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1.
J. Vos 《Potato Research》1995,38(3):271-279
Summary The interaction between nitrogen supply and stem density on leaf attributes and branching was studied in two field experiments.
Stem densities included 8, 16, 24, 32 and 40 stems m−2. The low-N treatments received 5 or 10 g m−2 nitrogen, and the high-N treatments 20 or 25 g m−2.
The sizes of mature individual leaves on the main stem declined with increase in stem density and were larger for greater
N supply, with additive effects of nitrogen and stem density. The specific leaf area was not affected by nitrogen supply and
increased with stem density (range of values: 210 to 310 cm2 g−1). The leaf weight ratio was not affected by the treatments. At 8 and 16 stems m−2 basal branches contributed substantially to the total leaf area per stem: at 24 stems m−2 and higher densities the development of basal branches was negligible. Leaf area on apical branches was always smaller for
higher plant densities and lower rates of N supply. 相似文献
2.
Summary Different nitrogen sources (NO3
−, NH4
+, glutamic acid and their combinations) influenced the growth and morphogenic responses (node number, shoot length, and stem,
leaf and root dry weight) of three micropropagated potato cultivars (Spunta, Kennebec, Huinkul).
Addition of reduced nitrogen (NH4
+ or glutamic acid) in a nitrate medium increased shoot length and leaf number. The large increase in growth in plants fed
with NO3
−, NH4
+ could be explained by higher organic nitrogen content and enhanced dry matter partition to the shoot. This suggests that
reduced nitrogen source is required, at least as a supplement to NO3
−, to enhance N assimilation and growth. 相似文献
3.
Kurt Möller Johann Habermeyer Volker Zinkernagel Hans-Jürgen Reents 《Potato Research》2006,49(4):281-301
For organic potato producers, the two main challenges are disease and nutrient management. Both are limited by regulations
that on the one hand prohibit the use of chemical fertilizers, especially nitrogen, and on the other hand prohibit most synthetic
pesticides. Late blight caused by Phytophthora infestans is commonly thought to be the most yield-reducing factor. However, because there is no really effective fungicide available
to control late blight, there are virtually no yield loss data available for organic farming conditions. In this paper, the
state of the art of organic potato tuber growth under on-farm conditions with respect to disease and nutrient management is
summarized by field trials and on-farm surveys on commercial organic crops carried out in the years 1995–1998. Soil nitrogen
(N) levels, plant N uptake, disease development of P. infestans and potato yield were measured. Results indicated that N availability was most important in limiting yields in organic potato
crops. From on-farm data, a model including disease development, growth duration of the crops until foliage decay and different
parameters related to N status of the crop could explain 73% of the observed variation in yield. Only 25% of this variation
in yield could be attributed to the influence of late blight. Differences in N availability explained 48%. In conclusion,
several points emerged from the results. In organic farming, yields are mainly limited by nutrient availability in spring
and early summer. The effects of late blight on yields may often be overestimated and cannot be deduced from results in conventional
farming because of the strong interaction with nutrient status. Depending on N availability, tubers stop growing between mid-July
(70–90 kg N ha−1 uptake), the end of July (110–140 kg N ha−1 uptake) and mid-August (140–180 kg N ha−1 uptake) due to N limitations. The higher the N status of a potato crop, the longer the growing period needed to achieve the
attainable yield and the higher the probability that late blight stops further tuber growth and becomes the key tuber-yield-limiting
factor. In the second part of this paper, the interactive effects of soil N availability and the impact of P. infestans on yield in the presence and absence of fungicides from 1996 to 1998 for mid-early main crops are reported. An empirical
schematic model of disease impact depending on N availability was developed. 相似文献
4.
