Wood Ash as a Corrective and Fertilizer in Safflower Crop in Oxisol of Brazilian Cerrado

This study aimed at estimating the wood ash as a corrective and fertilizer in the safflower crop. This study was done with respect to the development, growth, and production of safflower in response to the wood ash doses applied to Oxisol of the Brazilian Cerrado biome. Adopting the completely randomized design and using five wood ash doses (0, 8, 16, 24, 32 g dm) and six replicates, the experiments were performed under greenhouse conditions. Each experimental unit included a 2 dm pot, filled with soil that had been incubated earlier for 30 days. The variables studied included soil pH, plant height (cm), stem diameter (mm), number of leaves (plant), SPAD index, internal and external diameters of the chapters (cm), number of chapters (plant), chapters dry mass (g pot), shoot dry mass (g pot), volume (cm pot) and root dry mass (g pot) Analysis of variance and subsequent regression test were performed for all the data using SISVAR software, at 5% probability for both. The variables internal and external diameter of the chapters and root volume showed no significant differences. The soil pH revealed a significant effect of the wood ash application tending towards linearity, as did the other vegetative variables of plant height, stem diameter, number of leaves and SPAD index. The productive constituents exhibited improved development when the wood ash was applied to the soil in doses of around 24 g dm or more.


Introduction
Safflower, with Asia and Africa being the centers of origin, has a long history of domestication since 2000 BC and was principally utilized as a yellow food and textile dye (Chapman et al., 2010).Its rural character is warranted, particularly due to its deep root system, which enhances the tolerance level of this plant under water-deficit conditions (Hojati et al., 2011).In cases of no-tillage systems, when crop rotation is required, and particularly in those cultivars highly suitable as a second crop, safflower provides a viable substitute in these production systems (Goedert et al., 2002;EMBRAPA, 2013).
To sustain and optimize the maximum productive potential, fertilizers were introduced to raise or at least maintain the yield of the agricultural systems.Issues like water table contamination, and absence of phosphate and limestone reserves, are matters of concern.In such scenarios, the application of agroindustry-generated solid waste can be a more sustainable substitute and has been producing remarkable results in the literature (Fixen, 2009;Pantano et al., 2016).Organic fertilizers have found use when combined with or even completely independent of the mineral fertilizers.Thus, the ashes arising from a combustion process that lacks any type of temperature and oxygen controls produce a residue with an abundance of calcium, magnesium and potassium carbonates (Osaki & Darolt, 1991).Besides neutralizing the soil acidity, it also supplies the soil with nutrients.Most often, such waste does not end-up at the right place and is dumped in undesirable sites.

Overview and Experimental Design
The experiments were carried out under greenhouse conditions in the Federal University of Mato Grosso, Campus of Rondonópolis, with the coordinates of latitude 16°28′150″ S and longitude 50°38′08″ W at an altitude of 284 m.During the experimental period, the mean air temperature and relative humidity were 27 °C and 81%, respectively.Employing the completely randomized experimental design, application of five wood ash doses (0, 8, 16, 24 32 g dm -3 ) and six replicates were done.Each experimental unit included a 2 dm 3 pots which were filled with soil drawn from a layer 0-0.20 m deep, in a region supporting the Cerrado vegetation.The soil was gathered from an area characterized by Oxisol (EMBRAPA, 2013;Soil Survey Staff, 2014).
The soil was gathered and incubated in plastic bags after adding in the specific wood ash doses needed for each treatment.Post incubation, the soil was watered and maintained at 60% of the maximum water retention capacity of the soil and incubated for a 30-day period.The wood ash used originated from food industry boilers.The wood ash was analyzed for its action as a fertilizer (Osaki & Darolt, 1991).The following chemical characteristics were identified: pH = 10.7;PN = 28%; N = 0.3%; P 2 O 5 = 0.9%; K 2 O = 3.4%; Ca = 3.3%; Mg = 2.1%; SO 4 = 0.4; Si 27.4%; Mn = 0.04%; B = 0.01%; Fe = 1.03%;Cr = 7.98 mg kg -1 ; As = 0.21 mg kg -1 and bulk density of wood ash was 0.45 Mg m -3 .

Experimental Units and Fertilization
After incubating the soil plus wood ash, this mixture was transferred from the plastic bags to the pots of the experimental units and conditioned.In each pot, ten seeds were sown, and thinning was done at 7 and 15 days after plant emergence until a final population of three plants per pot was reached.As the wood ash nutrient content of the plant was low, no fertilizer was applied except for nitrogen.With urea as the source, the nitrogen was applied in a 150 mg dm -3 dose.This experiment was performed using three different applications of nitrogen, at 15, 30 and 45, days after plant emergence to meet the needs of the plant (Bonfim-Silva et al., 2015b).

Response Variables
Plant height was measured in centimeters, from the plant collar at the soil level to the apex, while stem diameter was measured where the transverse measurement of the stem was taken at 2 cm height, and number of leaves was recorded by counting, with values recorded in units per plant.Using a chlorophyll meter (SPAD-502) the relative chlorophyll content (SPAD index) was noted in the two leaves of the middle one-third randomly selected from each plant, and calculating the average, later.The external diameter of the flowers and the transverse measurement of the corolla of the chapters were assessed in millimeters, utilizing a digital caliper, and finally, the numbers of chapters and branches per plant were recorded.
At this time, as most of the pots already contained at least one fully opened chapter, the safflower plants were cut.Plant cutting was performed close to the soil level and the chapters were manually separated from the other aerial parts.After placing them in paper bags they were transported to the greenhouse and subjected to forced air circulation at 65 °C for 72 hours.Once they were dried, the plant material was weighed, and the dry mass of both the shoot and chapters was ascertained.
The root volume was assessed in cm 3 .The roots were first washed in a sieve, and their volume was measured in a graduated cylinder by difference was the volume of roots.Next, the roots were packed in paper bags, identified and oven dried, adopting the same procedure used for the aerial parts.

