Evaluation of integrated nutrient diagnosis techniques to enhance productivity and quality in greenhouse rose crops

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1 Progress Report Evaluation of integrated nutrient diagnosis techniques to enhance productivity and quality in greenhouse rose crops Raul I. Cabrera, John J. Franco-Hermida and Miguel Guzman 2 Department of Plant Biology & Pathology Rutgers University, Agricultural Research & Extension Center 2 Northville Road, Bridgeton, NJ Tel: cabrera@aesop.rutgers.edu Collaborating PhD Student, Protected Agriculture Program, University of Almeria, Spain 2 Collaborating Professor, Protected Agriculture Program, University of Almeria, Spain Report Date: June 30, 206 (205-6 Final Report) Funded by the Joseph H. Hill Memorial Foundation, Inc. ICFG-HILL, P.O. Box 99, Haslett, MI 48840

2 2 As mentioned in our previous report, we are working on the development and validation of integrated nutrient diagnostic techniques - like Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND) for greenhouse rose crops. These nutrient diagnostic techniques offer the prediction and correction of nutritional imbalances that significantly affect crop productivity, and which often are not diagnosed by the conventional critical nutrient range (CNR) method. Briefly, DRIS and CND systems are based on the comparison of the results of plant tissue analysis with indices that quantify, in a hierarchical order, the effect of each nutrient on the crop nutritional balance. The index values will indicate whether a possible nutrient excess (positive value) or nutrient deficiency (negative value) is happening. Using a database of almost 2,000 foliar analysis and their associated flower yields from different rose cultivars grafted on R. 'Natal Briar', and through a tedious statistical process, we were able to generate DRIS and CND norms. The most significant and interesting observation of this statistical exercise was that application of the traditional critical nutrient range (CNR) method would not have distinguished any potential nutrient imbalances nor predicted the potential flower yield differences in two different rose plant populations, and which were detected by the integrative DRIS and CND methods. The nutrient diagnostic norms we generated were thereafter validated at the theoretical level, employing other (different) datasets, including some from previous studies. We proceeded to carry out an experimental validation of the generated DRIS norms, aiming at verifying an actual practical application of this integrative nutrient diagnostic method. To this end we procured an experimental block of two-year old Freedom rose plants (grafted on Natal Briar ) in a commercial rose greenhouse in Chía, Colombia. The block consisted of 6 soil beds (3 ft. wide x 00 ft. long) with a planting density of plant per sq.ft. The well-drained, amended clay-loam soil had a ph of 6.3, an EC of 2. ds/m (in saturated past extract), organic matter content of 7.%, and a CEC of 25.9 meq/00g. Fertigation was carried out with a dual line drip irrigation system. Baseline nutrient status of the soil beds and the rose plants were obtained, chemically analyzed and then diagnosed through the use of conventional CNR methodology and the recently generated DRIS norms. The CRN method indicated the foliar P and Fe concentrations were high, whereas the DRIS method only showed Fe as very high (Table ). The CRN method identified Mn and Cu leaf concentrations as low, whereas DRIS categorized Zn as low and Cu as very low. Regarding the DRIS assessment, this methodology indicates that any nutrient that has a negative index of lower value in relation to the indexes of other nutrients, and higher in absolute value than the mean nutritional balance index (NBIm), can be considered a very limiting nutrient by deficiency (Wadt, 999). Conversely, a nutrient with a positive index of higher value in relation to the indexes of other nutrients, and higher in absolute value than NBIm will be deemed a primary limiting nutrient by excess (i.e. leading to potential nutrient imbalances or disorders). According to DRIS theory, when all the nutrient indexes equal and/or approach zero (Mourão-Filho, 2004), or are at/below the NBIm (Wadt, 999), the closer a plant/crop will be to the adequate or optimum nutrient balance, and by logic it should correlate with the best yield and/or quality responses. Based on these preliminary DRIS results, we proceeded to set fertilization treatments addressing the most limiting nutrient excesses and deficiencies, namely those having indexes with absolute values above the NBIm, in this case Fe, Zn and Cu. DRIS theory indicates that these elements have the greatest potential to respond to fertilization changes (Hernandez et al., 204; Wadt, 999). We thus proceeded to reduce Fe applications and increase Zn and Cu applications, as shown in the fertilization treatments shown in Table 2.

