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1.
Effects of N-deficiency and timing of N supply on the recovery and distribution of labeled 15N in contrasting maize hybrids 总被引:3,自引:0,他引:3
Little information exists on the pattern of nitrogen (N) uptake, remobilization and N use efficiency (NUE) in Leafy and stay-green (SG) maize (Zea mays L.) genotypes. A pot experiment was conducted under controlled nutrition and growing conditions to determine the response of Leafy and SG maize genotypes to different levels of N-deficiency and timing of N supply. Three contrasting maize hybrids, Pioneer 3905 (a conventional hybrid with moderate SG characteristics), Pioneer 39F06 Bt (with a high score of SG trait) and Maizex LF850-RR (with a Leafy trait) were grown in 6 L plastic pots. Five different N treatments [no supply of N until V8 (N1), no supply of N after V8 (N2), no supply of N after silking (N3), no supply of N beyond 3 weeks after silking (N4), and continuous N supply from emergence to physiological maturity (N5; standard check)] were imposed through modified Hoagland solution applied manually. Labeled 15N of 5% 15N2–NH4NO3fertilizer was applied at 3 g per pot at the start of each schedule N treatment. Total amounts of N applied in different treatments were 3.13, 1.32, 1.90, 2.63 and 3.40 g, respectively in N1, N2, N3, N4 and N5. Dry matter, N concentration, 15N (atom% enrichment) and NUE were determined in roots, stalk, leaves and grains at crop maturity. The three contrasting hybrids did not differ in grain yield, total N acquisition, partitioning of 15N and NUE. Restriction of N supply until V8, and from V8 to physiological maturity significantly reduced grain yield and N-uptake in all hybrids. Irrespective of the level of N-deficiency in plant and timing when the labeled fertilizer was applied, the amount of 15N recovered in the matured plant was the same in all N treatments. It has been evident that maize continued to take up N beyond 3 weeks after silking and the later N was applied during the development, the higher proportion of it was partitioned to grains. Of the total 15N uptake, 78% was partitioned to kernels in the N4 treatment compared to only 61% in the control. Our data showed no evidence of differential N uptake, remobilization and NUE in the SG or Leafy hybrids tested, but the timing of N application and level of N-deficiency in plant significantly influenced N uptake, remobilization and N-dynamics in maize. 相似文献
2.
Composts are considered low analysis fertilizers because their nitrogen and phosphorus content are around 1% and the organic nitrogen mineralization rate is near 10%. If compost is added to agricultural land at the N requirement of grain crops (40 – 100 kg N ha–1), application rates approach 40–100 mg ha–1. Much lower rates may be advisable to avoid rapid accumulation of growth limiting constituents such as heavy metals found in some composts. Combining low amendment rates of composts with sufficient fertilizer to meet crop requirements is an appealing alternative which (a) utilizes composts at lower rates than those needed to supply all the crop N requirement, (b) reduces the amount of inorganic fertilizer applied to soils, and (c) reduces the accumulation of non-nutrient compost constituents in soils. A study was conducted to compare the effects of blends of biosolids compost (C) with 15N urea(U) or 15NH4 15NO3 (N) fertilizers to fertilizer alone on tall fescue (Festuca arundinacea L.) growth and N uptake. Blends which provided 0, 20, 40 or 60 mg N kg–1 application rate as compost N and 120, 100, 80 or 60 mg N kg–1 as fertilizer N, respectively, were added to Sassafras soil (Typic Hapludults). Fescue was grown on the blends in a growth chamber for 98 days. Fescue yields recorded by clippings taken at 23, 46 and 98 days and roots harvested after the 98-day clipping increased with increasing fertilizer level for both NH4NO3 and urea and with or without compost. Nitrogen uptake by fescue responded similarly to yield with increases recorded with increasing fertilizer levels with or without compost. Paired comparisons based on cumulative 98-day clippings data showed that yields from blends were equal to yields from fertilizer treatments containing the same percentage of fertilizer as the blends. These data indicated that compost did not provide sufficient plant-available N to increase yields or N uptake. None of the blends equaled 120 mg N kg–1 fertilizer rate except for 100 mg NH4NO3-or urea-N kg–1 –20 mg compost-N kg–1blends. The data suggest that biosolids compost blended with fertilizer at a rate of 2–6 mg ha –1 did not supply sufficient additional available N to increase yields or N uptake over those of fertilizer alone. 相似文献
3.
