Impaginato 157 Adv. Hort. Sci., 2020 34(2): 157­166 DOI: 10.13128/ahsc­7775 Different environments and doses of controlled­release fertilizer in peach rootstocks production R.D. Menegatti (*), A.G. Souza, V.J. Bianchi Department of Botany, Institute of Biology, Federal University of Pelotas, RS, Brazil. Key words: fertilization, plant nutrition, Prunus persica. Abstract: The objective of this study was to evaluate the effects of different environments and doses of controlled­release fertilizer (CRF) on the initial growth of peach rootstocks [Prunus persica L. (Batsch)] cv. Capdeboscq. The experimental design was completely randomized, in a 2 x 4 factorial design, four replications and five plants per plot. The treatments were the combination of two cultivation environments (on open­air benches and greenhouse bench­ es) and four doses of CRF (0, 2, 4 and 8 g L­1 of substrate), in the 19­06­10 NPK formulation. Ninety days after their transplanting, the variables plant height, stem diameter, number of leaves per plant, shoot dry matter, root dry matter, total dry matter, plant height and stem diameter ratio were evaluated in addi­ tion to the Dickson Quality Index. All morphological variables evaluated pre­ sented a quadratic positive response to the increase of the applied fertilizer until the dosage of maximum technical efficiency (around 6.2 g L­1). The mainte­ nance of the plants in greenhouse benches and the incorporation of 4 g L­1 CRF to the substrate ensures greater efficiency in the input use, reducing the amount of time necessary for peach trees cv. Capdeboscq to achieve their graft­ ing point and to be used as rootstocks. 1. Introduction Southern Brazil is the greatest national peach producer and this region is recognized as one of the main production centers of stone fruit trees in the country, especially peach trees. However, the traditional production system of these species is mostly performed in the field (Bianchi et al., 2014; IBGE, 2018), strongly influenced by climatic conditions. The use of protected environments is an alternative for the production of stone fruit trees, which can ensure the survival of the plants during the most critical phase of the tree production chain. Especially in rootstock production by seeds, the seedlings emergence stage and initial growth require environment control, as well as optimal nutrition and irrigation, and protection against pests and diseases in order to assure the fast growth and development of the plants (Souza et al., 2017). The production of fruit plants in protected environments, such as (*) Corresponding author: renata.d.menegatti@gmail.com Citation: MENEGATTI R.D., SOUZA A.G., BIANCHI V.J., 2020 ­ Different environments and doses of controlled‐ release fertilizer in peach rootstocks production. ‐ Adv. Hort. Sci., 34(2): 157­166. Copyright: © 2020 Menegatti R.D., Souza A.G., Bianchi V.J. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed 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 3 January 2020 Accepted for publication 1 April 2020 AHS Advances in Horticultural Science http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ Adv. Hort. Sci., 2020 34(2): 157­166 158 greenhouses, allows the maintenance of optimum conditions for cultivation throughout the year, antici­ pating and extending the grafting period, reducing production costs and increasing the plants quality standard for sale (Oliveira et al., 2017). In Brazil, the traditional production system of stone fruit trees requires 360­540 days to grow a plant that is suitable for trading (Mayer et al., 2015). In this system, the necessary time for rootstocks to reach the grafting point is of approximately 240 days (Fischer et al., 2016). In part, this long period is due to the slow growth of plants in the field during the winter and early spring. In order to reduce the time between seed germi­ nation and the production of rootstocks suitable for grafting, the cultivation in a protected environment, as well as the use of appropriate substrates and fer­ tilizers in the proper doses for the crop are alterna­ tives to optimize the initial phase of the plants growth (Bianchi et al., 2014; Jamal et al., 2017; Menegatti et al., 2019 b). The environmental conditions of the plant pro­ duction system directly influence the plants physio­ logical processes and can directly affect plants growth (Souza et al., 2017). Protected environments can promote greater uniformity for the plants growth in