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«International 17 Workshop th Nitrogen The was jointly organised by Teagasc and AFBI Printed by Print Depot Suggested citation Authors, 2012. Title ...»

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References Ministry of Agriculture, Fisheries and Food 2000. Fertiliser recommendations for agricultural and horticultural crops (RB209), 7th edition, HMSO, London Department for Environment, Food and Rural Affairs 2010. Fertiliser Manual (RB209), 8th edition, The Stationary Office, UK Nitrogen Workshop 2012 Plant analytical tool for nitrogen N detection status in potato crop Filipović, A.a, Poljak, M.b a Faculty of Agiculture and Food Technology, University of Mostar, Bosnia nad Herzegovina b Faculty of Agriculture, University of Zagreb, Croatia

1. Background & Objectives Nitrogen is a vital nutrient that helps plants and crops to grow, but high concentrations are harmful to people and nature. Generally, farming remains responsible for over 50% of the total nitrogen discharge into surface waters. The 1991 Nitrates Directive is one of the earliest pieces of EU legislation aimed at controlling pollution and improving water quality. Determining potato N needs and predicting the fertilization rate for the duration of the growing season cannot be based only on soil tests. Many researchers have found SPAD (potato - Westcott et al., 1991, corn - Wood et al.,

1992) and Cardy-ion meter readings (vegetable crops - Hochmuth, 1994) as reliable indicators of plant N status during the growing season. The objective of this paper is to estimate effectiveness of proposed tools in determining plant N status of the autochthonous potato variety Poluranka.

2. Materials & Methods The indigenous potato variety Poluranka was planted in the mountainous area of Šćitar (Bosnia and Herzegovina) in 2009 at 1404 m.a.s.l. Half of the total annual fertilizer nitrogen was applied at preplanting and other half before hilling, while standard doses of P2O5 (140 kg ha-1) and K2O (210 kg ha-1) were applied at pre-planting according to the soil test. For basic fertilization NPK 7:20:30 were used while additional N was applied as urea and calcium ammonium nitrate. Five N rates were applied i.e. 0, 50, 100, 150 and 200 kg N ha-1 in a randomized block design in three replicates.

Measurement by Chlorophyll meter and Cardy-ion meter were preformed on the uppermost, fully expanded mature leaf, which generally on the fourth or fifth node of stems below the top of the canopy. Measurements were made 65, 75, 85 and 95 DAS (days after sowing) on five plants per treatment. Total nitrogen concentrations in potato leaves were analyzed by the Kjeldahl method (AOAC, 1970). For statistical processing the dates GenStat 7 software (Laws Agricultural Trust, Rothamsted Experimental Station) were used.

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Nitrate-N declined with time. Cardy-ion meter readings were sensitive to plant N status resulting not only from differences in soil N availability but also environmental conditions, and possibly other factors.

Figure 1. Distribution of NO3-N values (mg kg-1) measured on four sampling occasions under increasing fertilization rate.

Bars show differences between treatment with LSD0,06=478 Figure 2. Distribution of Chlorophyll values measured on four sampling occasions under increasing fertilization rate.

Bars show differences between treatment with LSD0,06=2,89 Chlorophyll values increased slightly with higher fertilizer applications without significant differences and date of sampling has not provided linear collapse of values as vegetation ends.

Chlorophyll meter was less sensitive to fertilization or date of sampling and values were probably reflection some other environmental factors what requires further investigation.

4. Conclusion This work indicates that Cardy-ion meter readings show more sensitivity to N fertilization rate and follows values of N measured in leaves by laboratory method while chlorophyll readings were affected by some environmental conditions other than fertilization. Cardy ion meter is more reliable in detecting differences in nutrient tissue status for Poluranka potato cultivar then chlorophyll meter.

References Wescott, M.P. Stewart, V.R and Lund, R.E. 1991. Critical petiole nitrate levels in potato. Agronomy Journal 83, 844Hochmuth, G.J. 1994. Efficiency ranges for nitrate-nitrogen and potassium for vegetable petiole sap quick tests.

HortTechnol 4, 218-222.

Wood, C. W., Reeves, D.W., Duffield, R.R and Edmisten, K.L. 1992. Field chlorophyll measurements for evaluation of corn nitrogen status. Journal of Plant Nutrition 15(4), 487-500.