Grain yield, symbiotic N2 fixation and interspecific competition for inorganic N in pea-barley intercrops 总被引:4,自引:0,他引:4
Erik Steen Jensen 《Plant and Soil》1996,182(1):25-38
The effect of mixed intercropping of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.), compared to monocrop cultivation, on the yield and crop-N dynamics was studied in a 4-yr field experiment using 15N-isotope dilution technique. Crops were grown with or without the supply of 5 g 15N-labeled N m-2. The effect of intercropping on the dry matter and N yields, competition for inorganic N among the intercrop components, symbiotic fixation in pea and N transfer from pea to barley were determined. As an average of four years the grain yields were similar in monocropped pea, monocropped and fertilized barley and the intercrop without N fertilizer supply. Nitrogen fertilization did not influence the intercrop yield, but decreased the proportion of pea in the yield. Relative yield totals (RYT) showed that the environmental sources for plant growth were used from 12 to 31% more efficiently by the intercrop than by the monocrops, and N fertilization decreased RYT-values. Intercrop yields were less stable than monocrop barley yields, but more stable than the yield of monocropped pea. Barley competed strongly for soil and fertilizer N in the intercrop, and was up to 30 times more competitive than pea for inorganic N. Consequently, barley obtained a more than proportionate share of the inorganic N in the intercrop. At maturity the total recovery of fertilizer N was not significantly different between crops, averaging 65% of the supplied N. The fertilizer N recovered in pea constituted only 9% of total fertilizer-N recovery in the intercrop. The amount of symbiotic N2 fixation in the intercrop was less than expected from its composition and the fixation in monocrop. This indicates that the competition from barley had a negative effect on the fixation, perhaps via shading. At maturity, the average amount of N2 fixation was 17.7 g N m-2 in the monocrop and 5.1 g N m-2 in the intercropped pea. A higher proportion of total N in pea was derived from N2 fixation in the intercrop than in the monocrop, on average 82% and 62%, respectively. The 15N enrichment of intercropped barley tended to be slightly lower than of monocropped barley, although not significantly. Consequently, there was no evidence for pea N being transferred to barley. The intercropping advantage in the pea-barley intercrop is mainly due to the complimentary use of soil inorganic and atmospheric N sources by the intercrop components, resulting in reduced competition for inorganic N, rather than a facilitative effect, in which symbiotically fixed N2 is made available to barley.Abbreviations MC
monocrop
- IC
intercrop
- PMC
pea monocrop
- BMC
barley monocrop
- PIC
pea in intercrop
- BIC
barley in intercrop 相似文献
4.
Summary Field experiments were conducted to determine the effects of the amount, time and method of fertilizer N application on the
efficiency of N uptake, N2 fixatio and yield of soybean.
Soil and foliar fertilizer N, applied during the pod-filling stage were absorbed by plants with equal and high efficiency,
compared to an appreciably lower utilization efficiency for N applied before seedling emergence. These results reveal that
the soybean roots were active in N uptake during these late stages of growth. Nitrogen fertilization during pod-filling resulted
in significant yield increases over the control treatment which received an early application of 20 Kg N/ha. Seed yield increases
were, however, more pronounced than total dry matter yield, and virtually all of the late-applied N was translocated into
the pods. Nitrogen fixation in soybean was not influenced by the application of 40 kg N/ha to plants as soil or foliar N during
the pod-filling stage. However, 80 kg N/ha supplied during pod-filling as 40 kg soil plus 40 kg foliar N/ha significantly
reduced the amount of N2 fixed.
The results obtained in these studies suggest that inadequate N supply during pod-filling limited soybean yields, and that
by the judicious application of fertilizer N during the late stages of growth, it was possible to enhance soybean yields without
necessarily inhibiting N2 fixation. 相似文献
5.
