Impaginato 137 Adv. Hort. Sci., 2018 32(1): 137-142 DOI: 10.13128/ahs-21148 Residual effects of bioslurry and amino acids plant biostimulant on carnation (Dianthus caryophyllus L.) flower quality A.N. Niyokuri 1, 2 (*), S. Nyalala 2, M. Mwangi 2 1 Department of Crop Sciences, College of Agriculture, Animal Sciences and Veterinary Medicine (CAVM), University of Rwanda, P.O. Box 210 Musanze, Rwanda. 2 Department of Crops, Horticulture and Soils, Faculty of Agriculture, Egerton University, P.O. Box 536-20115, Egerton, Kenya. Key words: bioslurry, carnation, flower quality, plant biostimulant, residual effect. Abstract: A greenhouse experiment was conducted in Finlays, Lemotit Flower Farm in Kenya to determine the residual effect of bioslurry and an amino acids plant biostimulant on carnation flower quality. A second flush of carnation plants growing in previous experimental plots was used. This experiment was laid out in a split plot design with three replications. Four levels of bioslurry: 0, 0.125, 0.25 and 0.5 L m-2 were applied in the main plots while four levels of plant biostimulant: 0, 2.0, 2.5 and 3.0 L ha-1 were used in the sub-plots. Results showed that there was no significant residual effect of bioslurry on studied parameters. Residual effects of plant biostimulant applied at 2.0, 2.5 and 3.0 L ha-1 resulted in a significant increase in carnation flower stalk length by 1.08 to 1.72 cm compared to control. However, there was negligible reduction of the flower stalk diameter (0.1 mm) and no significant residual effect of plant bios- timulant on flower head size. Moreover, there were no residual interactive effects of bioslurry and plant biostimulant on studied parameters. These results suggest that plant biostimulant can be used to improve the flower stem length in the subsequent flush of carnation plants supplied with a full dose of inorgan- ic fertilizers. 1. Introduction Carnation (Dianthus caryophyllus L.) is a popular cut-flower through- out the world (Roychowdhury and Tah, 2011). It is preferred to other cut flowers in several exporting countries as it lasts longer after being cut, has a wide range of attractive forms and colours, has the ability to withstand long distance transportation and significant ability to rehydrate after con- tinuous shipping (Salunkhe et al., 1990; Kanwar and Kumar, 2009; (*) Corresponding author: nnari26@gmail.com Citation: NIYOKURI A.N., NYALALA S., MWANGI M., 2018 - Residual effects of bioslurry and amino acids plant biostimulant on carnation (Dianthus caryophyllus L.) flower quality. - Adv. Hort. Sci., 32(1): 137-142 Copyright: © 2018 Niyokuri A.N., Nyalala S., Mwangi M. This is an open access, peer reviewed article publi- shed by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distribuited under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 7 August 2017 Accepted for publication 23 October 2017 AHS Advances in Horticultural Science Short note Adv. Hort. Sci., 2018 32(1): 137-142 138 Renukaradya et al., 2011). Although it is indigenous to the Mediterranean region, carnation can be grown in almost every cli- mate in glasshouses, plastic houses, and shade nets as well as in open field (Aydinsakir et al., 2011). It was fourth among the top ten imported cut flower to t h e N e t h e r l a n d s a f t e r r o s e s , S t J o h n ’ s w o r t (Hypericum spp.) and gypsophila with a turnover of €18 million (FloraHolland, 2017). It was also one of the main cut flowers exported by Kenya in 2012 (CBI, 2013) and among the leading cut flowers locally used in flower arrangements and in value addition of flow- ers, in form of bouquets. In 2014, carnations con- tributed 4% of the domestic value of floriculture in Kenya (HCD, 2015). The quality of carnations is currently affected by many problems such as calyx splitting and short stem length for some varieties. To meet the required quali- ty parameters such as stem length and girth, flowers size and number, farmers resort to heavy application of inorganic fertilizers and synthetic plant growth regulators. Although this results in increased produc- tion and quality, it adversely affects soil productivity and the environment. This is because pesticides, phosphorus and nitrate used in carnation production represent the major agricultural pollutants that threaten the environment (Nardi et al., 