Fertilization With Laying Hen Manure and Economic Analysis in Caesar Weed ( Urena lobata L.) Seed Production in Amazonas, Brazil

The Caesar weed ( Urena lobata L.), produces a light-colored fiber used in the textile industry for the production of sacks, fabrics, and rugs. The bottleneck in the Caesar weed production chain is the seed production. Because Caesar weed grows in a floodplain for fiber production, it does not complete its growth cycler and produce seeds. Therefore, the seeds used in the state of Amazonas come from the Brazil state of extractivism in Pará, which increases the seed costs for fiber production. It is advantageous to develop production technologies that will produce large quantities of viable Caesar weed seed on land in the state of Amazonas. Fertilizer management is an essential element to the successful crop and seed production. Laying hen manure as an organic fertilizer is one of the most accessible fertilizers for the family farmer. It is produced in large volumes at a low cost. The purpose of this research was to evaluate the impact of different doses of laying hen manure on the production of Caesar weed seeds from the perspective of an economic analysis. The experiment was a randomized complete block design with five doses of laying hen manure (0, 5, 10, 15, 20 t/ha) and four replications. Seed productivity was evaluated from the economic point of view of fertilization. A dose of 12.7 t/ha of laying hen manure is recommended for the production of 890 kg/ha of Caesar weed seeds in low fertility soil with a very clayey texture (Souza, 2012).


Introduction
Caesar weed (Urena lobata L.) and jute (Corchorus capsularis L.) are economically important because they produce fibers used mainly for making sacks, other textile products, and artisanal confections. It was in the lowland areas of the Amazon River that the commercial cultivation of Caesar weed and jute developed on a larger scale. These crops helped absorb a large portion of the labor that became idle due to the decline in rubber production. Caesar weed readily grows in the fertile soils of the floodplainsis, but it is a plant with few nutritional requirements (Souza, 2012).
Fertilizer management for seed production is one of these unused technologies in the Amazon. Organic fertilization is an affordable and efficient alternative to commercial chemical fertilizers and result in a good profit margin, because the chemical fertilizers have to be shipped at greater expense to the seed production area compared to the locally producted organic fertilizers (Bezerra et al., 2020;Bulegon et al., 2012).
Organic fertilization has several advantages compared to chemical fertilization. These advantages include improving the soil physical and biological condition, producing an economic advantage for the small rural producer, as it reduces dependence on industrialized inputs, and makes the plant less susceptible to pests and diseases, according to the trophobiosis theory (Lin et al., 2019;Natalli et al., 2020;Primavesi, 2014).
Laying hen manure is one of the most used and accessible organic fertilizers to the family farmer because it is produced in large volumes and has a low cost. In addition to savings for the farmer, the use of laying hen manure as fertilizer redirects farm waste and do not polluting soil and water resources, therefore, resulting in additional revenue and environmental conservation (Guimarães et al., 2016;Lima et al., 2016).
It is important to note that the maximum physical production (Ymax) does not correspond to the production of maximum economic efficiency. This can be understood by analyzing the classical production function, which is divided into three phases, in which (I) the marginal productivity is maximum (Pma), and the curve presents its greatest slope, meaning the maximum contribution of each additional unit of input in the total physical production, failing to add input at this stage means failing to generate profit; (II) Pma is decreasing and greater than zero, that is, decreasing increases occur, in this stage is the maximum profit; (III) Pma is negative, excess input reduces the amount of physical production (Varian, 2012;Debertin, 1986;Strassburg et al., 2014).
Thus, the use of economic parameters in scientific experiments is recommended to assist in the accuracy of the inferences made in the research. Given the above, the objective of this research was to evaluate the effect of laying hen manure doses on Caesar weed seed production from the perspective of economic analysis.

Experiment Area
The experiment was carried out at the Experimental Farm of the Federal University of Amazonas (FAEXP/UFAM), which is located at km 922 of the BR-174 highway with coordinates 2°39′ S and 60°3′ W. According to the Köppen classification, it has an Am climate, tropical, hot, and humid, with average annual temperature and rainfall of 25 to 28 °C and 2,100 mm, respectively, and relative humidity of around 84 to 90% (Dubreuil, Fante, Planchon & Sant'anna., 2018;Ribeiro et al., 1999).

