Influence of Organic Fertilization on Agro-morphological Traits and Mineral Nutrient Content in Bean Grains

Plant residues such as animal feed weeds and bean straws are excellent sources of raw material for the production of organic fertilizers. In view of this, the objective of this work was to evaluate the effect of organic fertilization on the agromorphological and nutritional aspects in bean grains. The experiment was implemented in the field, in a randomized block design, with three replications, in a split plot scheme, with two types of organic compound (elephant grass enriched with cattle manure) and (bean straw enriched with cattle manure) applied in six increasing doses (0.0, 33.32, 66.65, 100.00, 133.32 and 166.65%) control treatment (recommended mineral fertilization). It was possible to identify interaction between the type of compound and the doses applied only to PL. With a yield of 2.8 t ha, mineral fertilization did not differ from treatment with 0.0% organic fertilizer. The dose of 166.65% organic fertilizer increased grain yield reaching 3.8 t ha compared to 2.4 t ha obtained in the treatment with 0.0%. In addition, this treatment increased the K content in the grains. On the other hand, the application of 133.32% of organic fertilizer can be indicated for the increase in mg content in the grains.

. Precipitation (mm/day), Relative humidity (%) and Temperature (ºC) during the period from May to August 2019

Preparation of Composts
Two types of composting were formulated: the first based on elephant grass (Pennisetum purpureum Schum.), plus bovine manure and the second, composed of bean straw with the addition of bovine manure. The materials used were dried for about 30 days in shade before being used in the composters. The "leiras" was installed in PESAGRO-RIO from June to September 2018, in a flat area protected from rain, sun and strong winds, with dimensions of 1.5 m 2 .
Each "leira" consisted of alternating layers of 20 (cm) of bovine manure height (about 10 liters) with grass or bean straw. During the production process of organic compounds, the plating and temperature and humidity were monitored, determining factors for the production of quality composting (Nunes 2009). At the end of the composting process (four months), a sample was taken for chemical analysis Table 1.    Note. pH = acidity; N = nitrogen; P 2 O 5 =phosphorus; K 2 O= potassium; Ca = calcium; Mg = magnesium; C = carbon; S = sulfur; Fe = iron; Cu = copper; Zn = zinc; Mn = manganese; B = boron.

Soil Characteristics
The soil of the experimental area has flat topography and is classified as dystrophic Tb fluoric neosol, according to the Brazilian soil classification system of (EMBRAPA 1999). Ten simple soil samples were collected at PESAGRO-RIO, using a stainless probe and a depth of 0-20 (cm). Composite samples, originated from the homogenization of simple samples, were sent to the laboratory of the Federal Rural University of Rio de Janeiro (UFRRJ), in the municipality of Campos dos Goytacazes-RJ. Table 2 presents the results of the soil analysis of the experimental plot.

Fertilizer Recommendation
For the recommendation of mineral fertilization, in this study, the NT2 technological level was used: liming, fertilization, cated seeds, 200,000 plants ha -1 , and weeds up to 30 days after the emergence of DAE. Based on this assumption Chagas et al. (1999), recommends the application of 44.44 kg ha -1 of Urea in planting, along with P 2 O 5 and KCl; 66.66 kg ha -1 urea in cover 25 DAE, with moist soil; 444.5 kg ha -1 of single superphosphate and 50 kg ha -1 of potassium chloride, and should also make foliar fertilization 111 g ha -1 ammonium molybdate with 25 DAE. The application of nutrients was not necessary: Mg, S, B and Zn. For organic fertilization, the maximum recommended dose of 40 ton was used ha -1 of organic compound little humified according to Freire et al. (2013), and this dose is considered to be 100% of the recommendation.

Cultural Practices
The cultivar used in the experiment was "BRS Esplendor". Weed control was by manual weeding. Irrigation was daily in the period without rain with the aid of micro sprinklers.