Statistical Analyzes
Once the data were collected, the findings were submitted to statistical analysis using the SISVAR statistical program (Ferreira, 2011), with the analysis of variance and regression test being done at significance level-up to 5% probability.Brazilian-mogno (Swietenia macrophylla King) was cultivated in Oxisol, the stem diameters revealed the highest values.

Wood ash fertilized w
The SPAD index exerts an indirect effect on the chlorophyll content of the leaves depending upon the green color seen; the darker the leaves, the higher the chlorophyll concentration and, therefore, the greater the value of the index (Gil et al., 2002).
The SPAD reading is positively related to the chlorophyll content and directly linked to the nitrogenous nutrition of the plant, because of the correlation between the chlorophyll index and nitrogen content of the leaves (Costa et al., 2008).When the wood ash is applied to the soil it improves the nitrogen uptake, which may be linked to the magnesium and potassium supplied by this residue (Megda & Monteiro, 2010).Magnesium plays a crucial part in the photosynthetic process, as it is a principal ingredient in the chlorophyll molecule (Hermans & Verbrudgen, 2005;White & Broadley, 2009).
According to Dordas and Sioulas (2009) from their assessment of the response of the safflower plants to the nitrogen doses applied, the chlorophyll index showed an increase in all three cultivars, when a 200 kg ha -1 nitrogen dose was applied, as well as a higher nutrient accumulation in the grains and aerial plant parts.
The findings from the current work correspond with those of Bonfim-Silva et al. (2017b).They determined the performance of safflower in response to the phosphorus doses applied, and confirmed similar findings, with quadratic and linear responses at 30 and 45 days after emergence, respectively.Thus, it is evident that it is not the nitrogen alone which influences the index, but the quantity of the other elements presents as well, like phosphorus, potassium, and magnesium, which can cause changes in the chlorophyll activity in the plant, and thus, alter the index.
In their study on safflower genotypes of different soil bulk density levels, Paludo et al. (2017) recorded that the more the number of branches, the higher the number of chapters.They could thus establish a relationship between the number of branches and production of chapters in the plant, apart from a rise in the dry matter of the aerial plant parts.
Bonfim-Silva et al. ( 2018), on assessing the response of the Mombasa grass raised in the Oxisol, as done in the current work confirmed the quadratic behavior for the variable number of tillers of the forage, for the wood ash dose of 25.78 g dm -3 .This finding is almost identical to the results of the present study for branches in the safflower plants.Considering this, the highly improved output in the number of tillers (in comparison to the control treatment without fertilization) is due to the higher nutritional state of the plant, as it is easier for it to express its potential than with the chemical restriction (Kerbauy, 2005).
Bonfim-Silva et al. (2017b) confirmed the phytometric characteristics of the safflower plants raised in the Oxisol on phosphorus doses.The 57.1% linear escalation in the number of plant chapters concurred with the findings of the present study.Normally, when a plant develops with suitable nutritional levels, its vegetative development improves and thus, the greater will be the number of reproductive structures (Ribeirinho et al., 2012).
The highly improved performance of shoot dry mass and therefore that of the safflower chapters occurred due to the abundant availability of phosphorus, potassium, calcium, and magnesium the plant nutrients present in the wood ash, as well as micronutrients.In this study, potassium is found to exert a direct effect on the respiration and transpiration processes in the plants, controlling the stomatal opening and closure and thus, this nutrient present in sufficient quantities increases the plant efficiency in the usage of water and, hence, in better vegetative development (Taiz & Zeiger, 2004).
According to Uchôa et al. ( 2011), from their assessment of the sunflower genotypes using potassium fertilizers, reported maximum achene yields of 80 kg ha -1 .Bonfim-Silva et al. (2015a, 2017a, 2017b) also observed similar findings in their evaluation of the ornamental sunflower, Vigna unguiculata and Canavalia ensiformis, respectively, reported an escalation in the aerial plant parts in the order of 50, 93 and 66%, respectively, for the shoot dry mass plant parts cultivated in soil supplied with nearly 20 g dm -3 of wood ash doses, in comparison with the control treatment.Bonfim-Silva et al. (2013) in their assessment of the development in Marandu grass in response to the wood ash doses, confirmed that the root dry mass was inclined to rise as the wood ash doses were applied.According to these authors, the more highly improved performance of the dry mass of the plant roots is an effect of the presence of nutrients like phosphorus, which under the soil pH conditions of the control treatment was largely unavailable to the plant.Besides correcting the soil pH, the wood ash also made this nutrient available to the plant.In fact, the wood ash itself also contains substantial quantities of phosphorus, which induces this response (Monteiro et al., 1995;Sousa & Lobato, 2002;Raij, 2011;Islabão et al., 2014).
The plant responses to the wood ash applied is dependent upon many factors.The wood ash quality itself is affected by the original material from which it is made, besides the process it undergoes.The variables like initial soil fertility, organic matter, and soil type also exert a direct influence on the growth and development of the plants supplied with the wood ash doses, besides the water regime provided.Apart from this, there are many advantages of utilizing the plant wood ash for several crops both as a soil conditioner as well as a fertilizer, and its potential use is particularly evident in the recovery of degraded areas.

Conclusion
The wood ash was found to act as an effective fertilizer by correcting the soil pH.The safflower plant development and growth were positively affected by fertilization with wood ash applied to the soil.The internal and external diameters of the chapters and root volume, no significant differences were found.
The wood ash doses applied positively affected the productive constituents enabling maximum performance when the soil was fertilized with doses exceeding 24 g dm -3 .

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Figure 8. S