Critical petiole nitrate concentration of two processing potato cultivars in Eastern Canada

Plant-based diagnostic methods of nitrogen (N) nutrition such as petiole nitrate (NO₃-N) concentration can be used to improve the efficiency of N utilization, and hence decrease the risks of N losses to the environment. Our first objective was to determine the effect of N fertilization and supplemental irrigation on the petiole NO₃-N concentration during tuber growth of two potato cultivars, Russet Burbank and Shepody, widely grown for processing in Eastern Canada. Our second objective was to establish the critical petiole NO₃-N concentration using the relationship between petiole NO₃-N concentration and the N nutrition index (NNI), an index based on the N concentration of shoots and tubers. This on-farm study was conducted at two sites in each of three years, 1995 to 1997. The N fertilization rates ranged from 0 to 250 kg N ha^?1 with three rates in 1995, six rates in 1996, and four rates in 1997. The NO₃-N concentration of petioles from the most recently mature leaves was measured on three sampling dates in 1995 and four sampling dates in 1996 and 1997. The petiole NO₃-N concentration generally decreased with time. At all sites and on all sampling dates, the petiole NO₃-N concentration increased with increasing N fertilization and was significantly greater for Shepody than for Russet Burbank. Irrigation had no consistent effect on petiole NO₃-N concentration. Petiole NO₃-N concentration was related to NNI (0.29<R²<0.62). Critical petiole NO₃-N concentrations required to reach a NNI of 1.0, indicating a situation where N is not limiting growth, were greater for Shepody than for Russet Burbank, and they decreased with time. Critical petiole NO₃-N concentrations (Y) expressed as a function of the number of days after planting (X) are Y = 4.80 - 0.055X for Russet Burbank and Y = 5.03 - 0.054X for Shepody.     

Response of four potato cultivars to rate and timing of nitrogen fertilizer

The release of three new potato (Solarium tuberosum L.) cultivars, Bannock Russet, Gem Russet, and Summit Russet, with unique plant growth characteristics, necessitates the development of appropriate N fertilizer recommendations. These three new cultivars, along with the standard cultivar, Russet Burbank, were treated with four N rates (0, 100, 200, and 300 kg N ha^?1) using two different application timing procedures (“early,” with two-thirds N applied preplant, and “late,” with one-third applied preplant). Measurements included total and U.S. No. 1 yields, petiole NO₃-N concentrations, and net returns derived from economic analysis using a processing-based contract. Each of the four cultivars showed a unique response to N application treatments. Bannock Russet achieved maximum yield and net returns with relatively small amounts of N fertilizer. It also showed no response to N application timing and had moderate NO₃-N sufficiency concentrations early in the season, that decreased markedly late in the season. Gem Russet N requirement for maximum yield was similar to that of Russet Burbank, but required a higher amount of N for maximum net returns. Gem Russet also showed no response to application timing and had NO₃-N sufficiency concentrations similar to or slightly higher than those of Russet Burbank. Summit Russet showed a strong trend for improved N use-efficiency when most of the N was applied early. On the other hand, analysis of net returns revealed a trend for greater profitability for Summit Russet when the majority of N was applied during tuber bulking. Petiole NO₃-N sufficiency concentrations for Summit Russet were generally higher than those for the other three cultivars. In comparison with some earlier studies with Russet Burbank, this research suggested lower optimal N rates and petiole NO₃-N sufficiency concentrations.     

Estimation of critical nutrient range of petiole nitrate for sprinkler-irrigated potatoes

The relationship of yield to concentration of NO₃ in petioles of potatoes (Solanum tuberosum L.) was studied as part of a comprehensive project on N use efficiency. The objective of this study was to estimate the critical nutrient range (CNR) of petiole NO₃ for Russet Burbank potatoes treated with N supplements during the season. Treatments totaled 224, 336, and 560 kg N ha^-1 for the season as NH₄NO₃ on this low N soil with one-third to one-half of the N applied at planting and the rest as periodical supplements during the season. Average yield of potatoes (74 Mt ha^-1) was highest with 336 kg N ha^-1. From this it was assumed that 224 N was optimum. Petiole NO₃ decreased through the season with linear regressions of petiole NO₃ versus time for each of three N rates accounting for variation in petiole NO₃. It was concluded that at the start of the season, the estimated CNR for petiole NO₃-N of potatoes was within the range from 9 to 13 g kg^-1. Numerically, CNR values decrease with time as the season progresses. It is concluded that until more precise calibrations are made available, the CNR approach with petiole NO₃ will be more helpful in cross checking the nutritional status of potatoes fertilized periodically with N supplements than in serving as a primary fertilizer guide.     

