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1.
Improving nitrogen use efficiency is important for the potato crop, because of its relatively low ability to take up available soil mineral nitrogen (N). Splitting of N fertilizer application is a suitable approach to better match N need and supply. In-season crop N monitoring methods are therefore required to support such strategies. This paper deals with the state of the art and potential development of characteristics, use and implementation of well known and more recent methods aimed to assess in-season potato Crop Nitrogen Status (CNS). A short overview of this concept is given for the potato crop. The most important and available methods for CNS assessment are evaluated for their accuracy, precision, sensitivity, sensibility and feasibility. These are: the petiole sap nitrate concentration test; the leaf chlorophyll concentration measurement using a hand-held chlorophyll meter; the measurement of crop light reflectance through a hand-held radiometer using passive sensors. More recent methods still under investigation based on near, ground-based, air-borne or space-borne remote sensing are discussed for their scientific and practical interest in the near future. The current and potential use and implementation of these methods into decision support systems for potato N fertilization management aimed at improving the potato crop nitrogen use efficiency are analysed by: comparing relative and raw data; establishing threshold values of CNS; and combining or integrating the CNS values into models dedicated to N recommendation or to crop growth simulation.  相似文献   

2.
J. Vos  M. Bom 《Potato Research》1993,36(4):301-308
Summary A field experiment with potato (Solanum tuberosum L., cv. Vebeca) was conducted on a sandy soil near Wageningen (52° North) in 1992. The treatments included a zero-nitrogen control and combinations of three amounts of nitrogen, viz. 110, 180 and 250 kg N ha−1, and splitting of the N dose in one (early May), two (early May and June) or three (early May, June, July) applications. The chlorophyll content of the uppermost fully grown leaves was assessed with a SPAD-502 chlorophyll meter (Minolta, Osaka, Japan) throughout the season. The pattern of change with time in SPAd-values differed between treatments. SPAD-502 readings correlated well with laboratory measurements of the chlorophyll content and with the nitrogen concentration in leaves (r 2>0.95). Data on the nitrate concentration in petiole sap (included as a reference) showed that this variable responded much more to split nitrogen applications than the SPAD-value. Future research will need to consider other factors which may affect the chlorophyll content of the foliage.  相似文献   

3.
The objective of this paper was to investigate the influence of different nitrogen (N) application rates to some morphological and physiological features of leaf blades, including leaf thickness, chlorophyll content at different leaf ages and chlorophyll a/b ratios. A paddy field and a cement tank experiments were conducted simultaneously. Rice leaf thickness was measured through a specially developed displacement sensor. Meanwhile, chlorophyll content was estimated using chlorophyll meter (SPAD) and spectrophotometer after ethanol extraction of leaf samples. With the increase of N application, leaf thickness became thinner and chlorophyll a/b ratios decreased. Moreover, the sensitivity of the SPAD readings of the same leaf at different leaf ages to N rates was assessed through coefficients of variation (CV). CV of SPAD readings increased from 8.8% to 21.6% during leaf lifetime, which indicates that SPAD readings became more and more sensitive to nitrogen rates as leaf aged. Therefore, SPAD readings of the lower leaves, which were physiologically older than the upper ones, were more sensitive to nitrogen rates.  相似文献   

4.
Nitrogen (N) management is critical in optimizing potato yield and quality and reducing environmental pollution. Six N rates from 34 to 270 kg ha−1, and different timing of N application were used in a 3-year field experiment to contrast SPAD-502 chlorophyll meter and QuickBird satellite imagery data against the conventional petiole sampling technique for assessing canopy N status. Overall treatment variations in SPAD readings were consistent with those in petiole nitrate-nitrogen (NO3-N) concentrations. However, the ability of the SPAD meter to detect treatment differences varied with growth stage and growing season. Severe N deficiency was detected about 1 month after emergence with SPAD readings, but as early as 2 weeks after emergence with petiole NO3-N concentrations. Petiole NO3-N concentrations tended to differentiate more treatment variations than SPAD readings at all growth stages except at hilling. N deficiency was detected with QuickBird image-derived vegetation indices (VIs) at the hilling stage in 2002, but not in 2003. At the post-hilling stage, treatment differences in VI values were minimal and insignificant except very late in the growing season. SPAD meters could be used as an indirect method for detecting N deficiency at the hilling stage when making supplemental N applications, but they are not as sensitive as the petiole sampling method. The sensitivity of QuickBird imagery to canopy N variations needs to be further tested with more pixel data. However, cloud interference and high cost of images could limit the use of QuickBird data in making timely management decisions.  相似文献   