Experimental Design
The experiment was implemented in the field, in a randomized block design, with three replications, in a split plot scheme, with two types of organic compound (grass enriched with cattle manure) and (bean straw enriched with cattle manure) applied in six doses (0.0, 33.32, 66.65, 100.00, 133.32 and 166.65%) control treatment (recommended mineral fertilization) according to the model: where, yijk is the value observed in the i (2nd treatment), k (2nd block) and j (2nd subplot); µ: overall average; τi is the effect of i (2nd fator A); γk is the effect of k (2nd block); eik is the residue (a) of the parcel; βj is the effect of j (2nd factor B); (τ β) ij is the interaction between the i (2nd factor A) and the j (2nd factor B); sijk is the residue (b) of the subplot.
The experimental units contained 3 planting lines with 2 m linear each, being considered for evaluation, 1 m linear axis containing 10 plants. The spacing adopted was (50 cm between lines × 10 cm between plants) in the autumn-winter crop, characterized as dry period, according to the recommended by Vieira (1968) with a density of 10 seeds per linear meter of furrow (Vieira et al., 2006).

Characteristics Evaluated
The variables evaluated were: total number of pods (TNP); total number of grains (TNG) and total weight of pods (TWP) expressed in kg, obtained by means of precision electronic scale, performed in the useful area of the plot (10 plants). The variables plant height (PH); Root length (RL) and pod length (PL) were obtained using a ruler graduated in cm. For stem diameter (SD) and pod width (PW) a digital caliper mm was used.
Leaf area index (LAI) was made using "Accupar" meter equipment configured in m 2 m -2 (Tewolde et al., 2005). The number of nodules in the roots (NNR) was analyzed through observation and counting. All these variables were obtained in the reproductive phase of common bean in the period of physiological maturation R9. The estimated grain yield (GY) expressed in kg was made ha -1 and weight of one hundred grains (W100), expressed in kg both after postharvest processing.
For the nutritional analyses in the grains, a forced air circulation greenhouse at 65 °C was used for drying the grains. Then, the samples were crushed in a Willey-type micromill. The contents of P, K, Ca, Mg, S, B, Fe, Cu, Mn, Mo, Ni and Zn were determined after digestion with HNO 3 (Peters 2005). The reading was performed in an atomic emission spectrometry device (ICPE-9000, Shimadzu).

Statistical Analyses
The variables were initially submitted to the analysis of variance homogeneity (Bartllet test) and normality (Lilliefors). Subsequently, the joint variance analysis was performed, considering the effects of compound type, concentrations, and interaction type of compound × concentrations. The computational resources of the Genes program were used to perform the analyses (Cruz, 2013).

Variance Analysis
The evaluated characteristics met the normality assumptions of error distribution p ≤ 0.05 by Lilliefors test and residual variance homogeneity p ≤ 0.05 by Bartllet's test. These results demonstrate that, in general, the mathematical assumptions required for variance analysis and subsequent studies were attended as those of (Nascimento et al., 2018;Rocha et al., 2019).
The experiment presented good experimental precision for the characteristic length of pods LP; weight of one hundred grains W100; pod width PW; root length RL and height of plants HP with coefficient of variation below 10%, while for the other characteristics, the coefficient of variation was between 10.79 and 23.22% configuring, respectively, medium and low experimental precision Table 3. In general, the types of compounds and concentrations applied influenced some characteristics p ≤ 0.05. The interaction between them had significant results only for the LP characteristic p ≤ 0.05.
The analysis of variance for the contents of mineral nutrients in grains showed good experimental precision for the contents of Cu, Zn, K, P and S with coefficient of variation below 10%, while for the other characteristics, the coefficient of variation was between 13.20 and 70.54% configuring, respectively, medium and low experimental precision Table 4. The type of compound and the concentrations applied had a statistically influence on some characteristics p ≤ 0.05. The interaction between them did not have significant results for all characteristics evaluated p ≥ 0.05. Table 3. Summary of the analysis of variance with mean squares (QM) of the agromorphological characters of common bean in response to organic fertilization and type of organic compound and NPK+Micro Note. NS = not statistically significant, by the "F" test at the 5% probability level. * = statistically significant, by the "F" test at the level of 5% probability. ** = statistically, by the "F" test at the level of 1% probability. TNP: total number of pods; TNG: total number of grains; TWP: total weight of pods; GY: grain yield; WHG100: weight of one hundred grains; PH: plant height; RL: root length; PL: pod length; SD: stem diameter; PW: pod width; LAI: leaf area index.  Note. NS = not statistically significant, by the "F" test at the 5% probability level. * = statistically significant, by the "F" test at the level of 5% probability. ** = statistically significant, by the "F" test at the level of 1% probability. B: boron; Cu: copper; Fe: iron; Mn: manganese; Mo: molybdenum; Ni: nickel; Zn: zinc; Ca: calcium; K: potassium; Mg: magnesium; P: phosphorus; S: sulfur.