数字图像技术在马铃薯氮素营养诊断中的应用

应用数码相机获取马铃薯冠层图像色彩信息,探索出马铃薯氮营养状况的一种新方法。结果表明,在块茎形成期和块茎膨大期,数码相机获取的数字图像分析得到的冠层绿光与蓝光比值(G/B)与其它描述马铃薯氮素营养状况的指标如土壤无机氮、植株全氮含量、叶柄硝酸盐浓度、叶绿素仪读数均有良好的负相关关系。     

Improvement of nitrogen management in rice paddy fields using chlorophyll meter (SPAD)

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.     

Potato response to split nitrogen timing with varying amounts of excessive irrigation

Irrigation and nitrogen management are two of the most important factors affecting production efficiency and environmental quality in potato cropping systems. Field studies were conducted in 1990 and 1991 to determine the interactive effects of irrigation amount and N timing on potato yield, quality and nitrate leaching potential. Sprinkler irrigation was applied at approximately 1.0, 1.2 or 1.4 times estimated evapotranspiration (ET) to Russet Burbank potatoes grown on a silt loam soil. Following tuber initiation, a total of 132 kg N/ha was applied through the irrigation system to N treatment subplots using either six weekly 22 kg N/ha applications or 3 biweekly 44 kg N/ha applications. Excessive irrigation reduced root zone and petiole NO₃-N concentrations during substantial portions of the tuber bulking period. Biweekly 44 kg N/ha applications in 1991 produced higher and more consistent earlyseason root zone NO₃-N concentrations in the 1.2 and 1.4 ET plots than did the weekly 22 kg N/ha applications. Late-season tuber dry weight, total plant dry weight and plant N uptake were not affected by irrigation rate or N timing. However, excessive irrigation reduced U.S. No. 1 yield and yield of tubers >284 g in both 1990 and 1991 and reduced total yield in 1990. Biweekly N applications produced higher U.S. No. 1 yields than weekly N applications at all irrigation levels. Excessive irrigation also reduced NO₃-N remaining in the top 60 cm of soil at the end of the growing season. These results show that irrigating at optimal rates and applying split N at two week intervals on a silt loam soil can maximize Russet Burbank yield and quality while minimizing NO₃-N losses.     

Effect of Leaf Phosphorus and Potassium Concentration on Chlorophyll Meter Reading in Rice

Abstract

Chlorophyll meter (SPAD) is a convenient tool to estimate leaf nitrogen (N) concentration of rice plants. There is no information on the effects of leaf phosphorus (P) and potassium (K) concentration on SPAD readings and on the relationship between SPAD values and leaf N concentration in the literature. In 1996 dry season, cv IR72 was grown at the International Rice Research Institute (IRRI) and the Philippine Rice Research Institute (PhilRice) under various N, P and K fertilizer combinations. SPAD measurements were made on the topmost fully expanded leaves at mid-tillering and panicle initiation. The leaves were then detached, dried and analyzed for N, P and K. The SPAD values were highly correlated with leaf N concentration (r = 0.93 to 0.96). Fertilizer-K application did not affect SPAD values, leaf N concentration, or the relationship between the two. Phosphorus deficiency reduced leaf N concentration at mid-tillering, but increased leaf N concentration at panicle initiation when the same amount of N was applied. The SPAD values were 1 to 2 units greater for zero-P plants than P-treated plants at a given leaf N concentration at mid-tillering. At panicle initiation, the relationship between SPAD values and leaf N concentration was not significantly affected by leaf P status. These results suggest that a different regression equation between SPAD values and leaf N concentration should be used to estimate leaf N concentration of P-deficient and P-sufficient rice leaves at vegetative stage using a SPAD.     

Evaluation of the SPAD Value in Faba Bean (Vicia fabaL.) Leaves in Relation to Different Fertilizer Applications

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 2^nd to 4^th 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.     

Correlation of Chlorophyll Meter Readings with Gas exchange and Chlorophyll Fluorescence in Flag Leaves of Rice (Oryza sativa L.) Plants

Abstract

The objective of this study was to establish the correlation of the chlorophyll meter (SPAD) readings with the contents of chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the gross photosynthetic rate (P_g), and the maximum quantum yield of photosystem II (PSII) (F_v/F_m) in flag leaves of rice (Oryza sativa L.) in ripening stage. The SPAD readings significantly correlated with the Chl content, the Rubisco content, P_g and F_v/F_m (R² = 0.848, 0.648, 0.671 and 0.712, respectively), which suggests that the SPAD meter has the potential to estimate the photosynthetic capacity of the flag leaves. However, both P_g and F_v/F_m had a stronger relationship with the Rubisco content than the SPAD readings, indicating that the PSII photochemical and CO₂ assimilation capacities are strongly influenced by the Rubisco content. Therefore, accurate calibration would be indispensable to obtain the physiological information from the SPAD readings of flag leaves.     

