periods it can be concluded that recommended N rates under drip fertigation with optimum split applications can be reduced to 46% (114.6 kg N ha?1) and 58% (116.6 kg N ha?1) of FP for wheat and maize, respectively, without negatively affecting grain yield, thereby increasing NUE.  相似文献   
22.
In this study, the ADAPT (Agricultural Drainage and Pesticide Transport) model was calibrated and validated for monthly flow and nitrate-N losses, for the 2000-2004 period, from two minor agricultural watersheds in Seven Mile Creek (SMC-1 and SMC-2) in south-central Minnesota. First, the model was calibrated and validated using the water quality data from the SMC-1 and again independently validated with the SMC-2 dataset. The predicted monthly flow and associated nitrate-N losses agreed reasonably with the measured trends for both calibration (r2 = 0.81 and 0.70 for flow and nitrate-N losses, respectively) and validation (r2 = 0.85 and 0.78 for flow and nitrate-N losses from SMC-1, and 0.89 and 0.78 for flow and nitrate-N losses from SMC-2, respectively) periods. The model performed less satisfactorily for the snowmelt periods than it did for the entire simulation period. Using the calibrated model, long-term simulations were performed using climatic data from 1955 to 2004 to evaluate the effects of climatic variability and N application rates and timing on nitrate-N losses. The predicted nitrate-N losses were sensitive to N application rates and timing. A decrease in the fall N application rate from 179.3 to 112 kg/ha decreased nitrate-N losses by 23%. By changing application timing from fall to spring at a rate of 112 N kg/ha, nitrate-N losses decreased by 12%. The predicted nitrate-N losses showed a linear response to precipitation with larger losses generally associated with wet years. A 25% increase in mean annual precipitation would offset reductions in nitrate-N loss achieved using better N fertilizer management strategies described above.  相似文献   
23.
Production of Eruca-Brassica Hybrids by Embryo Rescue   总被引:3,自引:0,他引:3  
Allied species of crop Brassicas have potential value as donors of useful nuclear/organelle genomes. Eruca sativa, a member of subtribe Brassicineae, is resistant to white rust and well adapted to drought. Attempts to hybridize it with Brassica campestris by conventional methods were unsuccessful. However, hybrids were obtained by embryo rescue and the hybrid embryos were found to produce numerous secondary embryos in upto 7 to 8 subcultures. Plantlets developed from them exhibited morphological characteristics of both parents. The chromosome number of 2n = 42 showed that they were amphidiploids. The plants were allotctraploids (2n = 42) and showed 21 bivalents at M1 of meiosis. Hybridization of total DNA of the hybrids with two probes, a B. campestris tandem repeat DNA and 18s ribosomal DNA of wheat showed that it was derived from the genome of both parents. The hybrids are self-fertile and show the same high fertility even in A3 generation. They were selfed or crossed with B. juncea, B. campestris and B. nigra to screen for useful agronomical traits. Six more embryos of E. saliva × B. campestris have been obtained and their growth is being studied. Preliminary small scale field trials indicate that the selfed hybrid is comparable in yield with a high yielding commercial variety of B. juncea.  相似文献   
24.
Arbuscular mycorrhizal (AM) fungi display efficient association with the land plants and is known to protect plants against various abiotic stresses including heavy metal stress. This work reports the synergistic effects of natural genotypic variation and AM association in cadmium (Cd) stress alleviation. Two genotypes of wheat viz. RAJ 4161 (resistant) and PBW 343 (sensitive) were subjected to different concentrations of Cd (0, 100, 200 and 300 mg Cd kg?1 soil) for 30 days. Cd application resulted in increased lipid peroxidation and decreased plant growth. However, AM inoculated RAJ 4161 displayed significantly higher ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) activity and calcium (Ca), iron (Fe)and zinc (Zn) concentration in plants. The coordination of increased antioxidant activity and high nutrient content in RAJ 4161 indicated better protective mechanism as compared to PBW 343.  相似文献   
25.
