Introduction
⌅The legume known as “mesquite” (Prosopis laevigata (Humb. & Bonpl. ex Willd.) M.C. Johnst.) is primarily found in the arid and semi-arid regions of North America. In Mexico, it is widely distributed in these regions in the northern and central states, where mesquite is utilised for forestry, agriculture, and livestock development in certain areas (Rodríguez et al., 2014Rodríguez E, Rojo G, Ramírez B, Martínez R, Cong M, Medina S, Piña H, 2014. Análisis técnico del árbol del mezquite (Prosopis laevigata Humb. & Bonpl. ex Willd.) en México. Ra Ximhai 10 (3):173-193 10.35197/rx.10.01.e.2014.13.er; Monroy-Alta & Ramírez-Saldivar, 2018Monroy-Ata A, Ramírez-Saldívar KY, 2018. Relación entre sucesión ecológica vegetal y hongos micorrizógenos arbusculares en un matorral xerófilo en el centro de México. TIP. Rev Esp Cienc Quím Biol 21: 13-2910.22201/fesz.23958723e.2018.0.157.).
This species has a considerable impact on the ecological balance due to its capacity to fix atmospheric nitrogen, thereby enriching the soil by generating organic matter that improves its fertility (López et al., 2010López JA, Ríos JC, Monárrez JC, Rosales R, Mejía JM. Bustamante V, 2010. Tecnología disponible para la obtención de semilla de mezquite en el norte de México. Campo Experimental Valle del Guadiana INIFAP, Durango, Dgo México.). It acts as a nurse plant thus promoting the growth of other plants, providing shelter for birds and rodents, reducing soil erosion and conserving wildlife (García-Sánchez et al., 2012García-Sánchez R, Camargo-Ricalde SL, García-Moya E, Luna-Cavazos M, Romero-Manzanares A, Montaño NM, 2012. Prosopis laevigata and Mimosa biuncifera (Leguminosae) jointly influence plant diversity and soil fertility of a Mexican semiarid ecosystem. Rev Biol Trop 60 (1): 87-103 10.15517/rbt.v60i1.2365.; Rios et al., 2012Ríos-Saucedo JC, Rivera-González M, Valenzuela-Nuñez LM, Trucios-Caciano R, Rosales-Serna R, 2012. Diagnóstico de las reforestaciones de mezquite y métodos para incrementar su supervivencia en Durango, México. Revista Chapingo Serie Zonas Áridas 6 (2):63-67.).
Given its extensive distribution and adaptive capacity in diverse ecological systems, mesquite is an appropriate choice for reforestation programmes seeking to reverse the damage caused by land use changes and expansion of grazing areas for livestock (Ríos-Saucedo et al., 2012Ríos-Saucedo JC, Rivera-González M, Valenzuela-Nuñez LM, Trucios-Caciano R, Rosales-Serna R, 2012. Diagnóstico de las reforestaciones de mezquite y métodos para incrementar su supervivencia en Durango, México. Revista Chapingo Serie Zonas Áridas 6 (2):63-67.). To mitigate this problem, the production of mesquite using a variety of different techniques in forest nurseries has increased in recent years(Prieto et al., 2013Prieto JA., Rosales S, Sigala JA, Madrid RE, Mejía JM, 2013. Producción de Prosopis laevigata (Humb. et Bonpl. ex Willd) en diferentes mezclas de sustratos en vivero. Rev Mex de Cienc Forestales 4(20): 50–57 10.29298/rmcf.v4i20.369.; Cervantes-Rodríguez et al., 2018Cervantes-Rodríguez N, Prieto-Ruíz JA, Rosales-Mata S, Félix-Herrán JA, 2018. Crecimiento de mezquite en vivero bajo diferentes condiciones de sustrato, riego y retenedores de humedad. Rev Chapingo Ser Cienc For Ambient 24(1): 17-3110.5154/r.rchscfa.2016.10.056.). Nevertheless, the management of this species in cultivation work remains inadequate.