Plant nutrient uptake and potato yield response to banded and broadcast nitrogen

The response of potato plants to banding and broadcasting of N was evaluated under sprinkler irrigation utilizing well water containing 20 to 24 ppm NO₃-N. A potato crop was grown for three consecutive years on a Wasco sandy loam soil at rates of 67, 134, 202, and 269 kg N/ha, as (NH₄)₂SO₄. At each rate of N, 58 kg P/ha as superphosphate, and 112 kg K/ha as K₂SO₄, were included. Differences in PO₄-P or K concentrations in petiole tissue were minimal with no consistant differences in NO₃-N concentration whether N was banded or broadcast. With each increment of N the NO₃-N concentration increased. Total or U.S. No. 1 yields of potatoes were not consistently different whether N was banded or broadcast. Total yields increased when N was increased from 67 to 202 kg/ha. Neither yield of U.S. No. 1 grade or dry matter content of potatoes was improved when N was increased above 134 kg/ha.     

Chlorophyll meter to predict nitrogen sidedress requirements for short-season cotton (Gossypium hirsutum L.)

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 (N_a) rather than on a dry weight (N_dw) 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.     

Yield,market quality and petiole nitrate concentration of non-irrigated Russet Burbank and Shepody potatoes in response to sidedressed nitrogen

Russet Burbank and Shepody potatoes were grown with the following four nitrogen treatments: 1) 90 kg ha^?1 at planting; 2) 180 kg ha^?1 at planting; 3) 90 kg ha^?1 at planting followed by an additional 90 kg ha^?1 side-dressed after tuber initiation; or 4) 90 kg ha^?1 at planting followed by an additional 45 kg ha^?1 sidedressing. When compared to the 90 kg ha^?1 at-planting treatment, petiole NO₃-N concentrations increased rapidly after sidedressing and were relatively constant through mid-season. Sidedressed N significantly increased total yields relative to the 90 kg N ha^?1 at-planting treatment by an average of 5.0 t ha^?1 in three of nine experiments. Three of the experiments, where yields did not significantly increase, were on sites which were not expected to respond to supplemental N based on petiole NO₃-N testing. A red clover green manure crop was the previous crop for two of these experimental sites. Petiole NO₃-N testing criteria were only partially effective in detecting sites where response to sidedressed N occurred. When compared to a single application of 180 kg N ha^?1 at planting, split application of 90 kg N ha^?1 at planting followed by a 90 kg N ha^?1 sidedressing significantly reduced total yields in one of nine experiments and did not affect yields in the remaining eight experiments. Tuber uniformity was improved in three of nine experiments by the split-N treatment. Specific gravity was not significantly affected. Use of 45 kg N ha^?1 at side-dressing resulted in similar yield as the 90 kg N ha^?1 sidedressing, although yield of large-sized tubers was often decreased with the lower N rate. Use of reduced at-planting N rates followed by sidedressed N does not appear to increase yields of non-irrigated Russet Burbank and Shepody potatoes when compared to the at-planting N rates that are currently recommended. This management approach can maintain yields at levels comparable to at-planting N programs and does provide an opportunity to reduce N application rates on sites where soil N reserves and soil amendments may make a substantial N contribution to the potato crop. Side-dressed N application can frequently improve yields and tuber size when potatoes have been underfertilized at planting; however, some inconsistency in response can be expected in regions that rely on unpredictable natural rainfall.     

增施有机肥对夏玉米物质生产及土壤特性的影响

2015和2016年在大田试验条件下,研究不施肥(CK)、常规施肥(NPK)、常规施肥+有机肥(增施鸡粪1 500 kg/hm~2,NPKM)对夏玉米物质生产及土壤特性的影响。结果表明,与CK相比,NPK和NPKM处理2015和2016年玉米产量分别增加13.62%和18.61%、36.75%和44.93%。植株叶片SPAD值、植株根系和地上部生物量均表现为NPKMNPKCK。与CK相比,增施有机肥后,土壤呼吸、硝态氮、铵态氮含量、脲酶、蔗糖酶活性均显著增高,过氧化氢酶活性降低。相关分析表明,连续两年玉米子粒产量均与拔节期、吐丝期、成熟期的SPAD值和硝态氮含量呈显著正相关,与吐丝期和成熟期的根系生物量、地上部生物量、蔗糖酶活性呈显著正相关。     