3 3 Table. Results from the baseline (preliminary) leaf tissue analyses, and their assessment by the critical nutrient range (CNR) and the DRIS diagnosis methods. Nutrient Avg. Leaf x Concentration CNR Assessment DRIS Index DRIS Assessment N 4.02 Normal 0.9 Normal P 5 High 3.4 Normal K.87 Normal -4.3 Normal Ca.78 Normal 4. Normal Mg Normal -0.4 Normal S Normal Fe 64 High 32.9 Very High Mn 88 Low -5.2 Normal Zn 30 Normal -8.5 Low Cu 3 Low -2.6 Very Low B 60 Normal -2. Normal NBI NBIm x Units: N, P, K, Ca, Mg, S in %; Fe, Mn, Zn, Cu, B in mg/kg. y NBI= nutrient balance index (sum of all DRIS values, regardless of sign) z NBIm= mean (average) nutrient balance index (NBI divided by the # of evaluated elements). We started with a base nutrient fertigation solution (T0). The other four treatments (T to T4) had their Fe concentration reduced by 60% (from 4 to.6 ppm). Treatments T2, T3 and T4 had their Zn and Cu concentrations increased by 5% ( to.5 ppm) and 30% ( to.3 ppm), respectively, over the control fertigation solution (T0). Finally, treatment 3 (T3) was supplemented with weekly foliar applications of 30 mg/l of EDTA quelated Cu, whereas treatment 4 (T4) was supplemented with weekly foliar applications of 30 mg/l of EDTA quelated Cu and 5 mg/l of EDTA quelated Zn (Table 2). Table 2. Fertigation treatments designed after DRIS analyses and assessment on preliminary leaf tissue analysis in an experimental block of Freedom rose plants (on rootstock R. Natal Briar ). These fertilization treatments (two of which included foliar applications) were used over an -week production cycle, and flower yield, quality and nutrient status evaluated with critical nutrient range (CNR) and DRIS diagnosis methods. Nutrient concentrations in mg/l. Treatment N P K Ca Mg S Fe Mn Zn Cu B T0 (control) x T T T3 + foliar y T4 + foliar z x Standard fertigation formula y Additional weekly foliar applications of 30 mg/l of EDTA quelated Cu.

4 4 z Additional weekly foliar applications of 30 mg/l of EDTA quelated Cu and 5 mg/l EDTA quelated Zn. All the rose plants in the experimental block were pruned to synchronize their flowering and immediately exposed to the fertilization treatments (fertigation and foliar applications as per each treatment). While this experimental production cycle was conducted over an -week period, leaf tissue samples were collected on week 9, including leaves from the st and 5 th position immediately below a flower bud starting to show color (sepals starting to reflex and show the colored petals). The chlorophyll index in the collected leaves was determined with a Minolta SPAD-502 Chlorophyll Meter. The leaf samples were then dried and subjected to mineral analysis. Flowers were harvested up until week from the onset of the fertilization treatments, quantified and graded according to their length (following standard export grades). Table 3. Nutrient concentrations and DRIS index values in leaf tissue of Freedom roses (grafted on R. x Natal Briar ) after a 9-week period with fertilization treatments aimed at correcting DRIS-diagnosed nutrient excesses (Fe) and deficiencies (Zn and Cu). Details of fertilizer treatments are shown in Table 2. Treatment N P K Ca Mg S Fe Mn Zn Cu B NBI x NBIm y Foliar Concentration z T0-control a 6 8 T a 2 T ba 9 T3+foliar ba T4+foliar b a 79 a 29 b 3.9 b ba 57 b 29 b 3.9 b ba 59 b 44 a 8. a ba 62 b 45 a 3.8 a b 52 b 38 ba 3.2 a 72 DRIS Index T0-control a a 25.8 a -7.2 a c ab 6.4 ab T a a 8.8 b -4.8 ba c a 7.2 a T b a 6.0 b -6.9 b b b 5. b T3+foliar b b 5.5 b -5.5 ba a ab 6.9 ab T4+foliar b a 2.6 b -2.4 b a ab 6.8 ab x NBI= nutrient balance index (sum of all DRIS values, regardless of sign) y NBIm= mean (average) nutrient balance index (NBI divided by the # of evaluated elements). z Foliar concentrations in % for macronutrients and mg/kg for micronutrients. Values with the same letter in each column are not significantly different (Tukey =0.05). Tissue analyses indicate that after 9 weeks, the reduced Fe supplies in treatments T to T4 caused reductions in leaf Fe concentrations compared to the control treatment T0 (Table 3). The leaf tissues concentrations of Zn and Cu were significantly increased with higher fertigation concentrations and supplemental foliar applications (T2 to T4) with respect to the control and T treatments that had only baseline Zn and Cu concentrations in the fertigation formula. Interestingly, leaf P concentrations were reduced in T2, T3 and T4 treatments, highlighting the often-reported antagonisms between these elements in other crops (Fageria, 200; Marschner, 995; Murphy et al.,