Nitrogen mineralization and potential nitrification at different depths in acid forest soils 总被引:2,自引:0,他引:2
Yield decline of cereals grown in monoculture may be alleviated with alternative crop management strategies. Crop rotation and optimized tillage and fertilizer management can contribute to more sustainable food and fiber production in the long-term by increasing diversity, maintaining soil organic matter (SOM), and reducing adverse effects of excessive N application on water quality. We investigated the effects of crop sequence, tillage, and N fertilization on long-term grain production on an alluvial, silty clay loam soil in southcentral Texas. Crop sequences consisted of monoculture sorghum (Sorghum bicolor (L.) Moench,) wheat (Triticum aestivum L.), and soybean (Glycine max (L.) Merr), wheat/soybean double-crop, and rotation of sorghum with wheat/soybean. Grain yields tended to be lower with no tillage (NT) than with conventional tillage (CT) early in the study and became more similar after 11 years. Nitrogen fertilizer required to produce 95% to maximum sorghum yield was similar for monoculture and rotation upon initiation of the experiment and averaged 16 and 11 mg N g-1 grain with NT and CT, respectively. After 11 years, however, the N fertilizer requirement became similar for both tillage regimes, but was greater in monoculture (17 mg N g-1 grain) than in rotation (12 mg N g-1 grain). Crop sequences with double-cropping resulted in greater land use efficiency because similar or lower amounts of N fertilizer were required to produce equivalent grain than with less intensive monoculture systems. These more intensive crop sequences produced more stover with higher N quality primarily due to the inclusion of soybean in the rotation. Large quantities of stover that remained on the soil surface with NT led to greater SOM content, which increased the internal cycling of nutrients in this soil. In southcentral Texas, where rainfall averages nearly 1000 mm yr-1, more intensive cropping of sorghum, wheat, and soybean with moderate N fertilization using reduced tillage can increase grain production and potentially decrease N losses to the environment by cycling more N into the crop-SOM system. 相似文献
6.
This study was conducted to investigate the influence of soil water potential, depth of N placement, timing, and cultivar on uptake of a small dose of labeled N applied after anthesis by wheat (Triticum aestivum L.) Understanding postanthesis N accumulation should allow better control of grain protein concentration through proper manipulation of inputs. Two hard, red spring-wheat cultivars were planted in early and late fall each yr of a 2-yr field experiment. Less than 1 kg N ha–1 as K 15NO3 was injected into the soil at two depths: shallow (0.05 to 0.08 m) and deep (0.15 to 0.18 m). In both years an irrigation was applied at anthesis, and injections of labeled N were timed 4, 12, and 20 days after anthesis (DAA). Soil water potential was estimated at the time of injection. Mean recovery of 15N in grain and straw was 57% of the 15N applied. Recovery did not differ between the high-protein (Yecora Rojo) and the low-protein (Anza or Yolo) cultivars. Mean recovery from deep placement was 60% versus only 54% from shallow placement (p < 0.01). Delaying the time of injection decreased mean recovery significantly from 58% at 4 DAA to 54% at 20 DAA. This decrease was most pronounced in the shallow placement, where soil drying was most severe. Regressions of recovery on soil water potential of individual cultivar x yr x planting x depth treatments were significant only under the driest conditions. Stepwise regression of 15N recovery on soil water potential and yield parameters using data from all treatments of both years resulted in an equation including soil water potential and N yield, with a multiple correlation coefficient of 0.64. The translocation of 15N to grain was higher (0.89) than the nitrogen harvest index (0.69), and showed a highly significant increase with increase in DAA. This experiment indicates that the N uptake capacity of wheat remains reasonably constant between 4 and 20 DAA unless soil drying is severe. 相似文献
7.