A quality plant is defined as one that has a series of morphological and physiological attributes that enable it to adapt and develop in the climatic and edaphic conditions of the planting site (Rodríguez-Trejo, 2008Rodríguez-Trejo DA, 2008. Indicadores de calidad de planta forestal. Mundi-Prensa: México, D. F. México. 156 pp.). It is therefore essential to develop new methods or technologies to enable seedlings to acquire the necessary morphological characteristics such as height and stem diameter, as well as quality variables, including a balanced aboveground biomass/ belowground biomass ratio, robustness index and Dickson quality index. This will facilitate better acclimation to plantation sites (Prieto et al., 2013Prieto JA., Rosales S, Sigala JA, Madrid RE, Mejía JM, 2013. Producción de Prosopis laevigata (Humb. et Bonpl. ex Willd) en diferentes mezclas de sustratos en vivero. Rev Mex de Cienc Forestales 4(20): 50–57 10.29298/rmcf.v4i20.369.; Birchler et al., 1998Birchler T, Rose RW, Royo A, Pardos M, 1998. La planta ideal: revisión del concepto, parámetros definitorios e implementación práctica. Investigación agraria Sistemas y recursos forestales 7(1-2): 109- 12010.5424/594.). These characteristics can be induced through alternative fertilisation and substrates, thereby producing produce seedlings of superior quality (Prieto et al., 2013Prieto JA., Rosales S, Sigala JA, Madrid RE, Mejía JM, 2013. Producción de Prosopis laevigata (Humb. et Bonpl. ex Willd) en diferentes mezclas de sustratos en vivero. Rev Mex de Cienc Forestales 4(20): 50–57 10.29298/rmcf.v4i20.369.; Reyes et al., 2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.).
A variety of techniques and alternatives exist for the reproduction and development of plants in nurseries, including the use of water-retaining polymers (Palacios-Romero et al., 2017), hydrogel (López-Elías et al., 2016), biofertilizers (Aguirre-Medina et al., 2014Aguirre-Medina JF, Mina-Briones FO, Cadena-Iñiguez J, Dardón-Zunun JD, Hernández-Sedas DA, 2014. Crecimiento de Cedrela odorata L. Biofertilizada con Rhizophagus intraradices y Azospirillum brasilense en vivero. Rev Chapingo Ser Cienc For Ambient 20(3): 177-183. 10.5154/r.rchscfa.2014.01.001), and leachates (González-Castellanos et al., 2012González-Castellanos A, Milpa-Mejía S, Vázquez-García LM, Grenón-Cascales GN, 2012. Cultivo en maceta de Iris xiphium L. (Iris de Holanda) con diferentes concentraciones de humus de lombriz y sus lixiviados. Rev Fac Cienc Agrar 44 (2):109-117.) derived from compost as organic alternatives. The agroecological leachate derived from composting is employed in sustainable organic production, whereby organic waste is treated and reused as a by-product. As outlined by Granada-Torres & Prada-Millán (2015Granada-Torres CA, Prada-Millán Y, 2015. Caracterización del lixiviado agroecológico a partir de residuos orgánicos de cultivos. Revista De Investigación Agraria Y Ambiental 6 (2): 169–182 10.22490/21456453.1414.), this material can be employed as a fertiliser due to its soluble nutrient content and the presence of beneficial microorganisms (Ingham, 2005Ingham RE, 2005. The compost tea Brewing Manual. Soil Foodweb Inc Corvallis, Oregon USA. 79 p.). Moreover, it can be employed in organic production systems under greenhouse conditions (Rodríguez et al., 2007Rodríguez DN, Cano RP, Favela CE, Figueroa VU, Álvarez PV, Palomo GA, Márquez HC, Moreno RA, 2007. Vermicomposta como alternativa orgánica en la producción de tomate en invernadero. Revista Chapingo Serie Horticultura 13(2): 185-19210.5154/r.rchsh.2007.01.002.).