comparison with plants produced in the field or in an unprotected environment (Reis et al., 2010; Fischer et al., 2016; Oliveira et al., 2017). Different environments can also affect the germination of seeds, and the growth and quality of the seedlings produced. The interaction between environmental conditions with the application of fertilizers may con­ tribute to optimize the space for plant production in nursery and to reduce the plant production systems impact on the environment. In addition to the use of commercial substrates, the increase of the nutrient supply is recommended b e c a u s e t h e s u b s t r a t e a l o n e d o e s n o t p r o v i d e enough nutrients for the complete development of the plants (Dutra et al., 2016). Among the many types of fertilizers available, the controlled­release fertilizer (CRF) is the most efficient. CRF promotes the slow release of nutrients and the absorption of the ideal amount throughout the plants’ growth period, a l l o w i n g t h e m t o a c h i e v e m a x i m u m s t r e n g t h (Zamunér Filho et al., 2012; Menegatti et al., 2017 a). The concomitant use of fertilizers with the sub­ strate favors the formation of more vigorous plants in shorter time, which reduces the period in which they stay in the nursery and, consequently, the pro­ duction costs (Muniz et al., 2013; Menegatti et al., 2017 b). However, few are the researches that report the use of fertilization as an additional factor to the production of stone fruit trees (Zhang et al., 2014; Jamal et al., 2017; Menegatti and Bianchi, 2019). Even scarcer are the studies that consider plant prop­ agation in a protected environment, such as a green­ h o u s e i n c o m p a r i s o n w i t h o p e n e n v i r o n m e n t s (Picolotto et al., 2007; Reis et al., 2010). The scarce information about the use of con­ trolled­release fertilizers in the production of peach rootstocks in protected environments encouraged the accomplishment of this study, whose objective was to verify the effect of different environments and doses of CRF on the initial growth of peach trees cv. Capdeboscq for rootstock purposes. 2. Materials and Methods Ripe peach fruits of cv. Capdeboscq were harvest­ ed in January 2017 from clonal mother plants kept in the Germplasm Collection of peach rootstocks at the Federal University of Pelotas (UFPel), Brazil. The experiment was conducted between October (2017) and January (2018), at the Department of Botany­ UFPel, Capão do Leão, RS, Brazil, at 21° 48’ south lati­ tude, 41° 20’ west longitude and an altitude of 11 m. After the harvest of the fruits, the post­harvest management of the pits was carried out according to Picolotto et al. (2007). Then the seeds were stratified, as described by Souza et al. (2017). After the stratifi­ cation period (35 days at 7°C), the seeds were sown, 1.0 cm deep, in 72­cell polystyrene trays (114 cm3 per cell) containing a mixture of orchard soil + vermi­ c u l i t e + m e d i u m s a n d + c o m m e r c i a l s u b s t r a t e Plantmax® (1:1:1:1) as substrate, and kept in a green­ house. When the seedlings, hereinafter referred as “ p l a n t s ” , r e a c h e d t h e t r a n s p l a n t p o i n t ( 1 5 c m between collar and apex), they were transplanted into 1­liter plastic bags containing washed sand, which was used as substrate (Table 1) and whose CRF (Osmocote®) doses had the N­P­K formulation of 19­ 06­10 (4­6 months), which were previously incorpo­ rated into the sand. The experimental design was completely random­ ized, in a 2 x 4 factorial design, with two environ­ ments (on open air benches and on benches inside the greenhouse) and four doses of Osmocote® (0, 2, 4 and 8 g L­1 substrate), with four replications and five plants per replication. “Protected environment” refers to the Arco Menegatti et al. ‐ Peach rootstocks production 159 Pampeana metallic structure greenhouse model, cov­ ered with a 150­millimeter thick, low­density poly­ ethylene plastic film, arranged at the north­south direction and with the following dimensions: 10.0 m x 21.0 m and with the maximum height of 5.0 m. The benches used in the two environments were 1­meter high metallic structures, positioned at ground level. The environmental open air conditions and the ones in the greenhouse during the period of the experi­ ment are described in Table 2. Ninety days after transplantation, when 75% of the plants of one of the treatments reached the grafting point (at least 5 mm of stem diameter