A pot experiment was conducted to determine the effects of the application of 13C (1.256 atom%) and 15N (1.098 atom%) dual-labeled maize residue compost (MRC) on the nitrogen and carbon uptake by radish, komatsuna, and chingensai
as compared with the effect of inorganic fertilizer (IF). The vegetables were grown over three consecutive growing seasons
over 4 months; compost was applied at the rate of 24 g kg–1 soil. Nonlabeled nitrogen fertilizer was applied to the compost treatments in the second and third crops to compare the effects
of blends of compost with N fertilizer to fertilizer alone. The N uptake and yield of vegetables were significantly higher
with the recommended inorganic N treatment. The vegetables took up significantly (P < 0.05) lower amounts of N from MRC than from IFs during the three cultivations. The values of the N uptake derived by fertilizer
application to the plant exhibited significant differences among different vegetables. Nitrogen recovered by komatsuna and
chingensai from MRC was 7.3 (6.6%), 2.7 (1.8%), and 2.3, (1.7%) in the first, second, and third crops, respectively. Radish,
komatsuna, and chingensai recovered significant amounts of C from MRC in the first and second crops, with negligible C recovery
in the third crop. The initial loss of fertilizer C in soil at the first crop indicates that the microbial decomposition decoupled
substantial amounts of 13C/15N-labeled compounds early in plant development, thus giving the microorganisms a preemptive competitive advantage in the acquisition
of easily available 13C/15N-labeled substrates. It is concluded that a combination of compost and inorganic N did not supply sufficient plant-available
N to increase vegetables yields or N uptake over those of fertilizer alone. The data suggested that higher productivity of
vegetables might be achieved after the accumulation of a certain amount of residual compost N. 相似文献
8.
The dynamics of biomass and N accumulation following defoliation of alfalfa and the application of N fertilization has rarely been studied under field conditions, particularly in the seeding year. Our objectives were to determine the effect of N fertilization on the dynamics of biomass and N accumulation during the first regrowth of alfalfa in the seeding year, and to determine if a model describing critical N concentration developed for established stands could be used in the seeding year. In two separate experiments conducted in 1992 and 1993, the biomass and N accumulation of alfalfa grown with three N rates (0, 40 and 80 kg N ha-1) were determined weekly. Maximum shoot growth was reached with 40 kg N ha-1 in 1992, and maximum shoot growth was not reached with the highest N fertilization rate in 1993. Nitrogen fixation, root N reserves and soil inorganic N uptake when no N was applied were, therefore, not sufficient to ensure non-limiting N conditions, particularly when growth rates were the highest between 14 to 21 d after defoliation. Nitrogen fertilization increased shoot biomass accumulation in the first 21 d of regrowth, biomass partitioning to the shoots and shoot and taproot N concentrations. The model parameters of critical N concentration developed by Lemaire et al. (1985) for established stands of alfalfa were not adequate in the seeding year. The N requirements per unit of shoot biomass produced are greater in the seeding year than on established stands, and this was attributed to a greater proportion of leaves in the seeding year. 相似文献
9.
In the tropics, cowpea is often intercropped with maize. Little is known about the effect of the intercropped maize on N2-fixation by cowpea or how intercropping affects nitrogen fertilizer use effiency or soil N-uptake of both crops. Cowpea and maize were grown as a monocrop at row spacings of 40, 50, 60, 80, and 120 cm and intercropped at row spacing of 40, 50, and 60 cm. Plots were fertilized with 50 kg N as (NH4)2SO4; microplots within each plot received the same amount of15N-depleted (NH4)2SO4. Using the15N-dilution method, the percentage of N derived from N2-fixation by cowpea and the recovery of N-fertilizer and soil N-uptake was measured for both crops at 50 and 80 days after planting.Significant differences in yield and total N for cowpea and maize at both harvest periods were dependent on row spacing and cropping systems. Maize grown at the closer row spacing accumulated most of its N during the first 50 days after planting, whereas maize grown at the widest row spacing accumulated a significant portion of its N during the last 30 days before the final harvest, 80 days after planting.Overall, no significant differences in the percentage of N derived from N2-fixation for monocropped or intercropped cowpea was observed and between 30 and 50% of its N was derived from N2.At 50 DAP, fertilizer and soil N uptake was dependent on row spacing with maize grown at the narrowest row spacing having a higher fertilizer and soil N recovery than maize grown at wider spacings. At 50 and 80 DAP, intercropped maize/cowpea did not have a higher fertilizer and soil N uptake than monocropped cowpea or maize at the same row spacing. Monocropped maize and cowpea at the same row spacing took up about the same amount of fertilizer or soil N. When intercropped, maize took up twice as much soil and fertilizer N as cowpea. Apparently intercropped cowpea was not able to maintain its yield potential.Whereas significant differences in total N for maize was observed at 50 and 80 DAP, no significant differences in the atom %14N excess were observed. Therefore, in this study, the atom %14N excess of the reference crop was yield independent. Furthermore, the similarity in the atom %14N excess for intercropped and monocropped maize indicated that transfer of N from the legume to the non-legume was small or not detectable. 相似文献
10.