Nitrogen Workshop 2012

Potential indicators based on leaf flavonoids content for the evaluation of potato crop nitrogen status Ben Abdallah, F.a, Goffart, J.P.b a Gembloux Agro-Bio Tech (GxABT), University of Liège, Gembloux, Belgium b The Walloon Agricultural Research Centre (CRA-W) Gembloux, Belgium

1. Background & Objectives Nitrogen (N) fertilization strategies for potato crops aim to limit environmental pollution by improving N use efficiency. Such strategies may use indicators for the assessment of crop N status (CNS). Leaf polyphenolic (flavonoid) content appears to be a valuable indicator of CNS (Cartelat et al., 2005; Tremblay et al., 2007). Because of their absorption features in the UV part of the spectrum polyphenolic compounds can be measured by rapid and non-destructive optical methods generating chlorophyll fluorescence (Cerovic et al., 2005). The objective of this research was to compare the use of leaf flavonoid content as a potential indicator for the evaluation of CNS with other recognized plant-based indicators such as chlorophyll content measured by transmittance or reflectance.

2. Materials & Methods Trials were conducted in Belgium in 2010 and 2011 on two potato cultivars: Charlotte and Bintje.

The experiments included five N rates for each cultivar in a completely randomized block design.

Leaf flavonoid content was determined using two devices, the Dualex and Multiplex (Force-A, Paris, France). Leaf chlorophyll content was measured with a SPAD/HNT chlorophyll-meter (Yara, Oslo, Norway) and a Cropscan radiometer (Cropscan, Rochester, USA). The measurements were made periodically during potato growth from mid of June to the end of July. Results for 2010 are presented in this study (data for 2011 are still under investigation). The characteristics of the Nindicators studied here are presented in Table 1.

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After measurements were completed in the field, plant tissue samples were collected for biomass N concentration and crop yield. Nitrogen content analyses allow the calculation of N Nutrition Index, a reference method for diagnosing CNS. Data were subjected to ANOVA and orthogonal contrast analyses of linear, quadratic, and residual effects for quantitative N treatments (SAS software).

Indicator performance was evaluated on the basis of three criteria: specificity to N, stability of the measurements and earliness of the diagnosis. Accuracy and precision of the measurement were also investigated (data not shown).

Nitrogen Workshop 2012

3. Results & Discussion The significant N effect and the absence of interaction between date of measurement and N rate, enable the selection of one indicator for each cultivar among 36 studied. The results summarized in Table 2 provide the application of the three criteria.

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Specificity and stability were assessed by consistency of response to N levels across all sampling dates and by the absence of interaction with the date of measurements. The response of the measured indicators was also studied for the first date of sampling (5 and 17 DAE, respectively, for Charlotte and Bintje) in order to assess early relevant CNS. SPAD/FLV (Bintje) and NBI (Charlotte) ratios were the indicators that combined best the three criteria.

4. Conclusions Neither flavonoid nor chlorophyll content of the leaf, considered alone, was able to meet successfully all requirements. Results from use of the ratio of content of leaf flavonoid to leaf chlorophyll as SPAD/FLV or NBI suggest that these indicators could be used as valuable tools to assess potato CNS. This preliminary finding agrees with results of Tremblay et al. (2007), Cartelat et al. (2005) and Cerovic et al. (2005) and shows that these ratios improve the discrimination between N treatments. This effect is related to the inverse dependence of chlorophyll and flavonoids on CNS.

References Cartelat A., Cerovic, Z. G., Goulas, Y., Meyer, S., Lelarge, C., Prioul, J. L., Barbottin, A., Jeuffroy, M. H., Gata, P., Agati, G. and Moya, I. 2005. Optically assessed contents of leaf polyphenolics and chlorophyll as indicators of nitrogen deficiency in wheat (Triticum aestivum L.), Field Crops Research 91, 35–49.

Cerovic, Z.G., Cartelat, A., Goulas, Y. and Meyer, S.2005. In-field assessment of wheat-leaf polyphenolics using the new optical leaf-clip Dualex, In: Stafford J.V. (ed.), Precision agriculture '05, Wageningen pp.243 Tremblay, N., Wang, Z. and Belec, C.2007. Evaluation of the Dualex for the assessment of corn nitrogen status, Journal of Plant Nutrition 30, 1355-1369.