5.
Optimum rate and timing application of nitrogen (N) fertilizer are most crucial in achieving high yield in irrigated lowland rice. In order to assess leaf N status, a semidwarf rice cultivar (Khazar) was grown with different N application treatments (0, 40, 80, and 120 kg N ha−1 splited at transplanting, midtillering, and panicle initiation stages) in a sandy soil in Guilan Province, Iran, in 2003. The chlorophyll meter (SPAD 502) readings were recorded and leaf N concentrations were measured on the uppermost fully expanded leaf in rice plants at 10-day internals from 19 days after transplanting to grain maturity. Regression analysis showed that the SPAD readings predicted only 23% of changes in the leaf N concentration based on pooled data of leaf dry weight (N dw) for all growth stages. However, adjusting the SPAD readings for specific leaf weight (SPAD/SLW) improved the estimation of N dw, up to 88%. Specific leaf weight (SLW), SPAD readings, leaf area and weight as independent variables in a multiple regression analysis predicted 96% of the N dw changes, while SPAD readings independently predicted about 80% of leaf N concentration changes on the basis of leaf area (N a). It seems that chlorophyll meter provides a simple, rapid, and nondestructive method to estimate the leaf N concentration based on leaf area, and could be reliably exploited to predict the exact N fertilizer topdressing in rice.  相似文献   

6.
马铃薯氮素营养状况的SPAD仪诊断   总被引：6，自引：2，他引：4  
以马铃薯品种克新1号为材料,研究了叶片SPAD值、叶片全氮含量、叶绿素含量以及块茎产量随供氮水平的变化规律及相互关系,旨在为使用叶绿素仪进行马铃薯无损伤氮素诊断和推荐施肥奠定基础。研究结果表明,从马铃薯苗期到块茎淀粉积累各个生育阶段叶片的SPAD测定值均与马铃薯叶片含氮量呈显著正相关关系。除苗期外,块茎形成期、块茎膨大期、淀粉积累期的马铃薯叶片含氮量和叶片SPAD值随土壤施氮量的变化均表现为线形加平台的模式。因此马铃薯块茎形成期后叶片的SPAD读数可揭示马铃薯的氮素营养状况。统计分析结果还表明,叶片SPAD值与块茎相对产量呈线形加平台的数量关系模式,据此确定了应用叶绿素仪SPAD-502进行马铃薯推荐施肥的SPAD临界值为块茎形成期47.3、块茎膨大期45.1、淀粉积累期40.2。  相似文献   

7.
Summary Seed potatoes of cvs Record and Bintje were grown with 30, 80 or 130 kg N/ha. In the subsequent growing season the seed tubers, which were inoculated or not with two concentrations ofErwinia carotovora subsp.atroseptica (Eca), were subjected to the same fertilization treatment. The incidence of blackleg and the level of seed tuber decay increased from the uninoculated treatment to the higher inoculum level, but the degree varied considerably from one year to another. Cv. Bintje was more susceptible to blackleg and yield loss caused by Eca than cv. Record. In 1990, when disease incidence was high, the proportion of blackleg stems increased with increasing doses of nitrogen fertilizer which had been applied to the seed crop, but was not significantly affected in 1988 and 1992. Seed tuber decay was retarded by the lowest nitrogen dose. The yield of the subsequent crop was not affected by the nitrogen dose applied to the seed crop.  相似文献   