The term “biofertilizers” is used to describe products that are based on one or more non-pathogenic soil microorganisms. These microorganisms live in association or symbiosis with the plant root system when they are inoculated. This interaction enhances the availability of nutrients, both in terms of quantity and accessibility, thereby facilitating the growth and reproduction of annual plants. The microorganisms used as biofertilisers in Mexican agriculture are the endomycorrhizal fungi and nitrogen-fixing bacteria (Aguirre-Medina, 2006Aguirre-Medina JF, 2006. Biofertilizantes microbianos: Experiencias agronómicas del programa nacional del INIFAP en México. Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias-Centro de Investigaciones Regionales Pacífico Sur-Campo Experimental Rosario Izapa, México. 206 pp.). The objective of the present study was, therefore, to evaluate the impact of a chemical fertilizer and two organic fertilizers added to irrigation water on the morphometric variables of P. laevigata grown under greenhouse conditions for subsequent use in restoration. It is hypothesised that organic fertilisers will represent an alternative means of fertilising forest seedlings, thereby reducing the necessity for chemical fertilisers.
Material and methods
⌅Collection of biological material and seedling production
⌅In October and November 2021, fruits from five mature specimens of P. laevigata were collected at the Center for Agricultural Sciences of the Autonomous University of Aguascalientes (CCA-UAA). The seeds were subsequently manually extracted from the fruits.
The experiment was conducted in a greenhouse located at the CCA-UAA (21°58’1.23”N, 102°22’132.94”W; 1922 m.a.s.l.) from February to July. The greenhouse was oriented in a north-south direction and equipped with polyethylene plastic and 35% shade netting. The temperature and relative humidity were recorded on a hourly basis using an Extech RT10 data logger (Table 1). The seedlings were irrigated at field capacity (200 mL /seedling) three times per week following sowing, on Mondays, Wednesdays, and Fridays, during the morning hours, using a water spray gun.
The seedlings were cultivated in 380 mL interchangeable tubes using a substrate mixture of 80% peat-moss and 20% perlite. These substrates were deemed optimal for the development of the seedlings and are commonly used by producers in the area. Seed sowing was conducted on 17 February, 2022. Prior to sowing, the seeds were subjected to a 3-minute immersion in water at 80 °C, followed by a 12-h. immersion at room temperature. Seeds that did not exhibit visible imbibition were sanded to degrade the test and immersed for 24 h. To prevent fungal infection, 5 mL of Captan® (1g/L) per seed was added during sowing.
Treatments
⌅The efficacy of six treatments was assessed using three distinct types of fertilisers: one chemical and two organic fertilizers (Table 2). The chemical fertilizer employed was 19 N-19 P-19 K + M.E. (microelements) from Haifa®. The organic fertilisers were as follows: 1) Worm leachate, in commercial product form, made from fermented worm leachate and enriched with fulvic and humic acids (Table 3), and 2) Nitrogen-fixing bacteria, also in commercial product form (Table 4). A total of 50 seedlings were used for each treatment, with the seedlings distributed across two racks with 25 individuals per rack. The treatments were situated in the central area of the greenhouse in order to ensure that the seedlings were exposed to identical environmental conditions. The experimental design was implemented using a completely randomized approach. Fertilisation process was conducted on a weekly basis, with 20 mL of the designated treatment fertiliser being added to the irrigation water per plant. The exception to this was the inoculation with bacteria, which was only carried out at the commencement of the experiment and again at eight weeks after sowing. The initial inoculation of the seedlings with nitrogen-fixing bacteria treatments was conducted eight days prior to the commencement of fertilisation. The fertilisation process commenced 20 days after sowing and continued for a period of three months (Reyes et al., 2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.). One month after the commenced of fertilisation, the dosage of the fertiliser solution was increased from 20 mL to 30 mL.
Plant evaluation.
⌅At the end of the fertilizing period, 20 seedlings per treatment were randomly selected for evaluation at 131 DAS (days after seeding). Each seedling constituted an experimental replicate. The height of the aerial part of each seedling was measured using a 50 cm graduated ruler. The diameter of the basal stem was measured using a digital caliper (SURTEK® 12220). The fresh weight of the aboveground and belowground parts was measured using an analytical balance (Ohaus® SJX1502/E). Subsequently, the material was placed in brown paper bags and subjected to a 72-h. drying process at 60 °C, thereby obtaining the dry biomass of the aboveground (AGDW) and belowground (BGDW) components (Reyes et al., 2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.; Martínez-Calderón et al., 2020Martínez-Calderón VM, Sosa-Ramírez J, Torres-González JA, Mendieta-Vázquez AG, Sandoval-Ortega MH, 2020. Propagación de Forestiera phillyreoides: una especie potencial para la restauración en el Centro-Norte de México. Madera y Bosques 26(2): e262205210.21829/myb.2020.2622052.).