and 10 cm above the soil), the plants were evaluated for the variables stem diameter (SD), plant height (H) and number of leaves (NL). Based on these data, it was possible to calculate the plant height and stem diam­ eter (H/SD) ratio. The height of the rootstocks was measured using a graduated ruler, and the stem diameter was measured with a digital caliper. The plants were dried in a forced air circulation oven at 70°C for 72 hours to obtain the shoot dry matter (SDM), root dry matter (RDM) and total dry matter (TDM) per plant. The Dickson quality index (DQI) was obtained by the formula: DQI = TDM/ [(H/SD) + (SDM/RDM)], according to Gomes and Paiva (2011). The stem diameter increase (ΔSD) was obtained through the data collected every 15 days until the end of the experiment (90 days after transplanta­ tion). Possible differences between treatments were verified by analysis of variance (ANOVA). The vari­ ables that exhibited significant differences were sub­ mitted to regression analysis in order to verify the plants growth response in proportion to the CRF increasing doses in both growing environments. The data analysis was performed in the statistical pack­ age Sisvar (Ferreira, 2011). 3. Results and Discussion At the end of the experiment (90 days after trans­ plantation), the survival rate of the peach rootstock plants was of 100% for all treatments. All variables exhibited interaction (p <0.05) between the environ­ ment factors and the CRF (Osmocote®) doses (Table 3), indicating that the study of factor interaction is important to define the best condition to stimulate plant growth and development. Table 1 ­ Average chemical composition of the sand substrates used in the production of peach tree rootstocks *sand; **OM= Organic Matter; V= Base saturation; SB= Sum of Bases; CEC= Cation Exchange Capacity (CEC). Substrates OM** % V % H+Al mg dm­3 SB mg dm­3 CEC mg dm­3 P mg dm­3 K μg dm­3 Ca μg dm­3 Mg μg dm­3 Zn μg dm­3 Fe μg dm­3 Mn μg dm­3 Sand* 0.00 67.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.44 0.00 0.00 Table 2 ­ Environmental conditions: temperature (T°C), relative humidity (RH%) and global radiation (W m­²) in the two cultivation environments (in open­air benches and greenhouse benches) during the cultivation period of peach trees cv. Capdeboscq Environment Temperature (°C) RH (%) Global radiation (W m­²) Greenhouse 23.42 66.81 348.50 Open air 21.15 78.62 477.17 Table 3 ­ Summary of the variance analysis for contrasts between the environmental factors of cultivation and CRF (Osmocote®) doses for the variables stem diameter (SD), plant height (H), number of leaves per plant (NL), shoot dry matter (SDM), root dry matter (RDM), total dry matter (TDM), plant height and stem diameter (H/SD) ratio, and the Dickson Quality Index (DQI) of peach trees cv. Capdeboscq 90 days after transplantation * Significant at the probability level (p<0.01) and ** significant at the probability level (p<0.05) by the F test. Source of variation df Mean square SD (mm) H (cm) NL SDM (g) RDM (g) TDM (g) H/SD DQI Environment (E) 1 128.2 ** 1897.8 ** 56.2 ** 603.8 ** 96.9 ** 216.2 ** 474.4 ** 42.0 ** Dose of CRF (D) 3 137.7 ** 549.8 ** 109.8 ** 233.8 ** 37.9 ** 84.1 ** 103.0 ** 60.7 ** E x D 3 8.0 ** 162.9 ** 11.6 ** 70.1 ** 12.6 ** 26.9 ** 31.4 ** 3.9 * Mean 4.3 60.8 55.0 5.9 9.6 15.5 13.4 1.7 CV (%) 4.0 4.3 11.9 10.1 25.5 17.0 6.4 9.7 Mean Greenhouse 4.6 80.9 64.0 8.48 13.8 22.3 16.7 1.8 Mean Open air 3.9 40.7 46.0 3.3 5.3 8.6 10.0 1.5 Adv. Hort. Sci., 2020 34(2): 157­166 160 All morphological variables exhibited a quadratic behavior in the adjustment of the regression equa­ tions (Figs. 1, 2, 3 and 4), proving that the highest dose test results decreases the variables values, that is, increasing the fertilizer dosage allows the increase of the plants growth up to the maximum technical efficiency dose (MTED). The MTED for plant height in the protected envi­ ronment was of 6.43 g L­1, corresponding to the height of 113.8 cm, which was three times higher than the control treatment (substrate without the addition of Osmocote®) in the same environment, 90 days after transplantation (Fig. 1). The MTED for plant height in the external environment was of 5.09 g L­1, whose plants reached the height of 52.1 cm, in contrast to the 23.9 cm high of the treatment with­ out the addition of CRF (Fig. 1). Similar height growth was also observed with the application of Osmocote® in the studies performed by Silva et al. (2011) in the production of Rangpur lime rootstock [Citrus limonia L. (Osbeck)] and by Dutra et al. (2016) in the growth of Canafistula [Peltophorum dubium (Spreng.) Taub.]