2016). With the increasing relevance of social and envi- ronmental standards, current research is focusing on developing alternative systems in crop production through development of unconventional and non- pollutant solutions. Currently, there are limited organic alternatives to meet plant nutrients. More- over, organic alternatives for plant growth regulators are lacking in many crops and limited in other crops such as carnations. Use of compost derived from plants and/or ani- mal wastes as soil amendment or fertilizer additive has been reported as an alternative in the production of several ornamental plants. Moreover, bioslurry, the residual manure generated through anaerobic decomposition of various organic materials is consid- e r e d a q u a l i t y o r g a n i c f e r t i l i z e r ( I s l a m , 2 0 0 6 ) . Similarly, the use of biostimulants in sustainable agri- culture has been growing particularly for their capaci- ty of enhancing nutrition efficiency and stress response (du Jardin, 2012). Biostimulants can be obtained from different organic materials and include complex organic materials, humic substances, beneficial chemical elements, peptides and amino acids (protein hydrolysates), seaweed extracts, inor- ganic salts, chitin and chitosan derivatives, antitran- spirants, amino acids and other N-containing sub- stances (du Jardin, 2015; Nardi et al., 2016). Many studies (Karki, 2001; Islam, 2006; Shahbaz, 2011; Jeptoo et al., 2013; Shahariar et al., 2013) reported yield increases and quality improvement on many crops such as Okra (Hibiscus esculentus L.), maize (Zea mays), cabbage (Brassica oleracea var. capitata) and carrot (Daucus carota) following bioslurry application. Studies by Nahed et al. (2009 a, b), Paradiković et al. (2011) and Mondal et al. (2015) reported that plant biostimulants could be success- fully used in the production of ornamental and other horticultural crops such as Antirrhinum majus, Gladiolus (Gladiolus grandflorum L.) sweet yellow pepper (Capsicum annuum L.) and Eustoma grandi- florum. H o w e v e r , m a n y s t u d i e s o n l y e v a l u a t e d t h e bioslurry and biostimulant direct effects, whereas there are only a few studies which focused on their residual effects on the quality and yield of many crops including carnations. This study was therefore aiming at evaluating residual effects of bioslurry and plant biostimulant on flower quality in carnation plants which previously received applications of bioslurry and plant biostimulant. 2. Materials and Methods Experiment location The study was conducted in a greenhouse at Lemotit flower farm of Finlays Horticulture Kenya Ltd. situated in Kenya at latitude 0o 22’ South and lon- gitude 35o 18’ East, from March to September 2015. Experimental design and treatments application Carnation ‘Walker’ plants planted on soil media at a density of 36 plants per m2 were used. These plants had received drench applications of bioslurry and plant biostimulant, four times at bi-weekly intervals after pinching (three weeks after transplanting) dur- ing the period September 2014 to February 2015. The experimental design was a split-plot design with three replications. The main plot measured 5.5 x 1 m (5.5 m2) while the sub-plot was 1 x 1 m (1 m2). Buffer zone of 0.5 m and 1 m separated inter-plots and indi- vidual main blocks respectively. Cow dung bioslurry was applied in main plots at the rate of 0.125, 0.25, 0.5 L m-2 and control diluted in one litre of water prior to application. Rates of plant biostimulant used were 2.0, 2.5 and 3.0 L ha-1 and control thoroughly mixed with water at the rate of 5000 L ha-1 and they Niyokuri et al. - Residual effects of bioslurry and amino-acids on carnation flower quality 139 were applied to the sub-plots during the period of September 2014 to February 2015. Bioslurry used had at wet basis a pH of 7.44, 0.23% of N, 4.58 ppm of P, 89.3 ppm of K, 4.31 ppm of Ca, 19.91 ppm of Mg and density of 1.0195 kg L-1. The plant biostimulant used was Hicure®, an amino acids based plant biostimulant. This plant biostimu- lant contains a balanced mixture of free amino acids (with higher proline and glycine contents) and pep- tides (hydrolysed protein) of natural origin. It is com- posed of amino acids and peptides (62.5%), total nitrogen (10.9%) and organic carbon (29.4%). After harvest