Potato Stolon and Tuber Growth Influenced by Nitrogen Form

Abstract

Potato tuber initiation and its growth are key processes determining tuber yield, which are closely related to stolon growth, and are influenced by many factors including N nutrition. We investigated the influences of different forms of nitrogen (N) on stolon and tuber growth in sand culture with a nitrification inhibitor during 2010 – 2011, and using two potato cultivars. Plants supplied with NO₃-N (N as nitrate, NO₃^-) produced more and thicker stolons than those supplied with NH₄-N (N as ammonium, NH₄⁺) at tuber initiation stage. In the plants fed NO₃-N, the stolon tips swelled or formed tubers earlier and produced more tubers than in those fed with NH₄-N. However, no significant difference was observed among N forms in terms of tuber yield at harvest, this may have been because of the shoot growth rate at tuber initiation stage was lower in the plants fed NO₃-N. During the tuber bulking stage, the difference in shoot DWs among N forms began to decrease, and the shoot DW of plants fed NO₃-N was even heavier than those fed NH₄-N in some cases. The influence of N form on potato plant growth may therefore vary with the potato growth stage.     

Responses of rice leaf thickness,SPAD readings and chlorophyll a/b ratios to different nitrogen supply rates in paddy field

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.     

Fertilizer effects on yield,mineral and amino acid composition,dietary fibre content and nutritive value of leeks

In pot experiments with greatly differing rates of N, P, S, K and Ca, dry matter (DM) yields of leek stems varied from 25 to 164 g/pot. Total-N and NO₃-N concentrations varied from 1.18 to 3.56% and from 10 to 1515 ppm in DM, respectively. Both N applications and P and K deficiency greatly increased total-N and NO₃-N content. S applications increased total-S content from 0.047 to 0.359% in DM, of which between approximately 100 to 25% were found in methionine+cystine. Total-N/total-S ratios decreased from 57 to 6 with the highest S level. P and K applications increased their respective content in DM two- and threefold. Severe Ca deficiency reduced Ca content from 0.495 to 0.045%. Iron, zinc, manganese and copper contents varied from 33–69, 14–26, 11–34 and 3.1–5.7 ppm in DM, respectively. Increasing N contents, whether due to N applications or P or K deficiency, decreased the content of all essential and some other amino acids in crude protein. Both S and severe P deficiency had a pronounced negative effect on amino acid composition and chemical score. Only glutamic acid (glutamine) and arginine were increased by increasing N contents. However, expressed as g/kg DM the concentrations of all amino acids were positively correlated with protein content. S and P deficiency reduced total dietary fibre (TDF) content of DM from 28.3 to 18.6% and 17.4%, respectively, of which between 53 and 60% were insoluble dietary fibre (IDF). Digestible energy (DE) was positively correlated with protein content (r=0.90**). In N-balance trials with rats, increasing protein concentrations (50% of total protein given as casein and supplemented with 1% methionine) raised the true digestibility (TD) of the protein from 44 to 72%. The biological value (BV) of protein was generally high, with a mean of 91.7 N deficiency tended to increase and S deficiency tended to decrease the BV.     

秸秆还田配施氮肥对麦田氮素平衡和籽粒产量的影响

为明确秸秆还田配施不同水平氮肥下麦田的氮素平衡状况,在夏玉米秸秆全部还田的基础上设置了不同的氮肥处理,测定了小麦植株全N含量、土壤硝态氮含量、氮肥氨挥发量和籽粒产量,分析了麦田不同土层硝态氮含量和积累量的变化趋势以及施氮量对氮素利用效率和麦田氮素平衡的影响。结果表明,小麦植株氮含量、植株氮素总积累量、籽粒产量均随施氮量的增加而显著增加;施加氮肥使氮素养分利用率、氮肥偏生产力显著降低。与播种时期土壤硝态氮含量相比,成熟期硝态氮含量降低,且施氮处理下土壤硝态氮含量、硝态氮积累量高于不施氮处理;硝态氮积累量主要分布在麦田土壤表层,与施氮量成正相关关系。施氮量为0、160、220、280kg·hm~(-2)时,硝态氮淋失量分别为5.04、13.10、17.10、37.26kg·hm~(-2)。氮肥的氨挥发速率在施肥后第一天达到最高,随后逐渐降低,遇到降雨或灌溉迅速降低至不施氮处理的氨挥发水平,氮肥氨挥发量与施氮量及时间存在正相关关系。160、220、280kg·hm~(-2)施氮量处理下,氮肥氨挥发量分别为0.65、0.77、1.01kg·hm~(-2)。从麦田氮素平衡来看,不施氮肥处理耗竭土壤氮素资源;施氮量为160kg·hm~(-2)时,有消耗土壤氮的风险;施氮量为220kg·hm~(-2)时,氮素投入与氮素输出保持平衡;施氮量为280kg·hm~(-2)时,有大量氮素损失到环境中的风险。为有效控制氮素淋溶和氨挥发损失,兼顾产量和节约生产成本,该区推荐施氮量为220kg·hm~(-2)。     