. However, the environments and doses tested in their studies were different of this one. The positive effects of CRF application on plant growth in different species reinforce the necessity of specific studies to enable the definition of the MTED for each species and cultivar, which may provide s u p e r i o r g r o w t h a n d e ffi c i e n c y i n t h e u s e a n d exploitation of fertilizers by the plants. The estimated MTED for the SD variable of the plants cultivated in greenhouse was of 7.29 g L­1, cor­ r e s p o n d i n g t o a d i a m e t e r o f 5 . 5 1 m m ( F i g . 2 ) . According to the current legislation of the Secretary o f A g r i c u l t u r e a n d F o o d o f R i o G r a n d e d o S u l (Ordinance 302/98), the grafting must be performed when the rootstocks reach a SD over 5 mm and a height of 10 cm from the ground. Thus, the MTED estimated for plant grown in greenhouse allows the rootstocks to reach the minimum diameter for graft­ ing at 90 days after transplantation. On the other hand, in the external environment, the plants have not reach the minimum stem diame­ ter required for grafting during the experiment, even at the highest CRF dose (Fig. 2). In peach rootstock production, it is extremely important to define the environment and the fertiliz­ er MTED to obtain the ideal SD for grafting in a short­ er period. The minimum diameter of 5 mm is used to make sure that the rootstocks phloem and xylem have greater competence to perform rapid vascular connection between the scion/rootstock (Santarosa et al., 2016), which will allow the effective transloca­ tion of the nutrients absorbed by the roots (root­ stock) to the aerial part (scion cultivar). This condi­ tion will result in a higher percentage of graft­take and growth of the grafted plants, and it will reduce the period to obtain commercial plants. Souza et al. (2013) stress the influence of the rootstock diameter to reduce the time to develop grafted plants of “Ponkan” tangerine. The plants rapid growth was obtained with the use of rootstocks with larger diameter in the appropriate cultivation conditions in the greenhouse. The best plant growth in both height and stem diameter was obtained in plants grown in a green­ house with the MTED. This suggests that the green­ house environment provided better conditions of temperature, humidity and luminosity for the plant growth. Associated with the MTED, these conditions Fig. 1 ­ Plant height (cm) of the peach plants cv. Capdeboscq, in relation to the dosage of the controlled­release fertilizer (CRF) and two cultivation environments, 90 days after transplanting. Fig. 2 ­ Stem diameter (mm) of peach plants cv. Capdeboscq, in relation to the dosage of the controlled­release fertilizer (CRF) and two cultivation environments, 90 days after transplanting. Menegatti et al. ‐ Peach rootstocks production 161 allowed the plants to reach the ideal point for rapid grafting, which is a desired aspect in the production system of peach tree rootstocks. Paricá seedlings [Schizolobium amazonicum Huber ex Ducke] grown in a protected environment also exhibited superior performance for plant height and stem diameter (Frigotto et al., 2015). These authors concluded that greenhouse cultivation significantly increases the growth variable values in comparison with external environment cultivation. The highest mean number of leaves per plant (97) was obtained with the estimated MTED (4.69 g L­1) for the plants grown in the greenhouse (Fig. 3A). As for the variable number of leaves, it was found that the plants of cv. Capdeboscq cultivated in an open sky achieved DMET higher than plants kept in a greenhouse (Fig. 3), a fact that may be related to phytosanitary problems, such as, for example, small leaf spots and necroses detected in the leaves of this treatment, during the conduction of the plant experi­ ment. These leaf damage possibly induced damage to the leaf photosynthetic apparatus, however, this damage may have been efficiently reversed through the emission and growth of new leaves. This hypothesis can be supported by the fact that, at this moment, the plant enhances the production of photoassimilates and destines most of it, the maintenance and maximization of the aerial part, m a k i n g t h i s o r g a n t h e d r a i n o f g r e a t e r e n e r g y Fig. 