in February 2015, carnation plants were allowed to grow for subsequent season in order to study the residual effects of bioslurry and plant bios- timulant. Maintenance practices All treatments benefited from a weekly application of mineral fertilizers through fertigation using: 3.06 g N, 3.51 g P205, 5.19 g K20, 1.71 g Ca and 0.74 g Mg, plus trace elements per square metre. Routine crop management practices included irrigation, support- ing, weeding, training, disbudding and pest manage- ment. Harvesting was done at the paint brush stage when petals started to elongate outside the calyx. Data collection and analysis Data were collected from 10 tagged sample plants per sub-plot on three flower quality parameters namely the length of flower stalk, diameter of flower stalk and flower head size (diameter and head length). The length of flower stalk was measured in centimetres from the point just below the bud to the point of origin of branch on the main stem at har- vest; diameter of flower stem was measured in mil- limetres using digital vernier callipers. The flower head length was recorded in millimetres from the point just below the calyx to the upper point of the flower while the flower head diameter was recorded in millimetres at harvesting from each harvested cut flower at paint brush stage using digital vernier cal- liper. All data were subjected to analysis of variance (ANOVA) using GENSTAT 14th Edition. Separation of means was performed using the Tukey’s Honest Significant Difference (HSD) test at P≤0.05. 3. Results There was no significant residual effect of bioslur- ry on measured parameters (Table 1). However, a significant residual effect of plant biostimulant on plants which had received any level of plant biostim- ulant was observed on flower stalk length and flower stalk diameter (Table 2). Carnations plants that had received 2.0, 2.5 and 3.0 L of plant biostimulant had significantly longer flower stalks and significantly thinner flower stalks compared to the control (Table 2). The application of different rates of plant biostim- ulant did not show a significant residual effect on flower head size (diameter and head height) as pre- sented in table 2. The interaction between different levels of bioslurry and those levels of plant biostimu- lant had no significant residual effects on measured parameters (Table 3). 4. Discussion and Conclusions Results of this study showed a significant increase of flower stalk length as a result of the residual effect of plant biostimulant. This increase of flower stalk length may be as a result of enhancement of macro nutrient uptake by plant biostimulant (Calvo et al., 2014; Rose et al., 2014) which rapidly improves the growth compared to treatments without plant bios- timulant. The other probable reason would be the direct uptake of amino acids which are immediately used by carnation plants for their growth and devel- Table 1 - Residual effect of bioslurry on carnation flower quality Bioslurry levels (L m-2) Flower stalk length (cm) Flower stalk diameter (mm) Flower head diameter (mm) Flower head length (mm) 0 81.01 5.52 21.77 40.58 0.125 81.18 5.56 22.04 40.44 0.25 81.02 5.55 21.86 40.56 0.5 81.15 5.55 21.81 40.48 Table 2 - Residual effect of plant biostimulant on carnation flower quality Levels of plant biostimulant (L ha-1) Flower stalk length (cm) Flower stalk diameter (mm) Flower head diameter (mm) Flower head length (mm) 0 80.12 b* 5.628 a 21.97 40.53 2 81.20 a 5.512 b 21.83 40.47 2.5 81.20 a 5.515 b 21.74 40.58 3 81.84 a 5.528 b 21.93 40.48 * Means in the same column with the same letter are not signifi- cantly different at P≤0.05 using Tukey’s HSD test. Adv. Hort. Sci., 2018 32(1): 137-142 140 opment (Calvo et al., 2014). There are strong evi- dences that the increase in flower stalk length may be attributed to residual auxins and gibberellins like activities of the plant biostimulant (Brown and Saa, 2015). In fact, both auxins and gibberellins are impor- tant in plant cell division and elongation (Ertani et al., 2009; Calvo et al., 2014 and Colla et al., 2014). Results of this study are in agreement with previous findings by Ertani et al. (2009) and Colla et al. (2014). Colla et al. (2014) reported an increase in coleoptile elongation rate when compared to the control, in a dose-dependent fashion, comparable with the effects