Comparison of Means
The organic compound based on elephant grass with the addition of bovine manure provided means higher than the grass and manure-based compound at doses of 66.65% and 133.32% with 8.95 and 9.51 cm, respectively. The two organic compounds did not differ from each other for the other doses applied. Using grass and manure, the highest average was at a dose of 166.65% at 9.08 cm, differing only from the dose 0.0% with 7.93 cm. Already with bean straw and manure in composting, the highest mean was obtained at the dose 133.32% with 9.51 cm, differing from doses 0.0%, 33.32% and NPK+Micro with 7.86, 8.51 and 8.66 cm, respectively Table 5.  Note. Means followed by the same lowercase letter, in the column, or uppercase, in the row do not differ from each other, statistically by the Tukey test at 5% probability.
The LAI leaf area index, on the other hand, reaches its maximum performance with the application of 100% of the recommended dose in the literature, with 1.72 m 2 m -2 . NPK fertilization did not demonstrate efficiency for the characteristics TNP, TWP, GY, PH, SD, PW and LAI, since the means were similar to the treatment with 0.0% organic fertilization. It is observed that the application of 166.65% of organic compound provided the highest average total weight of PTG and W100 grains, with 0.19 and 0.0221 kg, differing significantly only from the 0.0% control Table 6.    The Mo content in the grains was higher in the treatment with application of mineral fertilizer (NPK + micro) with 38.28 mg kg -1 , 16 times higher, compared to the addition of 2/3 organic fertilizer. The different concentrations of organic fertilizer did not differ from each other for the Mo content in the grains, with an average of 7.10 mg kg -1 . It was observed that the K content in the grains was influenced by organic fertilization, where the application of 166.65% provided the highest mean with 16.71 g kg -1 not differing from the dose 0.0% and NPK+Micro. Mineral fertilization did not differ from the lowest concentrations of organic fertilizer 0.0, 33.32 and 66.65% respectively for the K content in the grains.
On the other hand, the Mg content in the grains was also influenced by organic fertilization, where the highest mean was obtained with the application of 133.32% with 3.8 g kg -1 , not differing from mineral fertilization with 3.41 g kg -1 and other treatments with organic fertilization except for the recommended dose of 100%. The general means for K and Mg were 15.35 and 2.45 g kg -1 , respectively Table 7. Table 7. Comparison between average mineral nutrient content in common bean grains in response to organic fertilizer and NPK+Micro concentrations Note. Means followed by the same lowercase letter in the column do not differ from each other, statistically by the Tukey test at 5% probability. Mo: molybdenum; K: potassium; Mg: magnesium.

Regression Analysis
Only the characteristics LARGV and IAF had a quadratic effect in response to doses of organic fertilizer p ≤ 0.05 Figure 2 A and B. Both characteristics had R 2 ≥ 80%, percentage considered ideal for the regression model to explain the performance of the characteristic evaluated in response to doses of organic fertilization. For the LARGV characteristic, the maximum extreme point was 5.14 mm and for the IAF characteristic, the maximum extreme point was 1.68 m 2 m -2 .