3 ­ Number of leaves per plant (3A), shoot dry mass (3B), root dry mass (3C) and total dry mass (3D) of peach plants cv. Capdeboscq, in relation to the dosage of CRF and two cultivation environments. demand, both to stimulate the leaf growth maximi­ zing the capture of light, as well as to boost the thic­ kening of the stem diameter ensuring the robustness of the rootstock. It should also be noted, according to the results obtained in this work, that plants grown in the open suggest that they have prioritized the increase in the diameter of the stem at the expense of growth in height, as shown in Table 4, a strategy that can increase the robustness of the plants and decrease the exposure of the aerial part, guaranteeing their survival for a longer period, as well as the maintenan­ ce of the physiological processes in this cultivation environment, which expose the plants to sudden environmental variations. The cultivation environment has a strong influen­ ce on environmental conditions, such as temperature and global radiation, parameters that are indirectly related to the efficiency of plants in terms of light absorption capacity, and later conversion to energy, as well as in the absorption and use of nutrients. A gradual production increase of shoot dry mat­ ter, root dry matter and total dry matter up to the CRF MTED was registered (Fig. 3B, 3C and 3D), regardless of the cultivation environment. However, the plants grown in greenhouse presented higher val­ ues for total dry matter. These results corroborate the effects of Osmocote® in the growth of Rangpur lime rootstocks, as reported by Scivittaro et al. 162 Adv. Hort. Sci., 2020 34(2): 157­166 (2004). They found that as controlled­released fertil­ izer doses increased, the dry matter production of the Rangpur lime rootstocks increased as well. The leaf area has not been quantified in this study. However, there are previous studies that sup­ port the increase of the number of leaves per plant is directly proportional to the growth of the leaf area (Menegatti et al., 2017 a). The greatest leaf area of plants grown in greenhouses provides greater effi­ ciency in solar energy uptake for photosynthesis and photoassimilate production, which is directly related to the nutrient supply, including nitrogen (N), present in the CRF formulation used in this study. The use of CRF in the MTED ensures the availabili­ ty and efficient utilization of N by the plants because the leaching level of N is reduced in comparison with conventional fertilizers (Zamunér Filho et al., 2012; Muniz et al., 2013). N is an essential element to the components of the photosynthetic system, such as chlorophylls, carboxylase activity/oxygenase of ribu­ lose 1.5­bisphosphate and carboxylase of phospho­ enolpyruvate (Bassi et al., 2018), thus maintaining satisfactory rates of carbon assimilation (Taiz and Zeiger, 2017) and consequently guaranteeing the production of photoassimilates that support plant growth. The CRF effects on the production of Rangpur lime plants for use as rootstocks were registered by Serrano et al. (2006) and Silva et al. (2011). They con­ cluded that the fertilizer MTED increases the vari­ ables shoot dry matter, root dry matter and total dry matter, stressing the importance of fertilization for the maintenance of the photosynthetic process in order to increase the total dry matter and conse­ quently the plants growth. The relation between plant height and stem diam­ eter (Fig. 4A) presents a balanced growth of the plants raised in greenhouses. The H/SD ratio is one of the parameters most used in the plant’s quality evaluation. Moreover, it Fig. 4 ­ Ratio between height and stem diameter and Dickson quality index of peach plants cv. Capdeboscq, in relation to the dosage of controlled­release fertilizer and two cultivation environments. Table 4 ­ Mean values of the differences between greenhouse and open air for the variables stem diameter (SD), plant height (H), num­ ber of leaves per plant (NL), shoot dry matter (SDM), root dry matter (RDM), total dry matter (TDM), plant height and stem diameter (H/SD) ratio, and Dickson quality index (DQI) of peach plants cv. Capdeboscq 90 days after transplantation Dose SD (mm) H (cm) NL SDM (g) RDM (g) TDM (g) H/SD DQI 0 0.47 10.6 4.6 0.7 1.2 1.9 1.9 0.1 2 0.35 33.4 19.8 4.1 5.8 9.9 6.3 0.2 4 0.84 51.6 38.9 7.0 11.9 19.0 8.4 0.5 8 1.11 64.9 6.4 8.7 14.9 23.7 9.7 0.5 Menegatti et al. ‐ Peach rootstocks production 163 reflects the accumulation