8.
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   

9.
《Plant Production Science》2013,16(3):185-189
Abstract

The correlations of the reading of a portable chlorophyll meter (SPAD-502) with the chlorophyll and N contents of leaves of two faba bean (Vicia fabaL.) cultivars, Japanese (Ryousai-issun) and Egyptian (Cairo 241), were examined. The SPAD readings positively correlated (ρ<0.01) with the chlorophyll contents and the r2 values were 0.99 and 1.00 for Ryousai-issun and Cairo 241, respectively. A close linear relationship (ρ0.001) was observed between SPAD reading and total leaf N content at the pod development stage of faba bean plants with r2 = 0.88 and 0.99 for Ryousai-issun and Cairo 241, respectively. The SPAD reading was the highest in the 2nd to 4th leaves counted from the top (the youngest fully expanded leaves). The changes in leaf chlorophyll content of both cultivars from 3 weeks after transplanting to the ripening stage showed an incomplete “M” type curve. SPAD readings were significant¬ly higher in Ryousai-issun than in Cairo 241 throughout the growth season. Organic fertilizers application improved faba bean plant growth. These results suggest that the SPAD-502 chlorophyll meter can be used to measure chlorophyll and nitrogen contents of faba bean leaves for quick screening faba bean genotypes.  相似文献   

10.
《Field Crops Research》1998,56(3):309-314
A two-location experiment was carried out at five to six nitrogen levels to study the relationship between chlorophyll-meter readings (SPAD values) and physiological or yield traits in short-season cotton. The results showed that there were highly significant (P<0.01) linear relationships between SPAD values and contents of both nitrogen and chlorophyll at each growth stage, and as well as with the daily increase in plant height during early flowering. The relationship between nitrogen concentration and SPAD was stronger when nitrogen was expressed on a leaf area (Na) rather than on a dry weight (Ndw) basis. Significant curvilinear relationships were found between SPAD values at various stages and photosynthetic intensity, lint yield, and total boll number per hectare, respectively. Furthermore, the linear regressions between SPAD values and N fertilizer levels were highly significant (P< 0.01), and before the boll opening stage, the slopes of these regressions were similar (0.040–0.041) at the two locations. These data provided evidence that the chlorophyll meter could be used to determine sidedress N requirements of short-season cotton before boll opening stage. Critical SPAD levels for maximum lint yield were established as 32.4, 33.1, 35.0, 43.55, and 39.7 at early flowering, flowering peak, boll forming, the beginning of boll opening and boll opening stages, respectively. It was also established that 24.2–25.0 kg ha−1 increase in N application should be necessary for each unit decrease in SPAD value below the critical level.  相似文献   

11.
《Plant Production Science》2013,16(1):100-108
Abstract

Excessive nitrogen fertilization results in low nitrogen-use efficiency. To improve nitrogen management for high yield and high nitrogen efficiency in rice and wheat, we developed a knowledge-based nitrogen fertilization model by integrating the quantitative relationship between N fertilization and yield target with respect to N supply and demand balance. The total amount of nitrogen and ratio of basal to top dressing nitrogen could be determined by this nitrogen fertilization model, and the desirable nitrogen fertilizer strategies could be made under the conditions of different climates, soil types and managements. Furthermore, the function of dynamic regulation of pre-designed N dressing rate could be determined by using the nitrogen fertilization model on the basis of actual growth status under a specific production system. The nitrogen fertilization model is evaluated using the data from field experiments of rice and wheat at Nanjing, and the results on crop growth pattern and N use showed that the grain yield and N recovery were markedly improved by the N fertilization plan given by the model. The nitrogen fertilization model can be used as guidance for quantifying N fertilization strategy in cereal crop production.  相似文献   

12.
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   

13.
J. Vos 《Potato Research》1997,40(2):237-248
Summary The response of potato to different rates of nitrogen supply ranging from 0–40 g m−2 N was studied in five field experiments near Wageningen. NL (520 North). In total two late potato cultivars and two sites were used during successive seasons. The results are summarized in a set of regression equations separately for total crop and tubers. The relation between nitrogen taken up (g m−2) in the total crop and total dry matter production (g m−2) could be described with the exponential equation: 1942–1900 * 0.93X (r2=0.953, n=62). Nitrogen concentrations in the dry matter increased linearly with nitrogen uptake. Harvest indices for dry matter and nitrogen tended to decline with increase in N uptake. Cultivars differed only in the effect on N on tuber dry matter concentration. The relation between nitrogen uptake and nitrogen supply could be fitted with quadratic regression models. but coefficients were influenced by site and season.  相似文献   