The robustness index (RI) of the seedlings was calculated using the obtained data:
RI = height (cm)/diameter (mm)
Aboveground dry biomass/ belowground dry biomass ratio:
AGDW/BGDW = Dry weight of the aerial part/root dry weigh
Dickson quality index (DQI):
The calculated variables were classified as high, medium, or low quality, in accordance with the criteria established by Rueda-Sánchez et al. (2014Rueda-Sánchez A, Benavides-Solorio J, Saenz-Reyez J, Muñoz-Flores H, Prieto-Ruiz JÁ, Orozco-Gutiérrez G, 2014. Calidad de planta producida en los viveros forestales de Nayarit. Rev mex de cienc forestales 5(22): 59-6310.29298/rmcf.v5i22.350.) for broadleaf species. In height, values < 12.0 are considered to be of low quality, values from 12.0 – 14.9 of medium quality, and values ≥15.0 of high quality. For diameter, values < 2.5 are considered to be of low quality, values from 2.5 – 4.9 of medium quality, and values ≥ 5.0 of high quality. Robustness index values ≥ 8 are considered to be of low quality, values from 7.9 – 6.0 of medium quality, and values < 6.0 of high quality. For the AGDW/BGDW ratio, values ≥ 2.5 are considered to be of low quality, values from 2.4 – 2.0 of medium quality, and values < 2.0 of high quality. Dickson quality index values < 0.2 are considered to be of low quality, values from 0.2 – 0.4 of medium quality, and values ≥ 0.5 of high quality.
The financial implications of fertilisation were evaluated based on the doses administered to each seedling and the associated treatment. The financial implications were calculated using fertilizer prices as recorded in the year 2022. The estimated cost of fertilization was based on the production of one million plants (Reyes et al., 2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.).
Statistical analysis
⌅The means and standard deviations (SD) were calculated for the morphometric variables obtained from the experiment. To ascertain whether significant differences existed among the treatments, the normality and homoscedasticity of the data were evaluated through the utilisation of Shapiro-Wilks and Levene tests. If the assumption of normality and homoscedasticity is valid, the means were compared using a one-way ANOVA test and Tukey's test for significant differences (p ≤ 0.05). In instances where the data did not present a normal distribution and homoscedasticity, they were transformed using square root to achieve statistical assumptions. All analyses were performed using the InfoStat software (Di-Rienzo et al., 2016).
Results
⌅The application of fertilizers in conjunction with irrigation resulted in statistically significant differences (p ≤ 0.05) in both morphological and quality variables among the various treatments (Table 5).
M. E: Microelements, RI: robustness index, AGDW/BGDW: Aboveground dry biomass / belowground dry biomass ratio, DQI: Dickson quality index, Q: quality (H: high, M: medium, L: low Mean with a letter in common are not significantly different between treatments according to Tukey test (p > 0.05; N = 120; n = 20).
Plant height differed significantly among treatments (F5,114 = 118.83, p < 0.0001) (Fig. 1, Table 5). The treatments that included chemical fertilizer (T2 and T3) exhibited the greatest height values, at 23.45 ± 3.86 cm and 28.00 ± 4.41 cm respectively, and demonstrated the highest quality in this variable. The seedlings treated with organic fertilizers (T4, T5 and T6) exhibited a medium quality, differing in this regard from the control treatment (T1), which demonstrated the lowest quality the shortest height (10.41 ± 2.02 cm).
Significant differences were also observed in diameter (F5,114 = 8.29, p < 0.0001). The treatment that combined organic and chemical fertilization (T3) exhibited the greatest diameter (2.81 ± 0.34 cm). The diameters observed in treatments T2, T4, T5, and T6 were found to be similar. In terms of quality, treatments T2 and T3 demonstrated average quality, while remaining treatments exhibited low quality.