5 5 98). It thus appears that enhanced zinc and copper supplies in rose crops can certainly affect the uptake and/or assimilation of phosphorous. Similar to the trend in leaf Fe concentrations, the Fe DRIS index was reduced in the T- to T4 treatments, an expected response considering they received only 40% of the Fe supply in the fertigation control (T0) treatment (Table 3). Nevertheless, Fe continued to be found as the most excessive elements, denoted by having the highest positive DRIS index values across most of the fertilization treatments. The Cu DRIS indexes were increased by the additional Cu to the soil (T2), but reached significantly higher values with the added foliar applications (T3 and T4). This observation highlights a great sensitivity of the DRIS diagnosis system to excessive foliar applications for this element. A similar response pattern, yet not as extreme, was observed for the Zn DRIS indexes, increasing their values with supplemental Zn applications to the soil solution and foliage (i.e. T2 to T4). A striking observation was that the Mn foliar concentrations and Mn DRIS index were significantly increased in all modified fertilization treatments (T to T4) compared to the control fertigation solution (Table 3). These highly responsive micronutrient interactions between Mn and Fe, Zn and Cu have also been reported in other agronomic and horticultural crops (Fageria, 200; Marschner, 995). Regarding the total and mean nutrient balance indexes (NBI and NBIm, respectively), these were found to be statistically lower only in T2 (Table 3). Overall, this fertilization treatment was thus the most successful, in this trial, towards the correction of the imbalances of Fe (excess), and Zn and Cu (deficiencies) originally diagnosed in this experimental Freedom rose crop. Nevertheless, it is clear that after 9 weeks of applying the fertilization treatments, all treatments including the control- led to significant imbalances in the status of Mn in leaf tissues, technically very limiting deficiencies as denoted by the NBIm values (Table 3). On this first experimental validation run we did not observe significant differences in flower yields, nor in flower stem lengths (Table 4). It should be noted, however, that the flower yields in treatment T2, which had the lowest NBI and NBIm indexes (i.e. better nutrient balance), were 7% higher than the average flower yields for all the other treatments including the control. The foliage chlorophyll levels increased in all the modified fertilization treatments (T to T4) with respect to the T0 control (Table 4), being significantly the highest in T4. It is interesting to observe that increases in the DRIS indexes for Zn and Cu (becoming less negative or even positive; Table 3) and significant reductions in the Fe DRIS index, a result of their adjustments in the fertilization program, coincide with the observed increases in chlorophyll levels in these T to T4 treatments with respect to the control (T0). Table 4. Flower yield, harvested stem length grading fractions and foliage chlorophyll levels in Freedom roses (grafted on R. x Natal Briar ) after a 9-week period with fertilization treatments aimed at correcting DRIS-diagnosed nutrient excesses (Fe) and deficiencies (Zn and Cu). Details of fertilizer treatments are shown in Table 2. Treatment Flower Stem Length Grading y Chlorophyll Index z Yield x % 40 s % 70 s % National Leaf Leaf 5 T0 (control) b 50.8 b T ba 5.3 b T ba 52.6 ba

6 6 T3 + foliar ba 52.4 ba T4 + foliar a 53.8 a x Harvested flower yields expressed in flowers/m 2 /year. y Fraction of harvested flowers with cm lengths (40 s), cm lengths (70 s) and non-exportable lengths (National). z SPAD Units. Values with the same letter in each column are not significantly different (Tukey =0.05). Based on our previous research experience, we know that the nutrient and carbohydrate reserves of rose plants is such that it takes months before we are able to observe significant responses to fertilization treatments. We are using the results and data from this first DRIS experimental validation run to do a second flower production cycle, where we feel we should get closer to achieving a more balanced nutrient status in the crop, and which should produce significant results in flower productivity and quality. We have also started an experimental plot with container-grown roses (Fig. ) to evaluate the usefulness of employing leaf tissue nutrient status expressed on a leaf area basis versus the conventional dry weight basis. We have run into an unexpected technical difficulty, in that the cultivar (graciously provided by a California rose grower) we have (grafted on Natal Briar ) has a tendency to significantly defoliate at the slightest environmental stress (over- and under-irrigation, fluctuating ambient light levels, insect pressure). We are hoping to have soon a new set of sizable plants (different cultivar) that will allow us to conduct this study. Figure. Overview of the container-grown experimental plot to test the usefulness of employing leaf tissue nutrient status expressed on a leaf area basis versus the conventional dry weight basis. REFERENCES Cabrera, R.I Mineral Nutrition. In: A. Roberts, S. Gudin, and T. Debener (Eds.), Encyclopedia of Rose Science, p Academic Press. London, UK. Beaufils, E.R Diagnosis and Recommendation Integrated System, DRIS. General scheme of experimentation & calibration based on principles developed from plant nutrition. Soil Sci. Bull. :- 32 Fageria, V Nutrient interactions in crops plants. J. Plant Nutr. 24(8):

7 7 Hernandes, A., H.A. de Souza, D.A. de Amorim, W. Natale, J. Lavres Jr., A. Enedi-Boaretto, M.A. Camacho DRIS norms for Pêra orange. Comm. Soil Sci. Plant Anal. 45: Jones, C.A. 98. Proposed modifications of the Diagnosis and Recommendation Integrated System for interpreting plant analyses. Comm. Soil Sci. Plant Anal. 2: Lucena, J.J Methods of diagnosis of mineral nutrition of plants: A critical review. Acta Hort. 448: Marschner, H Mineral Nutrition of Higher Plants, 2 nd Ed. Academic Press. London. Mourão-Filho, F.A.A DRIS: Concepts and applications on nutritional diagnosis in fruit crops. Sci. Agric. 6(5): Murphy, L.S., R. Ellis Jr. and D.C. Adriano. 98. Phosphorus micronutrient interaction effects on crop production. J. Plant Nutr. 3(-4):