Summary Effects of three rates of fertilizer nitrogen, viz. 80, 160 and 240 kg N/ha, on tuber yield and dry-matter percentage in potato
cv. Record were compared in two experiments. Crop nitrogen uptake increased with application rate but total uptake differed
between experiments. Tuber yield was highest following application of 160 or 240 kg N/ha but differences between these two
rates were not significant. Tuber dry-matter percentage was reduced in one experiment with increasing nitrogen rate, but in
the second experiment final dry- matter percentage was highest following application of 240 kg N/ha. In all treatments, positive
linear relationships were found between dry matter percentage and mean fresh weight of tubers >30 mm, but within experiments,
the regression coefficients were generally reduced by increased crop nitrogen uptake. 相似文献
5.
B. J. Zebarth W. J. Arsenault J. B. Sanderson 《American Journal of Potato Research》2006,83(4):289-296
The effect of seedpiece spacing on the efficiency of nitrogen (N) use by the potato crop is generally unknown. The objective of this experiment was to determine the effect of seedpiece spacing on tuber yield, yield components and N use efficiency parameters of two potato cultivars. Potato cultivars Atlantic and Shepody were grown at two rates of N fertilization (0 or 100 kg N ha?1) and three seedpiece spacings (20, 30, or 40 cm) in 2000 to 2002. Wider seedpiece spacing increased mean tuber weight and the number of tubers per stem, but decreased total tuber yield. The higher tuber yield at the narrow seedpiece spacing was attributed to higher biomass production in combination with lower tuber specific gravity. Seedpiece spacing had no consistent effect on plant N accumulation, and therefore no consistent effect on N uptake efficiency (plant N accumulation /N supply from the soil plus fertilizer). However, a small increase in soil NO3-N concentration in the hill at topkill at wider seedpiece spacing suggested plant N accumulation was slightly reduced at wider seedpiece spacing, but at a level that could not be detected from a plant-based measure of N accumulation. The reduced dry matter accumulation, but similar plant N accumulation, resulted in lower N use efficiency (plant dry matter accumulation / N supply) at wider seedpiece spacing. Wider seedpiece spacing also resulted in generally lower values of N utilization efficiency (plant dry matter accumulation / plant N accumulation) for the 40-cm compared with the 20- and 30-cm seedpiece spacings. Effects of seedpiece spacing on N use efficiency parameters were generally consistent across cultivars and fertilizer N rates. Wider seedpiece spacing did reduce the efficiency of N use by the potato crop; however, the magnitude of the effect was small under the conditions of this study. 相似文献
6.
《Field Crops Research》2005,93(1):64-73
Leaf area growth and nitrogen concentration per unit leaf area, Na (g m−2 N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain Na and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84–6.0 g N pot−1) and five rates (0.5–6.0 g pot−1) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, Pmax, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (Na or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between Pmax and Na. The results confirm the ‘maize strategy’: leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the ‘potato strategy’ can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the ‘maize strategy’ for adaptation to N limitation. 相似文献
7.
Nitrogen and phosphorus leaching losses from paddy fields with different water and nitrogen managements 总被引:6,自引:2,他引:4
Shi-Zhang Peng Shi-Hong Yang Jun-Zeng Xu Yu-Feng Luo Hui-Jing Hou 《Paddy and Water Environment》2011,9(3):333-342
While many water-saving rice production techniques have been adopted in China, the environmental effects of these techniques
require further investigation. This study aims to assess nitrogen (N) and phosphorus (P) leaching losses under real conditions
in different water and N managements. Two water and three N treatments are conducted in the Taihu Lake region of China. Results
show that the total N leaching losses during the rice season under flooding irrigation (FI) are 12.4, 9.31, and 7.17 kg ha−1 for farmers’ fertilization practices (FFP), site-specific N management (SSNM), and controlled-release nitrogen fertilizer
management (CRN), respectively. Under controlled irrigation (CI), the respective losses were 7.40, 5.86, and 3.79 kg ha−1 for the same management methods. The total P leaching losses during the rice season under FI were 0.939, 0.927, and 0.353 kg ha−1 for FFP, SSNM, and CRN, respectively. Under CI, the losses were 0.424, 0.433, and 0.279 kg ha−1, respectively, for the same management methods. Ammonium and nitrate N accounted for 42.2–65.5% and 11.8–14.7% of the total
nitrogen leaching losses under different water and N management methods, respectively. Due to significant decrease of volumes
of percolation water and nitrogen and phosphorus concentrations in percolation water, N and P leaching losses were reduced
in the CI treatment compared to the FI treatment under the same N management. The reduction of N input and application of
controlled-release nitrogen fertilizer can reduce N and P leaching losses from paddy fields. 相似文献
8.