Nitrogen Workshop 2012

Quantitative evaluation of hot water extractable organic matter of organic farm soils in Japan by measurement of chemical oxygen demand with inexpensive chemicals and equipment Kanazawa, K., Takahashi, S., Komada, M., Kato, N.

National Agriculture and Food Research Organization, National Agricultural Research Center, Tsukuba 305-8666, Japan

1. Background & Objectives In response to the recent price increase of fertilizers, soil testing is being further promoted throughout Japan. As for nitrogen fertility, however, the national recommendation for available nitrogen is defined as the mineralized nitrogen during 4-week incubation (4WN), and is a less used index in soil fertility management, although it should better be considered especially in organic farming. Uezono and Kato (2012) have recently demonstrated that a far quicker and simpler method predicts 4WN fairly well. This method is a combination of hot water extraction of organic matter from soil and chemical oxygen demand (COD) measurement of the extracts, and it can be carried out without any special chemicals or equipment for laboratory use. Although it is quite promising method, for farmers to perform easily, measured values tend to be “semi-“quantitative because it is based on colour comparison with printed colour standards. The objective of this paper is to establish a quantitative still inexpensive method for COD measurement in the hot water extracts.

2. Materials & Methods Soil samples were collected from 34 fields of 15 farms, used for mostly organic vegetable production, in Ishioka City, Japan. Air-dried soil samples were analysed for 4WN, total organic carbon (TOC) and COD in the hot water extracts (80℃16h at soil/water ratio of 3 g/50 mL, (Uezono and Kato, 2012)). In the COD measurements, a commercially available set of chemical reagents (LR-COD-B, Kyoritsu Chemical-Check Lab., Corporation. 161JPY/test) and a LED type simple colorimeter (Checker HC series colorimeter/phosphate/HI 713, HANNA Instruments ・ Japan Corporation. 8,190JPY/set) were used instead of the COD measuring kit, reported by Uezono and Kato (2012). New COD measurement procedure is summarized in Figure 4.

3. Results & Discussion (1) Using glucose solution as COD standards, the combined use of the set of chemical reagents and LED colorimeter was tested for measurement range, and was turned to be useful up to 10 mgO/L (theoretical oxygen demand basis, Figure 1). Working with the COD measuring kit, reported by Uezono and Kato (2012), evaluation would be carried out in 12 levels at most, because it depends on visual observation with log-scaled printed colour standards. Using this LED colorimeter, as shown in Figure 1, measured values would be valid between 2.50 to 0.80, which enables some 170 levels evaluation, because this equipment displays at resolution of 0.01. (2) Using hot water extracts from organic vegetable field samples, relationship between TOC and COD was examined, and a considerable correlation was observed (Figure 2). (3) Using hot water extracts from organic vegetable field samples, relationship between 4WN and COD was examined, and it was found that COD values predicted 4WN fairly well (Figure 3). TOC values also predicted 4WN, and there was no significant difference in correlation to 4WN between these two measurements. (4) New COD measurement procedure is summarized in figure 4. Proposed dilution ratio of 50 theoretically enables measurement up to 25mg N/100 g dry soil, which covers quite a wide range of fertility status.

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Figure 4. Proposed procedure for the estimation of available N using chemical reagent set and simple colorimeter.

4. Conclusion This work presents a new method of the high resolution COD measurement, which promotes wider use of the recently developed simple assessment technique for nitrogen fertility by measuring hot water extractable organic matter in upland fields.

References Uezono I. and Kato N. 2012. Rapid Evaluation of Available Nitrogen in Upland Soil by Hot Water Extraction and Measurement of Chemical Oxygen Demand. Bulletin of the Kagoshima Prefectural Institute for Agricultural Development, Agricultural Research 6, 49-58 (in Japanese with English summary)

Nitrogen Workshop 2012

Satellite data potential for assessing potato crop nitrogen status at a specific field scale Goffart, J.P.a, Van Den Wyngaert, L.a, Buffet, D.b, Léonard, A.c, Defourny, P. c a Walloon Agricultural Research Centre (CRA-W), Productions and Sectors Dpt, 5030 Gembloux, Belgium b Walloon Agricultural Research Centre (CRA-W), Agriculture and Natural Environment Dpt, 5030 Gembloux, Belgium c Earth and Life Institute – Environmental Sciences, Université Catholique de Louvain (UCL), 1348 Louvain-la-Neuve, Belgium

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