The RI presented significant differences (F5,114= 44.02, p < 0.0001) between the treatments that received chemical fertilizer (T2 and T3) and the remaining treatments, which exhibited a lower RI. In contrast to the aforementioned variables, the treatments incorporating chemical fertilizers (T2 and T3) exhibited a comparatively inferior quality compared to the other treatments.
The AGDW/BRDW ratio showed a significant difference (F5,114 = 16.02, p < 0.0001) between the T2 and T3 treatments and the other treatments, which were found to be statistically similar. The quality obtained in this variable was predominantly high in the treatments utilising organic fertilizers, and only the exclusively chemical treatment (T2) presented a medium quality.
The DQI presented significant differences (F5,114 = 9.37, p < 0.0001). The combined organic and chemical treatment (T3) presented the highest value, followed by the exclusively chemical treatment (T2) and the treatment with beneficial bacteria (T5). In terms of quality, all treatments were found to be of low quality (Table 5).
Fertilizer costs in production
⌅Fertilizer costs per treatment differed considerably between the chemical and organic fertilizers in terms of producing one million seedlings. The cost of treatments with worm leachate was the highest. Treatment T6 was the most expensive, costing MXN 75,000, followed by treatment T3, with a cost of MXN 66,000, and treatment T4 at MXN 60,000. The least expensive treatment was exclusively chemical fertilization (T2), with an approximate cost of MXN 6,000, followed by the treatment with nitrogen-fixing bacteria (T5) at a cost of MXN 9,000.
Discussion
⌅The combination of chemical and organic fertilizers in P. laevigata demonstrated the most favourable outcomes across the evaluated variables. This phenomenon has been observed in numerous studies involving horticultural crops, where the combination of organic and chemical fertilization has been found to enhance growth and yield in crops (Tlelo-Cuautle et al., 2020Tlelo-Cuautle AM, Taboada-Gaytán OR, Cruz-Hernández J, López-Sánchez H, López PA, 2020. Efecto de la fertilización orgánica y química en el rendimiento de fruto de chile Poblano. Rev fitotec mex 43(3): 283-28910.35196/rfm.2020.3.238.; Gelaye, 2023Gelaye Y, 2023. Effect of combined application of organic manure and nitrogen fertilizer rates on yield and yield components of potato: A review. Cogent Food Agric 9 (1): 2217603 10.1080/23311932.2023.2217603.). Conversely, a study conducted on poplar (Liriodendron tulipifera L.) demonstrated that chemical and organic fertilizers, as well as their combination, presented comparable morphological values under nursery conditions (Han et al., 2016Han SH, An JY, Hwang J, Kim SB, Park BB, 2016. The effects of organic manure and chemical fertilizer on the growth and nutrient concentrations of yellow poplar (Liriodendron tulipifera Lin.) in a nursery system. Forest Sci Technol 12 (3): 137-143 10.1080/21580103.2015.1135827.).
In contrast to the present study, the aforementioned studies used soil as a substrate, which is a crucial factor in the efficiency of organic fertilizers. In soil, organic fertilizers facilitate the availability of nutrients for the plant and improve both the physical and chemical conditions of the soil (Oyetunji et al., 2022Oyetunji O, Bolan N, Hancock G, 2022. A comprehensive review on enhancing nutrient use efficiency and productivity of broadacre (arable) crops with the combined utilization of compost and fertilizers. J Environ Manage, 317: 11539510.1016/j.jenvman.2022.115395.).
Concerning plant height, the results from treatments with chemical fertilizer (19-19-19 + M.E.) and the control treatment were similar to those reported by Reyes et al. (2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.) for P. laevigata, although with a smaller diameter. In the present study, a lower fertilizer concentration of 0.5 g/L was used compared to that used by Reyes et al. (2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.), which was 1 g/L. This suggests that the species can develop adequately in terms of the variable height, achieving a high quality with less fertilization and thus making the production less expensive. The height attained is directly related to the higher concentration of nutrients, such as nitrogen, in the chemical fertilizer compared to the organic fertilizer. The lower concentration of nitrogen and other elements in the worm leachate has a direct impact on the height attained by the seedling.