Stay‐green: A consequence of the balance between supply and demand for nitrogen during grain filling? 总被引:14,自引:0,他引:14
Retention of green leaf area in grain sorghum under post‐anthesis drought, known as stay‐green, is associated with greater biomass production, lodging resistance and yield. The stay‐green phenomenon can be examined at a cell, leaf, or whole plant level. At a cell level, the retention of chloroplast proteins such as LHCP2, OEC33 and Rubisco until late in senescence has been reported in sorghum containing the KS19 source of stay‐green, indicating that photosynthesis may be maintained for longer during senescence in these genotypes. At a leaf level, longevity of photosynthetic apparatus is intimately related to nitrogen (N) status. At a whole plant level, stay‐green can be viewed as a consequence of the balance between N demand by the grain and N supply during grain filling. To examine some of these concepts, nine hybrids varying in the B35 and KS19 sources of stay‐green were grown under a post‐anthesis water deficit. Genotypic variation in delayed onset and reduced rate of leaf senescence were explained by differences in specific leaf nitrogen (SLN) and N uptake during grain filling. Matching N supply from age‐related senescence and N uptake during grain filling with grain N demand found that the shortfall in N supply for grain filling was greater in the senescent than stay‐green hybrids, resulting in more accelerated leaf senescence in the former. We hypothesise that increased N uptake by stay‐green hybrids is a result of greater biomass accumulation during grain filling in response to increased sink demand (higher grain numbers) which, in turn, is the result of increased radiation use efficiency and transpiration efficiency due to higher SLN. Delayed leaf senescence resulting from higher SLN should, in turn, allow more carbon and nitrogen to be allocated to the roots of stay‐green hybrids during grain filling, thereby maintaining a greater capacity to extract N from the soil compared with senescent hybrids. 相似文献
11.
D. A. Van Sanford C. T. MacKown 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,72(2):158-163
Summary Nitrogen use efficiency (NUE), defined as grain dry weight or grain nitrogen as a function of N supply, was evaluated in 25 soft red winter wheat genotypes for two years at one location. Significant genotypic variation was observed for NUE, nitrogen harvest index, and grain yield. Genotype x environment interaction for these traits was not significant. Several variables including N uptake efficiency (total plant N as a function of N supply), grain harvest index, and N concentration at maturity were evaluated for their role in determining differences in NUE. Nitrogen uptake efficiency accounted for 54% of the genotypic variation in NUE for yield and 72% of the genotypic variation in NUE for protein. A path coefficient analysis revealed that the direct effect of uptake efficiency on NUE was high relative to indirect effects.The investigation reported in this paper (No. 85-3-122) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director 相似文献
12.
The effect of inoculation with Azospirillum brasilense on growth and nitrogen utilization by wheat plants 总被引:1,自引:0,他引:1
Azospirillium brasilense is a rhizosphere bacteria that has been reported to improve yield when inoculated on wheat plants. However, the mechanisms through which this effect is induced is still unclear. In the present work, we have studied the effects of inoculating a highly efficient A. brasilense strain on wheat plant grown in 5 kg pots with soil in a greenhouse, under three N regimes (0, 3 or 16 mM NO3
–, 50 ml/pot once or twice-a -week), and in disinfected or non-disinfected soil. At the booting stage, the inoculated roots in both soils showed a similar colonization by Azospirillum sp. that was not affected by N addition. The plants grown in the disinfected soil showed a higher biomass, N content and N concentration than those in the non-disinfected soil, and in both soils the inoculation stimulated plant growth, N accumulation, and N and NO3
– concentration in the tissues.At maturity, the inoculated plants showed a higher biomass, grain yield and N content than the uninoculated ones in both soils, and a higher grain protein concentration than the uninoculated. It is concluded that in the present experiments, A. brasilenseincreased plant growth by stimulating nitrogen uptake by the roots. 相似文献
13.