of reserves and ensures greater resistance and adequate potential of the rootstock (Souza et al., 2013). The index considers two parameters in a single indicator, and it can be used as a guide to determine the quality of the plants. The balance of the plants growth confirmed by the H/SD ratio may have been favored by the use of CRF. The encapsulated fertilizers, such as CRF, allow the slow release of nutrients through a porous struc­ ture (Serrano et al., 2006), becoming available to the plants root system over time and according to their n u t r i ti o n a l n e e d , a v o i d i n g t h e l e a c h a n d l o s s observed in conventional fertilizers. In addition to the H/SD ratio, the DQI is a good indicator of plant quality. For its calculation, it con­ siders the plants robustness and biomass distribution balance. Therefore, the higher the value, the better the quality standard of the plants will be (Gomes and Paiva, 2011). The ideal value considered for the DQI is approxi­ mately of 2.00 (Gomes and Paiva, 2011). In our study, the highest DQI was close to 2.2 for the estimated MTED of 6.18 g L­1 in plants grown in a greenhouse. However, for the plants kept in the external environ­ ment, the highest DQI value was of 1.83 with an MTED of 5.72 g L­1, which is lower than the ideal value (Fig. 4B). Previous research from Dutra et al. (2016) and Zamunér Filho et al. (2012), in addition to the results obtained in the present study, agree with the results for all morphological variables evaluated. A quadratic positive response was obtained proportionally to the increase of the CRF doses up to the MTED (of approx­ imately 6.2 g L­1). It proves that the plant will not have higher responses if a dose higher than the MTED is applied. The ΔSD, evaluated every 15 days after the begin­ ning the experiment, is presented in figure 5. For the plants cultivated in a greenhouse, the use of the doses of 4 and 8 g L­1 of Osmocote®, incorporated into the substrate, were proven efficient for the pro­ duction of rootstocks suitable for grafting after 90 days because they presented a final SD mean of 5.1 mm and 5.5 mm, respectively. Considering the aforementioned results and the relevance of the SD variable in the production of peach rootstocks, we suggest the incorporation of at least 4 g L­1 of Osmocote® into the commercial sub­ strate and the cultivation of the plants in a green­ house. Those conditions can increase the efficiency of the fertilizer use to obtain plants that can be graft­ ed after 90 days. The effects of different environments on the pro­ duction of peach rootstocks cv. Okinawa were reported by Reis et al. (2010). They reached the ideal point for grafting after 179 days in a protected envi­ ronment. Schmitz et al. (2014), evaluating the pro­ duction of peach rootstocks cvs. Capdeboscq and Okinawa, in three production systems, reached the grafting point after 154 days. Fischer et al. (2016), researching the influence of the stratification period on wet cold in the emer­ gence and production of several peach rootstocks in the field, obtained materials suitable for grafting after 240 days. These results indicate that the use of CRF and a protected environment are promising in the shortening of the productive cycle, as the grafting Fig. 5 ­ Increase of stem diameter, over time, of peach plants cv. Capdeboscq, in relation to the dose of the CRF and two cultivation envi­ ronments (A) Open air and (B) Greenhouse. Adv. Hort. Sci., 2020 34(2): 157­166 164 rates and accelerates the respiratory metabolism, reducing the growth rate not only for SD, but for all morphological variables (Afonso et al., 2017; Bassi et al., 2018). Another factor that may have contributed to reduce the plants growth in external environment was the CRF formulation. The granules contain a homogeneous combination of nutrients and are covered by an organic resin that regulates the nutrients release proportionally to the substrates temperature and humidity (Melo Júnior et al., 2014). In addition to the high tempera­ tures, the heavy rainfall can contribute to accelerate the release of CRF nutrients, resulting in leaching losses. A c c o r d i n g t o t h e d a t a p r o v i d e d b y t h e Agroclimatology Station of Pelotas (EAPEL, 2017), between October 2016 and January 2017, the cumu­ lative rainfall reached 549 mm, with a monthly aver­ age of approximately 137 mm, concentrated in three to four days of each month. The intense and concen­ trated