The treatments inoculated with nitrogen-fixing bacteria resulted in larger sizes compared to those reported by Quiñones-Gutiérrez et al. (2013) for P. laevigata, using Azotobacter spp. and Azospirillum spp. The present study also included Rhizobium spp and Bacillus spp. These genera of bacteria have been widely used in agricultural practices with favorable results (Aguirre-Medina et al., 2014Aguirre-Medina JF, Mina-Briones FO, Cadena-Iñiguez J, Dardón-Zunun JD, Hernández-Sedas DA, 2014. Crecimiento de Cedrela odorata L. Biofertilizada con Rhizophagus intraradices y Azospirillum brasilense en vivero. Rev Chapingo Ser Cienc For Ambient 20(3): 177-183. 10.5154/r.rchscfa.2014.01.001; dos Santos Sousa et al., 2022dos Santos Sousa, W, Soratto RP, Peixoto DS, Souza T, Barros M, Vaz AG, Teixeira IR, Gitari HI, 2022. Effects of Rhizobium inoculum compared with mineral nitrogen fertilizer on nodulation and seed yield of common bean. A meta-analysis. Agron Sustain Dev 42: 52. 10.1007/s13593-022-00784-6; El-Beltagi et al., 2022El-Beltagi HS, Ahmad I, Basit A, El-Lateef HM, Yasir M, Shah ST, Ullah I et al., 2022. Effect of Azospirillum and Azotobacter Species on the Performance of Cherry Tomato under Different Salinity Levels. Gesunde Pflanzen 74, 487–499 10.1007/s10343-022-00625-2.).
Similar results were achieved through the use of chemical fertilizers, using nitrogen-fixing bacteria, specifically Rhizophagus intraradices and Azospirillum brasilense, in Cedrela odorata L. (Aguirre-Medina et al., 2014Aguirre-Medina JF, Mina-Briones FO, Cadena-Iñiguez J, Dardón-Zunun JD, Hernández-Sedas DA, 2014. Crecimiento de Cedrela odorata L. Biofertilizada con Rhizophagus intraradices y Azospirillum brasilense en vivero. Rev Chapingo Ser Cienc For Ambient 20(3): 177-183. 10.5154/r.rchscfa.2014.01.001). However, in this study and in that conducted by Quiñones-Gutiérrez et al. (2013), the desired effect was not achieved.
Soil and manure were used in the aforementioned study on C. odorata, which may have favoured the growth of bacteria. This is because bacteria present greater efficiency and growth in soils with an adequate organic matter content (dos Santos Sousa et al., 2022dos Santos Sousa, W, Soratto RP, Peixoto DS, Souza T, Barros M, Vaz AG, Teixeira IR, Gitari HI, 2022. Effects of Rhizobium inoculum compared with mineral nitrogen fertilizer on nodulation and seed yield of common bean. A meta-analysis. Agron Sustain Dev 42: 52. 10.1007/s13593-022-00784-6). It is therefore recommended that future studies use soil from the region instead of sterile substrates to promote the optimal functioning of the nitrogen-fixing bacteria.
In the present study, low formation of nodules was observed in the roots. This may be due to the bacteria used not being fully compatible with P. laevigata (Crespo-Flores et al., 2021Crespo-Flores G, Ramírez-Tobias HM, Vallejo-Pérez MR, Méndez-Cortés H, 2021. Coinoculación con rizobios y hongos micorrízicos arbusculares en plántulas de Prosopis laevigata. Rev Mex Cienc Agríc 12(7):1249-126210.29312/remexca.v12i7.2910.). It is therefore recommended that future studies be focused on isolating native bacterial species and those associated with mesquite.