Archna Suman A. K. Shrivastava Asha Gaur Pushpa Singh J. Singh R. L. Yadav 《Plant Growth Regulation》2008,54(1):1-11
The nitrogen fixing bacterial endophytes Gluconacetobacter diazotrophicus and Herbaspirillum spp. have been proposed to benefit sugarcane (Saccaharum spp. hybrids) growth. Variable populations of these endophytes exist depending upon ontogenic and climatic variations as
well. This study investigates the effect of variable chemical nitrogen application in soil on the population of endophytic
diazotrophs, acetylene reduction ability of excised roots, plant N-nutrient use efficiency and probable interactions among
different parameters in eight commercial sugarcane varieties of subtropical India. Recovery efficiency (RE), agronomic efficiency
(AE), partial factor productivity (PFP) and physiologic efficiency (PE) indicators were used for accounting N-nutrient use
efficiency. The population of G. diazotrophicus was more at N75 compared to N0 and N150, whereas Herbaspirillum population increased from N0 to N150. ARA was positively correlated with Gluconacetobacter population in rhizosphere and root, whereas it had poor correlation with Herbaspirillum population. Positive correlation of RE and AE with ARA of roots, Gluconacetobacter and Herbaspirillum populations in roots and stems indicate their positive contribution in total nitrogen uptake by the plant per kg of N applied.
Average PFP was 808.9 at N75 compared to 408.7 at N150 indicating that N was utilized efficiently at low N input status in sugarcane. Strong positive correlations of AE75 (agronomic efficiency from 75 kg N ha−1 to 150 kg N ha−1) with N-uptake (r
2 = 0.615), cane yield (r
2 = 0.758) and PFP (r
2 = 0.758) and other parameters compared to AE (agronomic efficiency from 0 kg N ha−1 to 75 kg N ha−1 or 150 kg N ha−1) correlations with N-uptake (r
2 = 0.111), cane yield (r
2 = 0.368) and PFP (r
2 = 0.190) indicated that the AE of sugarcane was strongly directed towards producing more cane yield per unit of N fertilizer
once the sugarcane plant has established using initial dose of nitrogen and thus AE75 seems to be a more appropriate indicator for accounting N-nutrient use efficiency in sugarcane. 相似文献
14.
Manguiat I.J. Singleton P.W. Rocamora P.M. Calo M.U. Taleon E.E. 《Plant and Soil》1997,192(2):321-331
Two field experiments on green manuring were conducted under upland acidic soil (pH = 4.35) conditions with the following objectives: (1) to determine the influence of inoculation site, P fertilization, and liming on the biomass production, N content, N accumulation, and N availability of S. rostrata grown in an acidic soil, (2) to compare the effectiveness of S. rostrata, P. calcaratus and urea as N sources for upland rice as affected by liming and N source-sowing time combination, and (3) to assess the effect of liming and N source-sowing time combination on % Ndff (N derived from the fertilizer), % Ndfs (N derived from soil), % FNU (fertilizer N utilization), and FNY or fertilizer N yield (kg N ha–1) of upland rice grown in acidic soil. At 2 weeks after incorporating S. rostrata (95 days after lime application), liming significantly increased N availability by more than 2-fold suggesting that the decomposition of S. rostrata by soil microflora was stimulated by lime. Liming, phosphorus application, and inoculation site improved significantly the dry biomass production, N content and N accumulation of S. rostrata; thus, enhancing its green manuring potential. Regardless of liming, S. rostrata whether applied at 0 week or 2 weeks before sowing was superior to urea in improving grain and straw yields. P. calcaratus when applied at 2 weeks before sowing also produced higher grain yield than urea. Immediate sowing of upland rice after green manure incorporation did not affect negatively the growth and development of upland rice; hence, farmers could save at least 2 weeks in their cropping calendar. N source-sowing time combination had a highly significant influence on % Ndff, % Ndfs, % FNU, N uptake, and fertilizer N yield of upland rice. However, only N uptake was influenced significantly by liming. The rice plant obtained significantly higher % Ndfs from the soils treated with green manure than those treated with urea regardless of liming. The % FNU and % Ndff from the green manures were 11-37% and 9-25%, respectively. These values are much lower than those obtained under continuously flooded soil conditions possibly because of the differences in the organic matter decomposer populations and N loss mechanisms between sloping upland conditions and continuously flooded conditions. 相似文献
15.