14.
Optimizing nitrogen (N) fertilizer management in irrigated potato (Solanum tuberosum L.) on coarse-textured soils is challenging. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time provides approaches to improve fertilizer use efficiency while maintaining or improving yield. This 3-years replicated field plot study evaluated effects from a series of N fertilization strategies including 10 combinations of sources, placement and timing, as well as fertigation, on irrigated processing potato (cv. Russet Burbank) grown for a total of five site-years in the Province of Manitoba, Canada. Treatments were designed to provide early to late availability of N to the potato crop. Nitrogen was applied to 80% of Provincial N recommendation to increase the likelihood of observing improved fertilizer use efficiency and effects of treatments on yields. Measurements were tuber yield, size distribution, specific gravity, hollow-heart rate, fertilizer apparent N recovery (ANR) and agronomic nitrogen use efficiency (NUE). Results showed differences in yield, quality, ANR and NUE between fertilizer treatments were generally very small or absent. Average tuber marketable yields for fertilizer treatments were significantly greater than those for the unfertilized control (P?<?0.001). Split application of urea at planting and hilling, and urea at planting with fertigation occasionally increased tuber marketable yields on sites of coarse textured soils (P?<?0.05). Use of polymer-coated urea (ESN) or stabilized urea with inhibitors (SuperU) did not affect yield, quality or N use of potato. Site-year difference (P?<?0.001) were apparent for all measures highlighting the importance of soil and climatic conditions on agronomic and environmental effects of N management practices. The results indicate current grower practice of split urea application at planting and hilling and urea at planting following by in-season fertigation are sound. Results indicate growers could shift to the more convenient practice of ESN at planting without reducing yields. Absence of treatment effects suggests N was generally not a limiting factor for the current study, indicating that the current recommendation for potato production in Manitoba over-estimate site-specific crop N needs.  相似文献   

15.
Safflower (Carthamus tinctorius L.) is a deep-rooted crop which can tolerate water stress and can be grown in rotation with other crop species. Nitrogen is very important for the growth and yield of safflower, however, the effect of N level on chlorophyll content, assimilation rate, transpiration rate, stomatal conductance, substomatal CO2 concentration, and water use efficiency (WUE) have not been determined. A 2-year field study was conducted with the objective to determine the effect of N fertilization on yield, yield components, chlorophyll content, photosynthetic characteristics, and WUE of safflower grown under rainfed conditions. Three rates of N were used (0, 100, and 200 kg N ha−1) and two hybrids (CW9048 and CW9050). N fertilization increased seed yield by an average of 19%, the seed weight per plant by 60%, the seed weight per head by 18%, the number of heads per plant by 32%, and the number of seeds per plant by 41% compared with the control. N level also affected chlorophyll content, N concentration at anthesis, protein, and oil yield. N application increased assimilation rate by an average of 51%, stomatal conductance of water vapour by an average of 27%, and WUE by an average of 60% over the 2 years of the study when compared to the control. The present study indicates that N fertilization can affect yield, yield components, photosynthetic efficiency, and physiology of safflower under rainfed conditions.  相似文献   

16.
Dynamic crop models can be used to predict the occurrence of nitrogen deficiency during crop growth and optimize nitrogen fertilisation. However, prediction errors can be large and may lead to wrong recommendations. The objective of our work is to study the value of correcting the dynamic model Azodyn using transmittance measurements made with the N-Tester® (Yara) to predict the nitrogen status of a winter wheat crop. Our approach is to use a Bayesian method called the “interacting particle filter” to fit the model's state variables to measurements obtained over the course of the season. This approach was assessed on 44 experimental plots. Predictions of crop biomass, nitrogen uptake and nitrogen nutrition index were first performed for each plot by using the model without any correction. A second series of predictions was then performed for the same variables by correcting the model with N-Tester measurements at GS 7 on Feekes’ scale. The results showed that the second series of predictions were more accurate. Depending on the prediction dates, model corrections reduced the root mean squared error by 18.1–53.2% for nitrogen nutrition index, by 9.1–10.1% for biomass, and by 17.1–45.0% for nitrogen uptake. The predictions were improved up to 52 days after the measurement but the degree of improvement was higher when the prediction date was close to the measurement date. The results also showed that, when corrected, model predictions were very sensitive to values of N-Tester measurements. It is therefore necessary to use N-Tester measurements which are as precise as possible.  相似文献   