precipitation in a short period of time may have caused greater leaching of the nutrients present in the soil solution that had the plants in external environment, reducing the efficiency of the fertilizer use and resulting in lower values for the evaluated variables in comparison with the plants grown in a greenhouse, which did not suffer the influence of the precipitation variable. Considering the results obtained in this study, it was suggested that the control of the environment for plant cultivation provides greater efficiency in the use of productive resources (nutrients, water, tem­ perature, light and others). In addition to these fac­ tors, the use of CRF incorporated into the substrate contributes to cause precocity in the production of peach rootstocks (reduction of the period to reach the grafting point) with a high­quality standard. 4. Conclusions Considering the results obtained in this study, the cultivation of plants in a greenhouse is proposed, since it provides the best conditions for the use of CRF by the plants, and the concomitant use of the minimum dose of 4.0 g L­1 because it reduces the period to reach the grafting point to 90 days. Acknowledgements T h i s s t u d y w a s p a r ti a l l y fi n a n c e d b y t h e C o o r d i n a ti o n f o r t h e I m p r o v e m e n t o f H i g h e r point can be reached after 90 days. This outcome is probably due to the ready availability of nutrients and the maintenance of the plants under favorable environmental conditions, although these results must be validated for other cultivars of [Prunus persica L. Batsch] rootstocks with potential use in Brazil, such as cvs. Flordaguard, Okinawa and the Tsukuba series (Menegatti et al., 2019 a). The greatest ΔSD occurred between 30 and 60 days after transplantation (Fig. 5), regardless of the dose employed, which may be due to the slow releasing of the nutrients, a main characteristic of the fertilizer used, which resulted in the greater amount of nutrients available to the plants during the experi­ ment (Huett and Gogel, 2000). This result also sug­ gests that it is necessary to replace the mineral ele­ ments around 60 days after the first application in order to maintain the plants optimal growth rate. Therefore, studies to elucidate the best CRF replace­ ment period are necessary in order to ensure contin­ ued growth through the plants different develop­ ment stages. The CRF used in the production of peach root­ stocks proved to be a promising alternative in com­ parison with conventional fertilizers. The CRF slowly and continuously releases nutrients to the plant, avoiding leach losses and volatilization. Furthermore, it ensures a better use of nutrients and reduces the environmental and economic impact (especially by the nitrogen economy, which is an expensive and easily leachable element that has a great potential to pollute the environment). The negative aspect of using CRF is the higher cost in comparison with conventional fertilizers. However, the application of the MTED, with the purpose of maximizing the input use in the production of root­ stocks, has been proving to be an economically viable alternative if we consider the price increase of basic inputs. Other characteristics to be considered are the conventional fertilizers high susceptibility of leaching due to the frequency of irrigation in the nursery and the need for parcelled applications, which are driven by higher production costs (Melo Júnior et al., 2014). The lowest ΔSD presented by plants that are grown in full sunlight (external environment) can be attributed to the restriction of the ideal microclimatic conditions for the plants growth, such as solar radia­ tion, precipitation, wind and temperature. In our region, the high temperatures at full sun, which occur between October and January, may have caused thermal stress. Such conditions reduce transpiration, which consequently decreases the photosynthetic Menegatti et al. ‐ Peach rootstocks production 165 Scientiae, 5: 499­508. MENEGATTI R.D., BIANCHI V.J., 2019 ­ Características fisiológicas, nutricionais e de crescimento de porta‐ enxertos de pessegueiro submetidos a diferentes fontes e doses de fertilizantes. ­ Acta Iguazu, 8(4): 64­77. MENEGATTI R.D., GUOLLO K., NAVROSKI M.C., VARGAS O.F., 2017 a ­ Fertilizante de liberação lenta no cresci‐ mento inicial de Aspidosperma parvifolium A. DC. ­ Scientia Agraria Paranaensis, 16(2): 45­49. 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