Recent field studies on irrigated rice at the IRRI research farm indicate efficient use of fertilizer-N based on plant uptake of applied N, (estimated by N difference), and utilization of acquired N for increased grain yield. These findings contrast with 15N uptake in microplot studies which underestimate the actual increase in plant N from added fertiliser. Constraints other than uptake efficiency, however, may govern fertiliser-N efficiency in farmers fields. In a study of 44 farmers' fields in Central Luzon, rice yields ranged from 2.5 to 6.2 t ha-1 and N uptake from 35 to 95 kg N ha-1 in plots without fertiliser-N addition. Farmers applied from 35 to 240 kg N ha-1, but there was no relationship between the N rate used by each farmer and the effective soil N supply. Mean N uptake efficiency from fertiliser by N difference was only 36%. We conclude that improved fertiliser-N efficiency by farmers will require a more information-intensive management strategy that makes N fertiliser inputs better fitted to the seasonal pattern of crop N demand and soil N supply. 相似文献
16.
Nitrogen transfer from nodulating soybean to maize or to nonnodulating soybean in intercrops: the 15N dilution method 总被引:10,自引:0,他引:10
In 1985, 1986 and 1988, maize (Zea mays L.) was monocropped or intercropped with nodulating or nonnodulating soybean (Glycine max [L.] Merr.). In addition, nodulating soybean and nonnodulating soybean were each monocropped and grown as a mixture. In 1985 and 1986, treatments were grown at 0 and 60 kg N ha–1 and in 1988, the treatments were grown without N fertilizer, on N-depeted soil and on non-N-depleted soil. 15N enriched N was applied to soil in all the aforementioned treatments to test for N transfer from nodulating soybean to non-N2-fixing crops by the 15N dilution method.The 15N dilution method did not show the occurrence of N transfer in 1985 and 1986, but the N sparing effect was evident from the total N uptake of nonnodulating soybean, dwarf maize and tall maize, in 1986. In 1988, maize and nonnodulating soybean seed yields and seed N yields were higher on non-N-depleted soil than on N-depleted soil. On N-depleted soil, the 15N dilution method indicated N transfer from nodulating soybean to maize and to nonndulating soybean. At a population ratio of 67% nodulating soybean to 33% nonnodulating soybean, N transfer was also seen on non-N-depleted soil in 1988. 相似文献
17.
半湿润地区农田夏玉米氮肥利用率及土壤硝态氮动态变化 总被引:15,自引:0,他引:15
以土垫旱耕人为土为供试土壤,通过田间试验,研究了不同施氮量下(0、45、90、135和180 kg·hm-2)夏玉米生育期土壤剖面NO3--N的变化特征、氮素利用率及施氮量与土壤NO3--N残留的关系.结果表明:在整个生育期内,土壤NO3--N含量均以0~20 cm土层最高,且施氮量越高,NO3--N含量也越高;0~60 cm土层NO3--N含量变化显著,60~100 cm土层NO3--N含量变化不大.夏玉米整个生育期,受玉米对氮素的需求和降雨的影响, 0~100 cm土层NO3--N累积量呈波动式降低趋势;当施氮量小于135 kg·hm-2时,作物氮肥利用率随施氮量的增加而显著提高,但当施氮量超过135 kg·hm-2时呈下降趋势. 氮肥农学利用率随施氮量的增加而减小,氮肥生理利用率随施氮量的增加而递增.土壤中残留NO3--N与施氮量呈极显著正线性相关关系 (R2=0.957**,n=5);施氮处理籽粒产量显著高于不施氮处理(P<0.05);施氮量与籽粒产量呈极显著正线性相关关系(R2=0.934**,n=5).在本试验条件下,夏玉米生长季适宜施氮量为135 kg·hm-2.该施氮水平可保证效益和环境的双赢. 相似文献
18.