Nitrogen fertilization and irrigation affects tuber characteristics of two potato cultivars

Nitrogen fertilization, irrigation, and cultivars affect tuber characteristics such as tuber size, specific gravity, and N concentration. Few studies, however, have investigated the interaction of irrigation and N fertilization on the tuber characteristics of potato cultivars, particularly in Atlantic Canada. The objective of this on-farm study, conducted at four sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and six rates of N fertilization (0-250 kg N ha^-1) on the number of tubers per plant, the average fresh tuber weight, tuber N concentration, nitrate (NO₃-N) concentration, and specific gravity of the cultivars Shepody and Russet Burbank. Nitrogen fertilization increased the average fresh tuber weight, tuber N and N0₃-N concentrations, and decreased specific gravity. Effects of increasing N fertilization on tuber characteristics were often more pronounced for Shepody than for Russet Burbank, and for irrigated than for non-irrigated conditions. Shepody had greater average fresh tuber weight and tuber N concentration, lower specific gravity, and fewer tubers per plant than Russet Burbank. Supplemental irrigation increased the average fresh tuber weight and the number of tubers per plant, but it had a limited effect on specific gravity and tuber N and NO₃-N concentrations. Tuber NO₃-N con centration and specific gravity were strongly related to tuber N concentration, which in turn depended primarily on N fertilization. Incidents of lowest specific gravity and highest NO₃-N concentration occurred with a relative yield close to or equal to 1.0. We conclude that the risks of low specific gravity and high tuber NO₃-N concentration are greater when fertilization exceeds the N requirements to reach maximum tuber yield.     

Effects of moisture stress and nitrogen fertilization on tuber nitrate-nitrogen content

Moisture stress in potato plants results in a significant increase in tuber NO_3?N levels. Research plots with three irrigation treatments and four nitrogen fertilizer rates (0, 100, 200, and 500 lb N/A) (0, 112, 224, and 560 kg N/ha) were established to test the influence of soil moisture and nitrogen rate on tuber NO_3?N content. Data from these plots showed that regardless of nitrogen rate, potato tubers from plants subjected to moisture stress had NO_3?N levels approximately twice as high as tubers from plants under optimum or excessive irrigation. With low nitrogen fertilizer rates, tuber NO_3?N levels were 78 to 80 ppm under optimum and excessive irrigation treatments as compared to 144 ppm under the deficient irrigation treatment. With excessive nitrogen fertilizer rates, tuber NO_3?N levels were 151 to 154 ppm under optimum and excessive irrigation treatments compared to 370 ppm under deficient irrigation. Correlation between tuber NO_3?N and petiole NO_3?N levels suggest that moisture stressed plants have a different relationship between tuber and petiole than plants under proper to high soil moisture conditions.     

氮素供应对春玉米产量及冠层部分指标的影响与相关分析

采用辽宁地区5个地方品种进行低、中、高3个氮素水平的比较试验(N0:不施氮、N1:112 kg/hm~2、N2:225 kg/hm~2),探究氮素对玉米冠层指标的影响及与产量因素的相关性。相关、逐步回归分析表明,随着施氮量升高,品种产量和穗粒数显著提高。不同氮素水平下,冠层指标与产量因素相关性有差异。穗粒数在N0处理下,与吐丝期叶氮比(SLN)和叶片氮浓度呈负相关,相关强度排序为吐丝期SLN吐丝期叶片氮浓度;N1处理下,与乳熟期LAI呈正相关,与吐丝期叶片氮浓度和吐丝期绿叶数呈负相关,相关强度排序为吐丝期叶片氮浓度乳熟期LAI吐丝期绿叶数;N2处理下,穗粒数与冠层指标相关性不显著。百粒重在N0处理下,与吐丝期穗位叶SPAD值呈正相关,与吐丝期LAI和乳熟期穗位叶SPAD值呈负相关,相关强度排序为吐丝期LAI吐丝期SPAD乳熟期SPAD;N1处理下,与乳熟期穗位叶SPAD值呈正相关,与乳熟期LAI呈负相关,相关强度排序为乳熟期LAI乳熟期SPAD值;在N2处理下,与吐丝期比叶面积(SLA)、SLN、乳熟期绿叶数呈负相关,相关强度排序为吐丝期SLN、SLA乳熟期绿叶数。