17.
Summary Pot and field experiments were carried out to test fertilizer treatments on the behaviour of potato tubers stores at 4°C and ≥90% relative humidity for 6 months. Weight losses (separated into water and dry matter) were enhanced after N and K fertilization and decreased by increasing P supply. Glucose and fructose contents were reduced at harvest by high N-fertilizer rates compared to no or low fertilization, but throughout storage reducing sugar accumulation was increased, sucrose reduction was decreased and ascorbic acid was increased. K fertilization affected the chemical composition of the tubers somewhat similar to that of nitrogen fertilization. High initial nitrate content of the tubers seemed to be increased and low nitrate values were decreased during storage. The tubers from pot experiments showed similar changes but of greater magnitude.  相似文献   

18.
For organic potato producers the two main challenges are disease and nutrient management. Both factors are limited by regulations that on the one hand prohibit the use of chemical fertilisers, especially nitrogen and, on the other hand, most synthetic pesticides. Late blight, caused by Phytophthora infestans is commonly thought to be the factor most limiting yield. 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 management with respect to disease and nutrient management is summarised. In a second part, the interactive effects of N-availability in the soil, climatic conditions and late blight were studied in the presence and absence of copper fungicides from 2002–2004 for the mid-early main-crop potato cv. Nicola. From the experimental work it became clear that copper fungicides in most cases do slow down epidemics adding an average of 3 days to the growth duration. However, only 30% of the variation in yield could be attributed to disease reduction. A model including disease reduction, growth duration and temperature sum from planting until 60% disease severity was reached, and soil mineral N contents at 10 days after emergence could explain 75% of the observed variation in yield. However, the model failed when N-supply was extremely high. The implications of the results on the management of organic potatoes with respect to cultivar choice, nutrient and disease management are discussed. In conclusion, several points emerge from the results: In organic farming, yields are foremost limited by nutrient availability in spring and early summer. The effects of late blight on yields may often be overestimated and cannot be deducted from results in conventional farming because of the strong interaction with nutrient status. Resistance clearly remains the most important strategy against late blight in organic potato production. However, as important or even more important than resistance is the early development and bulking behaviour and the ability of a cultivar to make use of organic nutrients efficiently. In the absence of efficient organic pesticides it is possible to reduce blight pressure to a certain extent by arranging the crop in small narrow fields perpendicular to the main wind direction neighboured either by non-hosts or completely resistant potatoes.  相似文献   

19.
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   

20.
Large field to field variability restricts efficient fertilizer N management when broad based blanket recommendations are used in maize (Zea mays L.). To achieve higher yields and to avoid nitrogen (N) deficiency risks, many farmers apply fertilizer N in excess of crop requirement in maize. Field experiments were conducted for five years (2005–2009) to establish and evaluate threshold leaf colour to guide in-season need based fertilizer N topdressings in four maize genotypes. Colour (of the first top maize leaf with fully exposed collar) as measured by comparison with different shades of green colour on a leaf colour chart (LCC) and maize grain yield was significantly correlated. The Cate–Nelson plot of chlorophyll (SPAD) meter/leaf colour chart values against relative grain yield of 0.93 for the experiments conducted during first two years indicated that LCC shade 5 during vegetative growth stages and LCC shade 5.5 at silking stage (R1) can guide crop demand driven N applications in maize. Evaluation of the established threshold leaf greenness during the next three years revealed that fertilizer N management using LCC 5 starting from six-leaf (V6) stage to before R1 stage resulted in improved agronomic and N recovery efficiency in different maize genotypes. There was no response to fertilizer N application at R1 stage. The study revealed that in maize, fertilizer N can be more efficiently managed by applying fertilizer N dose based on leaf colour as measured by LCC than blanket recommendation.  相似文献   

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