Implementation of the Experiment
Initially, soil collection and analysis were carried out, later the area was prepared with one plowing and two harrowings. A sample of laying hen manure was sent to the Laboratory of Fertilizers, Correctives, and Organic Residues at the "Luiz de Queiroz" Higher School of Agriculture of the University of São Paulo (ESALQ/USP).
The fertilizer was applied at the time of sowing, in November 2020. Seeds from the municipality of Capitão Poço (Pará, Brazil) were used. The seeds were submitted to dormancy breaking treatment in water at 80 °C for two minutes, placed to dry at room temperature, and then sown 5 to 7 seeds per hole.

Experimental Design
The experimental design was in randomized blocks (DBC), with five treatments with doses of laying hen manure (0, 5, 10, 15, 20 t/ha) and four replications. The spacing used was 1.5 m between rows and 0.5 m between plants and 3 m between plots and between blocks. The border effect was taken into consideration (Bentes et al., 2017).

Experiment Management
Thirty days after sowing, thinning was performed, leaving the two most vigorous plants per hole. To stimulate the sprouting of lateral branches and, consequently, the increase in seed production, the "capação" management was carried out, which consists of apical pruning at 80 cm when the plants reached a height between 80 cm and 100 cm. Four weedings were carried out during the experiments (Dias et al., 2008).

Experiment Evaluation
The harvest was carried out in November 2021, the stems of the plants from two holes (four plants) per plot were cut with pruning shears, identified, dried in a covered and ventilated place for ten days for drying and leaf fall. After drying, only the burs of each plot were removed and the seeds were manually extracted. Productivity was calculated by weighing the seeds and the data were expressed in t/ha (Dias et al., 2008).
To determine the economic analysis of fertilization, the Production Theory was used, with the production function derived from productivity data (1); in which the dose of laying hen manure was calculated that resulting in maximum physical production (2); and maximum profit (3); as well as the average product-AP (4); the cost-C (5); and the profit-P (6) (Varian, 2012;Debertin, 1986;Strassburg et al., 2014), by the formulas: Where, Y = Production function; Y' = derivative of the production function; VMP = value of marginal product; y = amount of physical production; x = amount of input; Py = value of physical production; Px = input value. The market prices in the year 2022 were: R$ 15 for a 40 kg bag of laying hen manure, and R$ 30.00 for a kilo of seed. The values were standardized in tons to perform the calculations. The value of the real is 0.18 dollars.

Statistical Analysis
Productivity data were submitted to the normality test, analysis of variance, F test (5% probability), and regression analysis, using the ExpDes.pt package version 1.2.1 in the R Core Team software (2021). The economic analysis was performed using tables in the Excel program. Graphs were generated by an algorithm developed in Python using the Matplotlib library (Ferreira et al., 2021;Hunter, 2007; R Core Team, 2021).

Results and Discussion
The dose of 12.7 t/ha of laying hen manure was the one that led to the maximum physical production of Caesar weed seeds (Ymax), being also the dose that led to the maximum profit, resulting in a production of 890 kg/ha of Caesar weed seeds. The analysis of variance showed a significant effect of treatments with doses of laying hen manure, with a p-value lower than 0.05 (Table 1). Regression analysis for Caesar weed seed yield data with doses of 0, 5, 10, 15 and 20 t/ha of laying hen manure (EG) resulted in the equation Y = -5.3763 x 2 + 136.1358x + 27.8732 (Figure 1). n with laying ncy. This is pr n photosynthe (Prado, 2008

Conclusion
The amount of input applied to lead to maximum physical production is greater than what leads to maximum profit. However, in a scenario of low input price and high production price, the recommendation of the amount of input applied may be the one that leads to maximum physical production.
The dose of 12.7 t/ha of laying hen manure is recommended for the production of 890 kg/ha of Caesar weed seeds in low fertility soil with a very clayey texture, characteristic of most of the Amazon soils.