Measuring and predicting canopy nitrogen nutrition in wheat using a spectral index—The canopy chlorophyll content index (CCCI) 总被引:1,自引:0,他引:1
Varying the spatial distribution of applied nitrogen (N) fertilizer to match demand in crops has been shown to increase profits in Australia. Better matching the timing of N inputs to plant requirements has been shown to improve nitrogen use efficiency and crop yields and could reduce nitrous oxide emissions from broad acre grains. Farmers in the wheat production area of south eastern Australia are increasingly splitting N application with the second timing applied at stem elongation (Zadoks 30). Spectral indices have shown the ability to detect crop canopy N status but a robust method using a consistent calibration that functions across seasons has been lacking. One spectral index, the canopy chlorophyll content index (CCCI) designed to detect canopy N using three wavebands along the “red edge” of the spectrum was combined with the canopy nitrogen index (CNI), which was developed to normalize for crop biomass and correct for the N dilution effect of crop canopies. The CCCI–CNI index approach was applied to a 3-year study to develop a single calibration derived from a wheat crop sown in research plots near Horsham, Victoria, Australia. The index was able to predict canopy N (g m−2) from Zadoks 14–37 with an r2 of 0.97 and RMSE of 0.65 g N m−2 when dry weight biomass by area was also considered. We suggest that measures of N estimated from remote methods use N per unit area as the metric and that reference directly to canopy %N is not an appropriate method for estimating plant concentration without first accounting for the N dilution effect. This approach provides a link to crop development rather than creating a purely numerical relationship. The sole biophysical input, biomass, is challenging to quantify robustly via spectral methods. Combining remote sensing with crop modelling could provide a robust method for estimating biomass and therefore a method to estimate canopy N remotely. Future research will explore this and the use of active and passive sensor technologies for use in precision farming for targeted N management. 相似文献
9.
Jae Young Cho Jae Gwon Son Jin Kyu Choi Chang Hoon Song Byung Yeoup Chung 《Paddy and Water Environment》2008,6(2):211-219
The present study was carried out to evaluate nutrient losses that occur during the course of agricultural activity from rice
paddy fields of reclaimed tidal flat. For this study, we chose a salt-affected rice paddy field located in the Saemangeum
reclaimed tidal area, which is located on the western South Korean coasts. The plot size was 1,000 m2 (40 m × 25 m) with three replicates. The soil belonged to the Gwanghwal series, i.e., it was of the coarse silty, mixed,
mesic type of Typic Haplaquents (saline alluvial soil). The input quantities of nitrogen and phosphorus (as chemical fertilizer)
into the experimental rice paddy field were 200 kg N ha−1 and 51 kg P2O5 ha−1 per annum, and the respective input quantities of each due to precipitation were 9.3–12.9 kg N ha−1 and 0.4–0.7 kg P ha−1 per annum. In terms of irrigation water, these input quantities were 4.5–8.2 kg N ha−1 and 0.3–0.9 kg P ha−1 per annum, respectively. Losses of these nutrients due to surface runoff were 22.5–38.1 kg N ha−1 and 0.7–2.2 kg P ha−1 for the year 2003, and 26.8–29.6 kg N ha−1 and 1.6–1.9 kg P ha−1 for the year 2004, respectively. Losses of these nutrients due to subsurface infiltration during the irrigation period were
0.44–0.67 kg N ha−1 and 0.03–0.04 kg P ha−1 for the year 2003, and 0.15–0.16 kg N ha−1 and 0.05–0.06 kg P ha−1 for 2004. When losses of nitrogen and phosphorus were compared to the amount of nutrients supplied by chemical fertilizers,
it was found that 11.3–19.1% of nitrogen and 0.5–1.7% of phosphorus were lost via surface runoff, whereas subsurface losses
accounted to 0.2–0.8% for nitrogen and only 0.02–0.04% for phosphorus during the 2-year study period. 相似文献
10.