Discussion
The lower availability of some macros and micronutrients in the organic compound based on elephant grass plus manure explains the higher performance of the PL characteristic at a dose of 166.65%. In pod beans, the maximum pod length value was 14.47 cm applying 33.33 t ha -1 of chicken manure (Magalhães et al., 2017). Small pods are not indicated in view of the decrease in the number of grains in the accumulation of dry matter (proteins, carbohydrates and lipids) which contributes to obtaining larger grains. Grains with higher weight have the consequence of the reduction in grain yield, and the number of vegetables/plants is the character of greatest contribution to higher yield (Kurek et al., 2001).
Cattle, goat and chicken manure also linearly increased pod length (Santos et al., 2001). On the other hand, the highest performance of PL when organic compound was applied based on bean straw plus manure at a dose of 133.32% occurs especially due to the higher concentrations of macronutrients in the organic compound Table 6.
Higher PL indicates that the number of grains will be higher, possibly with lower thickness within the pods, which contributes to the increase in productivity.
According to Davari et al. (2012) the plant by efficiently using the nutrients available in the soil through the use of organic fertilization or crop residues tends to contribute to the formation of pods. The lower performance of the PW characteristic with a dose above 133.32%, is an indication that grains with lower thickness and diameter can be obtained Figure 2A. According to Magalhães et al. (2017), the highest dose of chicken manure also linearly increased the pod diameter to 10.29 mm. Galbiatti et al. (2011) state that the use of biofertilizer in the bean crop increased the leaf area to 118.53 cm 2 , while the mineral fertilization recommended in the same experiment provided leaf area of 116.11 cm 2 . These results allow us to infer that leaf fall in the reproductive phase depends mainly on the supply of organic fertilizer in the soil, which indicates a reduction in the crop cycle. According to Ribeiro et al. (2016) there is a high association between architecture and precocity of grain production. Carvalho et al. (2003), state that there is an association between chlorophyll concentration, N content in leaves and grain yield in beans.
The production of pods is an important characteristic to be considered in view of grain yield, because the higher the number of pods, or length of pods, the greater the number of grains. However, studies reveal that this does not always happen, since several factors such as environmental, genetic and nutritional favor the lower performance of any of them, or both. According to Coelho et al. (2002), the number of pods per plant showed a high correlation with grain yield in the summer-autumn season. According to Dalla Corte et al. (2010), higher grain yield was obtained with smaller seeds, through high and negative correlations between seed width and thickness.
The use of bovine manure contributed to the N content in the composting, making it indispensable for the growth of microorganisms. In future experiments, it will be possible to observe an improvement in the soil structure used, besides promoting changes in plant characteristics, especially for pod development and grain filling.
The increase in production is related to the variable pod weight Santos et al. (2014), emphasizing that both depend on the plant's ability to absorb water and nutrients. Oliveira et al. (2000) found higher pod yield at a dose of 24 t ha -1 of bovine manure. Santos et al. (2007), report that the number of grains per NGV pod, and the weight of 1,000 PS1,000 grains, were not influenced by different doses of biofertilizer applied to cowpea.
Soil conditions such as texture, moisture, pH and nutrients, in addition to the availability of photoassimilates are factors that are directly related to root growth (Peres & Kerbauy, 2000). The roots develop in the direction in which the nutrients are found in the soil (Drew, 1975), which explains the lower performance of the RL characteristic when there was no fertilization Table 6.
The organic compounds used proved to be efficient, providing the nutrients needed for absorption, strengthening what was said by Oliveira et al. (2010) that cattle manure in adequate amounts is able to supply the needs of plants with higher availability of NPK. In addition, organic compounds can provide the nutrients needed for crops and replace mineral fertilizers (Leal et al., 2007).
The improvement in porosity, retention and infiltration of water in the soil is the result of the management of organic fertilization (Rodrigues et al., 2013). Although the RL performed well with organic fertilization, it was observed that the plants did not present nodules in the roots. According to Brito et al. (2011), the reduction in symbiotic fixation of N in common bean and cowpea plants is directly related to the increase in n dose.
According to Moura et al. (2012) the number of grains per pod correlates positively with grain yield, but the negative correlation between number of grains per pod, protein content and iron content suggests that the increase in the number of grains per pod decreases the protein and iron content in the grains.
The good performance of the W100 feature is a sign that the plant is investing in grain filling which tends to contribute to the nutrient content. According to Coimbra et al. (2000), the characters number of vegetables per plant and mass of one thousand grains showed a high degree of association with grain yield. According to Correa et al. (2015) the mass of five pods and the number of grains per pod are the components that most contribute to the production of grains in cowpea, surpassing the mass of one hundred grains.

Conclusions
The addition of 2/3 of the recommended organic fertilization increased 58.31% in grain yield and 23.23% in K content in grains compared to 0.0% dose. The addition of 1/3 of the organic fertilization may be indicated for the increase in mg content in the grains, compared to the dose recommended by the literature 40 ton ha -1 .