Maize (Zea mays L.) and ricebean (Vigna umbellata [Thumb.] Ohwi and Ohashi) were grown in intercrop and monoculture on Tropaqualf soils under rainfed conditions in Northern
Thailand yearly from 1983 to 1986. De Wit's replacement design was used to compare intercrops and monocultures with a constant
plant density equivalent to 80 000 maize or 160 000 ricebean plants ha−1. Combined nitrogen was applied at varying levels to 200 kg N ha−1. In the final two seasons the intercrop ratio of maize: ricebean was also varied. At the time of maize maturity intercrops
yielded upt 49 kg ha−1 more N in the above ground plant parts than the best monoculture. Dry matter, grain and nitrogen yield of maize and ricebean
in intercrop relative to their monoculture yields (RY, relative yield) were significantly greater than their respective share
of the plant population. Relative yield totals (RYT) for grain, dry matter and nitrogen were always greater than 1.
Nitrogen uptake per maize plant increased with progressive replacement of maize by ricebean plants. This increase was similar
to that obtained by applying combined N. Available soil nitrogen tended to decrease with increasing maize:ricebean ratio.
Increasing the maize:ricebean ratio increased the % of nitrogen derived from fixation in ricebean, the increase being equivalent
to that obtained by decreasing combined nitrogen application. Approximately the same amount of fertilizer and soil nitrogen
was taken up by maize plus ricebean in intercrop as the maize monoculture. The results suggest that the improved nitrogen
economy of the intercrop resulted from the strong competitiveness of maize in the use of mineral nitrogen and the enhancement
of nitrogen fixation in intercropped ricebean which made it less dependent on the depleted pool of soil nitrogen. 相似文献
19.
Field studies were conducted in Niger using 15N-labeled fertilizers to assess the fate and efficiency of fertilizer N in pearl millet (Pennisetum glaucum [L.] R.Br.) production. Total plant uptake of fertilizer N was low in all cases (20%–37%), and losses were severe (25%–53%).
The majority of N remaining in the soil was found in the 0- to 15-cm layer though some enrichment at lower depths was found
when the N fertilizer was calcium ammonium nitrate (CAN). In a comparison of urea placement methods (band, broadcast, or point
placement), no significant differences in 15N uptake or yield were noted though point placement did exacerbate 15N loss. The mechanism of N loss is believed to have been ammonia volatilization. Yields were similar whether urea or CAN was
used, but 15N uptake from CAN was higher. A statistical model was developed relating millet yield and N response to midseason rainfall.
In drought years, no N response was found, whereas in years of good rainfall a response was found of 15 kg grain for each
kilogram of N applied (at 30 kg N ha-1 rate). 相似文献
20.
Summary Two15N-labelled slow-release nitrogen (N) sources, oxamide and isobutylidene diurea (IBDU), each at two particle sizes, and15N-labelled urea were compared at two rates as sources of N for rice (Oryza sativa) under two watering regimes which simulated a transplant (continuous flood, CF) and a direct-seeded (A/F) system of paddy
rice culture.
Highest grain yields were obtained from −8+10-mesh oxamide particles applied at the rate of 2,000 mg of N/5 kg of soil, CF
series; this yield was slightly higher than that obtained from −3+4-mesh oxamide, A/F series. Incubating the N fertilizers
in moist (22% water) soil for 21 days immediately before flooding and transplanting rice greatly reduced N supply because
of nitrification during the preflood period, followed by denitrification after flooding. This resulted in less plant uptake
of N and less grain yield from urea, fine oxamide and IBDU, A/F series. For coarse oxamide, N release during the preflood
period resulted in higher N uptake and grain yield in the A/F rather than in the corresponding CF series.
The pattern of fertilizer N uptake by rice plants was affected by kind of fertilizer, particle size of oxamide and IBDU, and
watering regime. Uptake of fertilizer N generally paralleled uptake of soil N throughout the growth period. Plant tops continued
to accumulate some N during the period of grain filling, but much of the N in plant tops was translocated to the grain after
heading. There was a large decrease in dry weight, N content, and15N content of tops after heading. Root weight and N content increased rapidly at first, and then at a diminishing rate until
maturity.
Unexplained N deficits occurred in the CF series (14–23% of the N applied, depending on N rate and source), and in the A/F
series for IBDU (37–43% of the N applied). 相似文献