Physiological determinants of maize and sunflower grain yield as affected by nitrogen supply 总被引:1,自引:0,他引:1
Utilisation of nitrogen (N) has been closely related to increases in crop productivity. However, not all crops respond similarly and the objective of this study is to identify physiological processes that determine responses to N supply for maize and sunflower. Grain yield in maize (range: 210–1255 g m−2) was greater and more responsive to N supply than in sunflower (106–555 g m−2 in carbohydrate equivalents) over a wide range of total N uptake (3–>20 g N m−2). In maize, differences in grain yield among levels of N supply were associated more with variation in biomass than in harvest index. In sunflower, differences in grain yield (in carbohydrate equivalents) among levels of N supply were related similarly to variation in both biomass and harvest index. The decrease in biomass production with decreasing N supply was associated with decreases in both radiation interception and radiation use efficiency (RUE). Decreased interception was due to effects of N supply on reducing canopy leaf area, whereas the reduced RUE was associated with decreased SLN. Total biomass production in maize was more responsive to N supply than in sunflower. The major determinants of the differences in response of biomass accumulation to N supply found between maize and sunflower are: (i) sunflower tends to maintain SLN with increase in partitioning of N to leaves under N limitation whereas maize tends to maintain leaf area with increase in partitioning of biomass to leaves and (ii) the ability of maize to maintain N uptake following cessation of leaf production. 相似文献
11.
Radiation‐use efficiency for forage kale crops grown under different nitrogen application rates
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Crop growth is related to radiation‐use efficiency (RUE), which is influenced by the nitrogen (N) status of the crop, expressed at canopy level as specific leaf N (SLN) or at plant level as N nutrition index (NNI). To determine the mechanisms through which N affects dry‐matter (DM) production of forage kale, results from two experiments (N treatment range 0–500 kg ha?1) were analysed for fractional radiation interception (RI), accumulated radiation (Racc), RUE, N uptake, critical N concentration (Nc), NNI and SLN. The measured variables (DM, RI and SLN) and the calculated variables (NNI, Racc and RUE) increased with N supply. RUE increased from 0·74 and 0·89 g MJ?1 IPAR for the control treatments to 1·50 and 1·95 g MJ?1 IPAR under adequate N and water in both experiments. This represented an increase in RUE of 52–146% for the range of N treatments used in both experiments, whilst Racc increased by 9–17%, compared with the control treatments. Subsequently, the total DM yield of kale increased from 6·7 and 8 t DM ha?1 for the control treatments to ≥ 19 t DM ha?1 when ≥150 kg N ha?1 was applied. The DM yields for the 500 kg N ha?1 treatments were 25·5 and 27·6 t DM ha?1 for the two experiments. RUE increased linearly with SLN, at an average rate of 0·38 g DM MJ?1 IPAR per each additional 1 g N m?2 leaf until a maximum RUE of 1·90 g MJ?1 IPAR was reached in both experiments. There were no changes in RUE with SLN of > 2·6 g m?2 and NNI >1, implying luxury N uptake. RUE was the most dominant driver of forage kale DM yield increases in response to SLN and NNI. 相似文献
12.