The RI, AGDW/BGDW ratio, and DQI have been described as important and desirable parameters for survival and development in the field when carrying out reforestation (Birchler et al., 1998Birchler T, Rose RW, Royo A, Pardos M, 1998. La planta ideal: revisión del concepto, parámetros definitorios e implementación práctica. Investigación agraria Sistemas y recursos forestales 7(1-2): 109- 12010.5424/594.). The results of the RI analysis indicate that seedlings with a more favorable relationship between height and basal diameter are more resistant to physical damage. Furthermore, a balanced AGDW/BGDW ratio would indicate that the seedlings have a greater resistance to drought conditions, directly favoring their survival in the semi-arid regions where P. laevigata is native (Birchler et al., 1998Birchler T, Rose RW, Royo A, Pardos M, 1998. La planta ideal: revisión del concepto, parámetros definitorios e implementación práctica. Investigación agraria Sistemas y recursos forestales 7(1-2): 109- 12010.5424/594.; Martínez -Calderón et al. 2021).
The RI values were slightly higher than those reported by Reyes et al. (2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.) for the control treatment and treatments with chemical fertilization, in which 19-19-19 was also used with P. laevigata. However, the DQI values were similar to those obtained by Prieto et al. (2013Prieto JA., Rosales S, Sigala JA, Madrid RE, Mejía JM, 2013. Producción de Prosopis laevigata (Humb. et Bonpl. ex Willd) en diferentes mezclas de sustratos en vivero. Rev Mex de Cienc Forestales 4(20): 50–57 10.29298/rmcf.v4i20.369.) for this species. The treatments that did not utilize chemical fertilizers showed superior quality in terms of the RI and AGDW/BGDW ratio parameters. Plant growth differed in height in the treatments with chemical fertilizer, which was attributed to the higher nitrogen content. This is reflected in the values obtained for the RI and the AGDW/BGDW ratio.
The present study revealed differences in the results obtained from the organic and chemical treatments. This indicates that reforestation using seedlings produced in this study may yield different outcomes depending on the type of treatment employed. As a subsequent step, it is recommended that field experiments be conducted to record the survival rates of seedlings obtained from organic fertilizers compared to those obtained from conventional chemical fertilization methods. Due to the limited research on the survival rate of P. laevigata in the field, it would be beneficial to conduct studies in this area.
The costs associated with the production of one million seedlings were lower than those calculated by Reyes et al. (2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.), in which they reported chemical treatments costing up to MXN 90,000. This cost is comparable to the price of the organic fertilizer utilized in this study. The cost of the chemical fertilizer 19-19-19 + ME was found to be lower than the cost calculated in the present study when compared to the study carried out by Reyes et al. (2018Reyes GDJ, Prieto-Ruíz JA, Vazquez-Cisneros I, López-López MA, Hernández-Díaz JC, Chávez-Simental JA, 2018. Alternativas de fertilización para producir Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst en vivero. Rev Mex de Cienc Forestales 9(49): 234-25110.29298/rmcf.v9i49.175.). The cost of supplies can vary depending on the type and availability of supplies purchased, concentrations used, number of applications, quantity of fertilizer solution used per application, and the prices at the time of purchase.
The cost analysis in the present study for the production of one million seedlings presents an unfavourable outlook for the use of organic fertilizers in technical forestry production. When considering only the measured variables, the use of chemical fertilizer presents a more favorable cost-benefit balance for the producer. It is imperative that the search for sustainable and environmentally friendly options is not discouraged. Consequently, it is vital to investigate a range of alternatives and test a variety of organic fertilizers and concentrations to ensure the production of high-quality seedlings that meet the requisite parameters for reforestation. It is important to note that the use of composts was not evaluated in this study. However, it could be a viable alternative when combined with other organic fertilizers such as leachates and beneficial bacteria. To reduce costs, producers must have the capacity to produce their own organic fertilizers, which would significantly reduce fertilization costs.
Conclusion
⌅The use of the mixture of chemical and organic fertilizers achieved better results in terms of plant height (28.00 ± 4.41 cm) and diameter (2.81 ± 0.34 cm), compared to organic fertilizers. Organic fertilizers were found to enhance the RI and the AGDW/BGDW ratio. It is recommended that the survival of seedlings obtained with both chemical and organic fertilization in the field be evaluated to assess their performance during reforestation. The costs associated with organic fertilization were found to be higher than those of chemical fertilization.
To achieve larger and higher-quality seedlings, it is essential to continue experimenting with various concentrations and forms of organic fertilization. Additionally, producers are encouraged to lower production costs by making their own organic fertilizers.