To examine tolerance of cadmium (Cd) by eggplant (Solanum melongena L.) cv. ‘Hybrid PK 123’, plants were grown in refined sand in complete nutrient solution for 52 days in a glasshouse at ambient temperature. Cadmium sulfate was superimposed on day 53, at variable levels: nil, 0.05, 0.1, 0.2, 0.4, and 0.5 mM. Influence of excess Cd was discernible after 5 days of metal supply at 0.4 and 0.5 mM Cd as depression in growth. At these levels, foliar symptoms were initiated as paling of young leaves at the base progressing upward. With increase in age, affected leaves turned golden yellow and these effects spread to lower leaves. Leaf size and floral initiation were very much restricted. These types of phenotypes induced leaf senescence. Excess Cd reduced the biomass and fruit yield of plants. At higher levels (>0.1 mM) of Cd, fruit formation was completely inhibited and fruits formed at 0.05 and 0.1 mM Cd were smaller in size. Besides this, excess Cd disturbed the metabolism of eggplant by reducing the concentration of chlorophyll (a and b), protein, Hill reaction activity, and activity of antioxidant enzymes—catalase and ascorbate peroxidase; whereas the activity of peroxidase and ribonuclease increased in leaves of eggplant. Cadmium excess reduced the concentration of Fe and Zn and Cd increased that of proline, lipid peroxidation, phenols, reducing sugars and Cd concentration in leaves of eggplant.  相似文献   
26.
Rice blast, caused by fungus Magnaporthe grisea, is a serious disease causing considerable economic damage worldwide. Best way to overcome disease is to breed for disease‐resistant cultivars/parental lines of hybrids. Pusa RH10, first aromatic, fine‐grain rice hybrid released and cultivated extensively in India. Hybrid and its parental lines, Pusa 6A and PRR78, are highly susceptible to blast. CO39 pyramid carrying two dominant, broad‐spectrum blast‐resistance genes, viz. Pi‐1 and Piz‐5, used as a donor parent to introgress these genes into PRR78 using marker‐assisted backcrossing (MABC). Microsatellite markers RM5926 and AP5659‐5 tightly linked to Pi‐1 and Piz‐5 genes, respectively, were used for foreground selection to derive introgression lines. Further, these lines were evaluated for agronomic performance, disease reaction and cooking quality traits along with PRR78. Most of the improved lines were on par with PRR78 for all traits evaluated except gelatinization temperature. Recurrent parent genome percentage (RPG) study also revealed similarity of these lines with PRR78. Hybrids derived using improved PRR78 lines were superior over Pusa RH10 in terms of yield.  相似文献   
27.
Mahsuri a popular traditional variety and the first rain-fed mega variety of the Indian sub- continent. It is highly susceptible to bacterial leaf blight caused by Xanthomonas oryzae pv.oryzae. Nine best performing families of Mahsuri pyramid containing four bacterial blight resistance genes (Xa4, xa5, xa13 and Xa21) were evaluated for agronomic, yield and its related characters viz. days to 50% flowering, plant height, number of tillers, panicle length, filled grains per panicle, grain weight, and yield under natural and disease pressure conditions for three consecutive wet seasons. In addition these pyramids were also evaluated for three different spacings to find out the optimum spacing under disease free and disease pressure conditions. Results revealed that under disease free conditions there was no significant difference between the pyramids and the parent for the characters evaluated in each spacing. However characters plant height, number of tillers, panicle length, filled grains per panicle, yield per plant and yield per sq. m. showed significant variation between the different spacings across seasons. Under heavy disease pressure the parent exhibited highly susceptible reaction whereas the pyramid families were highly resistant. A wider spacing had less yield loss when compared to dense planting under BB infestation in case of parent. There was no such yield loss in the pyramid families. When yield per sq. m. was taken into consideration the 20 × 20 cm spacing showed the highest yield when compared to the other two spacings since number of plants were more. The pyramids insulated the yield loss against bacterial leaf blight and are a gain to the farmers to help overcome the heavy yield losses due to this disease. These pyramids have the potential to replace the parent and can be used directly. In addition they can be used as donors for bacterial blight resistance in any breeding program.  相似文献   
28.