This study aims to assess the nitrogen contamination of groundwater in paddy and upland fields. A reactive chemical transport
model PHREEQC and a variable saturated groundwater flow and transport model FEMWATER were used to evaluate the vertical transport
of nitrogen compound in various soil types of paddy and upland. The shallow groundwater quality monitoring data of 2003, 2006,
2009 in the Choushui river alluvial fan, the major agriculture production area in Taiwan, were applied to support the validity
of the numerical simulation findings. Results from PHREEQC and FEMWATER simulations showed that the organic-rich impermeable
plow sole layer underneath the muddy layer of rice paddy can effectively reduce NO3
− and N2 to NH4
+ and retard the movement of NH4
+. However, in the upland field which has no plow sole layer, the NH4
+ can move easily to the shallow aquifer and contaminate the groundwater. The spatiotemporal distribution of NO3
−–N and NH4
+–N in the Choushui river alluvial fan revealed that high nitrate–N contamination areas were located mainly in the upland field
of the proximal fan, where the granular unconfined aquifer was vulnerable to surface contaminants. Moreover, the unconfined
nature of the aquifer allows the oxidization of NH4
+ to NO3
− and accelerates the plume movement. High ammonium–N concentration areas were mostly dispersed in the distal-fan area where
upland planting and aquacultural farming were prevailed. The high NH4
+–N found in the northern Choushui river alluvial fan was attributed to the alternative planting of rice and upland crops,
and the plow sole layer was broken to maintain the quick drainage upland crop needs. 相似文献
13.
Mdziniso P Hinds MJ Bellmer DD Brown B Payton ME 《Plant foods for human nutrition (Dordrecht, Netherlands)》2006,61(1):12-20
The effects of vegetable type, vegetable dimensions, and solar drier load on dehydration rate; and texture, color, water activity, and carotene content of solar-dried carrots, sweet potatoes, and collard greens were studied. Mean dehydration rates (moisture loss,%/hr) for solar dried loads of 430 g/m2 and 715 g/m2 were 3.3 ± 0.30% and 3.8 ± 0.20% for carrots and sweet potatoes, respectively. Loads of 360 g/m2 and 465 g/m2 of collard greens had dehydration rates of 6.3 ± 0.10% moisture loss per hr. The results showed that vegetable type accounted for significant differences (p < 0.01) in dehydration rate, and beta-carotene content. Vegetable dimensions affected (p < 0.05) water activity. Solar drier load affected water activity (p < 0.01), and hue angle (p < 0.05). Beta-carotene contents (dry basis) of dehydrated carrot, sweet potato, and collard treatments were 10.9–17.4%, 7.6–9.8%, and 11.9–21.5%, respectively. Among the carrot treatments, the 5-mm thick slices packed at a load of 715 g/m2 contained the highest beta-carotene (17.4%, dry basis) and vitamin A activity (362 IU/g, dry basis), and good physical properties. For collard greens, the 2-cm and 3-cm wide strips packed at 360 g/m2 loads had the best combinations of high beta-carotene (21.5% and 17.2%, dry basis, respectively), vitamin A activity (357.2 and 293.1 IU/g, dry basis, respectively), and optimal color, texture, and water activity. Beta-carotene losses due to solar dehydration were 48.9–67.5%, 4.0–5.8%, and 1.9–19.8% (dry basis) in carrots, sweet potato and collard greens, respectively. 相似文献
14.