of indole-3-acetic acid following the treat- ment of maize with the protein hydrolysate. The same study provided additional evidences of a gib- berellin-like activity of protein hydrolysate when application of plant-derived protein hydrolysate “Trainer” at all doses significantly increased the shoot length of the gibberellins deficient dwarf pea plants by an average value of 33% in comparison with the control treatment. Similar results previously reported by Ertani et al. (2009) showed that the treatment of lettuce with both protein hydrolysate based fertilizers resulted in an increase in the epi- cotyl length comparable with the effects of exoge- nous gibberellic acid. The occurrence of this residual effect was perhaps the result of previous down-regu- lation mechanisms which affected the effect of plant biostimulant in the previous season. Ammonium, which was used as a source of nitrogen, has been reported to down-regulate amino acids (Henry and Jefferies, 2003 cited by Gioseffi et al., 2012; Thornton and Robinson, 2005 cited by Gioseffi et al., 2012). The observed reduction in flower stalk diameter is suspected to be a gibberellin-like activity which pro- moted the flower stalk length (Ertani et al., 2009; Colla et al., 2014) at the expense of flower stalk diameter. The absence of residual effect of plant biostimu- lant on flower head size was possibly due to constant supply of nutrients through fertigation. The flower head size is usually a result of carbohydrates stored for subsequent growth and reproductive processes (Islam et al., 2010). Although there are evidences that biostimulants can enhance macro nutrient uptake (Calvo et al., 2014; Rose et al., 2014), it is pos- sible that the residual effect of plant biostimulant was limited to stimulating the elongation of flower stalk. Hence, the residual effect may have con- tributed much during early stages when carnation plants started re-growing after the harvest by improving growth and nutrients assimilation as previ- ously revealed by Colla et al. (2014). Bioslurry did not show any significant residual effect on the flower stalk length, flower stalk diame- ter and the flower head size. Generally, nutrients in cow dung slurry and poultry manure slurry are released in higher amounts compared to their origi- nal state (Haque et al., 2015). This is because bioslur- ry, with its narrower C:N than farmyard manure, shows better results on soil nutrient availability at early stages of its application while, farm yard manure affects the nutrient uptake to the plant in more consistent manner because its mineralization occurs at later stages (Muhmood et al., 2014). However, results of our study are not in agreement with Shahzad et al. (2015) who reported that the application of bioslurry and composted poultry manure as a bio-fertilizer improves soil organic mat- ter contents and availability of soil nutrients (N, P and K) to the subsequent crop, resulting in increased crop productivity and reducing the cost of fertilizer to subsequent crop. In fact, the residual effect of bioslurry may depend on its initial content, charac- teristics and the quantity applied and for these rea- sons, the residual effect of bioslurry on carnation grown in the following season was very limited. Based on results of this study, we can conclude that the application of plant biostimulant on carna- tions plants supplied with a full dose of inorganic fer- Table 3 - Residual effects of the interaction of bioslurry and plant biostimulant on carnation flower quality Bioslurry levels (L m-2) Level of plant bio- stimulant (L ha-1) Flower stalk length (cm) Flower stalk diameter (mm) Flower head diameter (mm) Flower head length (mm) 0 0 79.94 5.57 21.81 40.61 2 81.07 5.48 21.74 40.57 2.5 80.83 5.51 21.71 40.45 3 82.21 5.51 21.8 40.70 0.125 0 79.75 5.65 22.13 40.55 2 81.30 5.53 21.81 40.46 2.5 81.68 5.51 21.79 40.67 3 81.97 5.56 22.44 40.08 0.25 0 80.28 5.67 22.06 40.49 2 81.14 5.52 21.95 40.50 2.5 80.85 5.50 21.76 40.60 3 81.82 5.51 21.69 40.64 0.5 L 0 80.52 5.61 21.88 40.47 2 81.29 5.52 21.84 40.35 2.5 81.44 5.55 21.7 40.58 3 81.35 5.53 21.81 40.41 Niyokuri et al. - Residual effects of bioslurry and amino-acids on carnation flower quality 141 tilizers may have residual effect on the subsequent production flush. 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