The complete coat protein (cp) gene sequence of eighty Tomato leaf curl New Delhi virus-[potato] (ToLCNDV-[potato]) isolates collected from eleven states were determined. Phylogenetic analysis based on cp gene grouped the isolates into two major clades (I & II) and they shared 95.9–100.0% identity. The DNA A and DNA B of eight representative isolates (six from clade I and two from clade II) were 2739–2740 and 2692–2694 nts long and shared 94.6–99.4% and 97.2–99.5% homology within the isolates, respectively. Among the eight isolates, the DNA A of two isolates (Clade II), GWA-5 and FAI-19 had 94.6–95.3% sequence identity to other six isolates and formed a sub-clade within the ToLCNDV-[potato] isolates. Similar grouping was also revealed with AC1 and AC4 genes of these eight isolates. The DNA A components shared more than 90.0% identity with the DNA A of ToLCNDV isolates from cucurbitaceous crops, tomato, bhendi, 89.0–90.0% with ToLCNDV-papaya isolates and 70.4–74.0% with other tomato leaf curl viruses. Hence, the begomovirus infecting potatoes are the ToLCNDV isolates, designated as ToLCNDV-[potato]. Whereas, the DNA B components shared 86.6–91.7% identity with ToLCNDV isolates from cucurbits, tomato and bhendi. Evidence for intra-species recombination was detected only in DNA A with a maximum of three events in GWA-5 and FAI-19 isolates. Analysis of cp gene, DNA A, iterons and recombination events clearly indicate that two groups of ToLCNDV-[potato] infects potato in India.  相似文献   
29.
北方旱区保护性耕作对农田土壤水分的影响   总被引:22,自引:10,他引:12  
土壤水分是中国北方旱区农业生产的主要限制因子,研究保护性耕作技术体系下土壤水分的动态变化,明确不同耕作模式下的水分平衡规律,对于选择适宜的保护性耕作技术,提高北方旱区土壤水分的利用效率具有重要的指导意义。该文在2a田间试验的基础上采用DSSAT模型对4个不同保护性耕作处理的土壤体积含水量、水分平衡以及水分利用效率进行了模拟和检验。结果表明干旱年份保护性耕作处理土壤体积含水量较传统耕作高,RMSE误差在0.025~0.063;干旱年份传统耕作土壤储水量减少最多,为144.6mm,降水较多年份减少也最多,为46.1mm;干旱年份水分利用效率1.52~1.78kg/m3,免耕覆盖水分利用效率最高,降水较多年份水分利用效率1.70~1.71kg/m3,各处理间差异并不显著。研究结果为保护性耕作技术对农田土壤水分的影响研究提供了理论依据。  相似文献   
30.
A commercially developed cytokinin and seaweed extract formulation “Dravya” was used at 0.3% concentration for soaking of sorghum seeds for 12 h to test its effect on germination, vigour index, chlorophyll content and defense enzyme activity against seed mycoflora of sorghum. Among the treatments, Dravya (0.3%) with Dithane M-45 (0.1%) and GLSTIN (0.1%) or separately or in combination resulted is maximum percentage of seed germination, seedling vigour and reduced the incidence of seed mycoflora besides defense enzymes enhancement was noticed. In this study, Dravya was used for seed soaking, foliar spray, separately as well as in combination with GLSTIN and Mancozeb M-45 to test its efficacy in the enhancement of seedling vigour, chlorophyll content and defence enzyme activities. Hence, it is inferred that Dravya is a good growth promoter and improves natural resistance to disease in sorghum.  相似文献   
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