Fertilizer nitrogen (N) may be managed to increase crop production and profitability while reducing nitrate contamination of groundwater. A two-year field investigation was conducted to evaluate the effects of applied N on tuber yield and quality, dry matter production and N uptake of potato (Solanum tuberosum L. var. Russet Burbank) grown on irrigated sandy soils in Michigan. Nitrogen was applied as ammonium sulfate [(NH4)2SO4] at rates of 0, 56 and 112, kg N ha?1 in a single application at planting or 112 and 168 kg N ha?1 in split applications during the growing season. Total tuber yield generally increased with N applications up to 112 kg N ha?1. Only one of the three experimental sites showed an increase in marketable tuber yield when 112 kg N ha?1 was split evenly between planting and tuber initiation. Tuber specific gravity was not affected by N rate. Nitrogen rates of 112–168 kg N ha?1 maximized dry matter production and plant tissue N concentration at onset of maturity and harvest. Tuber N concentration at harvest ranged from 13–17 g kg?1 at two of the three locations. Values for the third experiment were 10–13 g N kg?1. Whole crop N uptake at onset of senescence ranged from 45 to 225 kg N ha?1 across all locations and treatments. An average of 67 percent of this N was found in tubers at harvest. Nitrogen fertilization exceeded N removal in harvested tubers by more than 50 kg N ha?1 only for the 168 kg N ha?1 treatment. These results indicate that acceptable tuber yield can be obtained with lower N rates than those currently used by most producers, with the potential for reducing net loss of N from the soil. 相似文献
15.
Toshisuke Maruyama Iwao Hashimoto Hiroshi Takimoto Denichi Nakade 《Paddy and Water Environment》2009,7(2):151-159
This research proposes an assessment for nitrogen (N) pollution loads potential from farmland, based on comparison of N in
objective crop yields with standard fertilizer usage. N in the objective yield was calculated using the “Standard Table of
Food Composition in Japan”. Three findings were made by considering yields removed from farmland. First, paddy rice and beans
have a low pollution potential, with rice paddies showing a negative pollution potential for N (around −14 kg/ha). Second,
almost all vegetable and orchard crops tested had a high pollution potential for N, although this differed from crop to crop.
Third, our outcomes align well with farmland pollution potential and non-absorbed nitrogen (NAN) as defined by Nishio, although
the latter and indices rely on a laborious and complicated method. The correlation coefficients were 0.745 (R
2 = 0.555). These outcomes show the effectiveness of our proposed assessment for potential environmental pollution loads. 相似文献
16.
Mukund D. Patil Bhabani S. Das Eran Barak Pratap B. S. Bhadoria Amir Polak 《Paddy and Water Environment》2010,8(2):189-198
Polymer-coated urea (PCU) is an important alternative to uncoated urea for improving nitrogen (N) use efficiency (NUE). Only
a few studies discuss their utility for lowland rice systems. A 2-year field study was conducted to examine if nitrogen loading
is reduced in lowland rice ecosystem by using mixture of PCU and uncoated urea without sacrificing yield. Five treatments
involving two mixtures of PCU with 50 and 70% coated urea each at 70 and 50% of recommended dose (80 kg N ha−1) and one with uncoated urea at 100% recommended dose were laid out in a completely randomized design. Selected plant growth
parameters and plant available N contents (NH4–N plus NO3–N) in soil solution and ponded water were measured over a period of 65 days after transplanting. Results showed no significant
difference for vegetative and yield parameters among different treatments suggesting that treatments receiving lower doses
of nitrogen exhibited higher NUE. Analysis of partial factor of productivity (PFP) for N suggested that the total N dose may
be reduced by 50% using mixtures of coated and uncoated urea. Similarly, statistically similar PFP values for treatments receiving
the same amount of total N for both years and for both total N dose suggested that the proportion of coated urea may also
be reduced to as low as 50% without sacrificing yield. Correlation analysis on nitrogen contents in ponded water and soil
solutions and the analysis of water productivity and PFP showed that soil water regime could also significantly influence
the nitrogen status in soil even when PCU are applied. In turn, both the water regime and N contents in soil ultimately influences
grain yield. Although the constant release of N from coated fertilizer ensures adequate N supply for plant uptake, it may
not completely avoid N deficit condition especially during heavy rainfall. Analysis of the developed production function suggested
that 55–65% polymer coating and about 100 cm total water input may be ideal for achieving maximum yield. The production function
was developed for PCU treatments using data observed in treatments receiving 70% recommended N dose. The range of water input
in these treatments was 86.5–174.0 cm. 相似文献
17.
This study was conducted to determine the effects of nitrogen (0, 120, and 240 kg N ha−1) and phosphorus (0, 90, and 180 kg P2O5 ha−1) doses on some tuber quality traits of the potato cultivar Agria under the ecological conditions of Erzurum in the years
2005 and 2006. The effects of N levels were significant only on the protein content of tubers while the P levels only significantly
affected the oil content of the crisps. No significant N × P interaction effects were found on any of the traits evaluated.
Based on these results, it could be concluded that the potato crop should be fertilized with 120 kg ha−1 N and that phosphorus fertilizers should be added when soils are P deficient in the Erzurum region. 相似文献
18.
《Field Crops Research》1995,41(2):65-77
Loss of nitrogen from the leaves and a reduction in specific leaf nitrogen (SLN, g N m−2) is associated with grain filling in sunflower (Helianthus annuus L.). To explore the relationship between crop radiation-use efficiency (RUE, g MJ−1) and SLN, crop biomass accumulation and radiation interception were measured between the bud-visible and physiological-maturity stages in crops growing under combinations of two levels of applied nitrogen (0 and 5 g N m−2) and two population densities (2.4 and 4.8 plants m−2). Both nitrogen fertilization and density had significant (P = 0.05) effects on crop biomass yield, nitrogen uptake, leaf area index and SLN, but the nitrogen effects were more pronounced for these and other crop variables. Linear regressions of accumulated biomass (OCdwt, corrected for the energy costs of oil synthesis in the grain) on accumulated intercepted short-wave radiation between bud visible and early grain filling provided appropriate and significantly (P = 0.05) different estimates of RUE for the pooled 0 g N m−2 (1.01 g OCdwt MJ−1) and 5 g N m−2 (1.18 g OCdwt MJ−1) treatments. When calculated for each inter-harvest interval, crop RUE varied in a curvilinear fashion during the season, with a broad optimum from 40 to 70 days after emergence of the crops, and with lower values earlier and later in the season. The reduction in RUE toward physiological maturity was particularly marked. A plot of RUE against SLN revealed a reduction in RUE at small SLN values, but the relationship may be confounded by ontogenetic changes in other factors. A published model (Sinclair and Horie (1989), Crop Sci., 29: 90–98) was used to explore the RUE/SLN relationship. The model was unable to reproduce the decline in RUE during the second half of the grain-filling period. It is suggested that an important cause of this failure may be the partition, in the model, of a fixed, rather than a variable, fraction of crop gross photosynthesis to respiration. 相似文献
19.
Summary Thre seed production in potato plants (Solanum tuberosum L.) may contribute to the persistence of potato cyst nematodes and of viruses, fungi and bacteria. In four experiments MCPA,
ethephon, 2,4D-amine, naphtylacetamide, metoxuron and gibberellic acid were tested for their potential to reduce berry formation.
MCPA (500 or 750 g a.i. ha−1 and ethephon (144 or 192 g a.i. ha−1) reduced or almost completely prevented berry set and their effect was strongly influenced by the crop growth stage at the
time of application. For both chemicals application at early bud stage was the most effective and, whereas MCPA showed no
adverse effects on tuber yield, size, dry matter content and fry colour, ethephon substantially reduced the percentage of
large tubers over 50 mm. 相似文献
20.
Summary Diurnal changes in net photosynthetic rate were measured in a furrow-irrigated potato crop and in a riverbed crop where the
water table was always maintained at 20–28 cm from the soil surface. In the irrigated crop, the photosynthetic rate during
mid-afternoon was about half the peak rate observed at noon. This reduction was accompanied by a near tripling of stomatal
resistance, a 45% reduction in transpiration, and a 5-fold increase in the difference between leaf and air temperatures. No
such changes were observed in the riverbed crop where the photosynthetic rate remained nearly constant at about 0.9 mg m−2 s−1 between 9 a.m. and 4 p.m. Tuber yield in the riverbed crop was about 30% higher than in the irrigated crop. 相似文献