Soil preparation x Crop establishment

In bean cultivation, periodic soil preparation provides several effects for its establishment, including the longitudinal distribution of seeds and the speed of seedling emergence.

Due to the increase in studies and technological advances that facilitate the cultivation of beans, and the good consumer market, the use in crop rotation systems that aim to improve the agricultural environment, the grain, which was previously considered subsistence, being cultivated by small for medium producers, it also became interesting for large rural producers. According to Botelho et al. (2018), in addition to being the largest producer, Brazil is the largest consumer of this legume, with an annual production of approximately 2,8 million tons.

Bean cultivation (Phaseolus) is of great importance on the national scene. In the 2017/2018 harvest, more than three million hectares were planted (Conab, 2018). Crop productivity in Brazil averaged 1.095 kg ha^-1, however some regions had an average of 2.455 kg ha^-1 in the 2016/2017 harvest (Conab, 2017). This difference in productivity can be explained by the fact that small producers cultivate the grain for subsistence.

For production to achieve significant results, constant care is necessary from soil preparation to harvest. Soil preparation must be done efficiently to guarantee the best conditions for crop development and establishment. Good soil preparation and good sowing provide the seed with better contact with the soil, consequently, better absorption of water and nutrients, ensuring effective germination and emergence.

In conventional soil preparation, surface layers are disturbed to reduce compaction, incorporation of amendments and fertilizers, increase in pore spaces and, thus, increase permeability and air and water storage (Santiago & Rossetto, 2007). The longitudinal distribution of seeds and the speed of seedling emergence can be influenced according to the soil preparation used.

The different equipment used for periodic soil preparation causes different changes in its physical properties. Citing as an example, an area prepared with a rotary hoe will provide a more homogeneous mixture and a more uniform surface, with smaller aggregates, making it generally suitable for receiving sowing, but operating at a lower depth in the soil, when compared to the action of a disc plough. This, in turn, reaches greater depths, but requires one or two more operations to break up and level the soil surface and adapt it for the sowing operation.

Conventional soil preparation provides several effects for the installation and maintenance of bean crops. That said, a study was conducted in one of the experimental fields at the Federal University of Viçosa, Campus Paranaíba River – MG, which has an average altitude of 1100 meters, with the objective of evaluating the influence of primary soil preparation carried out with a disc plow, rotary hoe, scarifier and intermediate plow harrow on the longitudinal distribution of seeds, emergence speed of seedlings,  productivity and components of bean production. The area was classified as a dystrophic RED – YELLOW Oxisol, clayey texture, flat relief, which has been cultivated with grains since 2014 with the same preparation systems.

In the field

The experimental design was completely randomized (DIC) with four treatments and four replications, with the treatments being periodic primary soil preparation with: disc plow, intermediate harrow, scarifier and rotary hoe. Thus, resulting in a total of 16 experimental units, where each plot consists of an area of ​​100 m² (10 x 10 m), these are separated by carriers, also measuring 100 m², intended for traffic, maneuvers and equipment adjustments.

To carry out soil preparation, the New Holand TL85E tractor was used, operating at 2000 rpm, with reduced third gear and an average speed of 5 km hˉ¹. The same tractor was used in the operations of all equipment. The disc plow used was from the Baldan brand, model AF-3, with 3 discs and a working depth of 0,20 m. The intermediate plow harrow, brand Köhler, model GAC300 with 14 discs and action depth of 0,15 m. The scarifier, Jumbo Matic Hydraulic model, JAN brand, with cutting discs, five parabolic rods and wingless tips, with a working width of 2,0 m working up to 0,2 m deep. The rotary hoe, brand MEC-RUL, model ERP 200 B, with 8 flanges and 48 blades and action depth of 0,10 m. After primary soil preparation carried out with the disc plow, intermediate harrow and scarifier equipment, two harrowings were carried out for declogging and leveling.

Once the soil was prepared, the BRS style bean culture was installed, with a cycle of approximately 100 days. The sowing spacing between rows was 0,5 m, using the Massey Ferguson 4292 tractor, operating in reduced 3rd gear, 1600 rpm and an average speed of 5,0 km h.^-1. The seeder-fertilizer was adjusted to deposit 15 seeds m^-1, at an average depth of three centimeters, estimating a stand of 300.000 seeds ha^-1. Planting fertilization was carried out with the formula 08-30-10, at a dose of 400 kg ha^-1. For top dressing, urea was used at a dose of 400 kg ha.¹ paid in two installments.

To evaluate the longitudinal distribution of seeds, two meters of line in the central row were used as a useful plot, where the distance between seeds was measured. When carrying out the measurement, care was taken not to remove the seeds from the place where they were sown, to avoid changes in the results. The established population was 300.000 seeds ha^-1, with a row spacing of 0,5 m, resulting in 15 seeds m^-1 for all treatments, resulting in a nominal spacing (Xref.) of 66,67 mm. The spacings were classified as acceptable (0,5 Xref.< Xi< 1,5 Xref.), double (≤ 0,5∙Xref.) and faulty (≥1,5∙Xref.).

To determine the number of emerged seedlings, an interval of two meters was used in the central row. According to Carvalho Filho et al. (2006) an emerged seedling was considered to be one that broke through the soil and could be seen with the naked eye, from any angle. The demarcation of two meters in the central row was carried out as follows: starting at the edge of the plot, two meters were measured, a stake was fixed, from that stake another two meters were measured, where a second stake was fixed , so the count of emerged seedlings was done in the interval between cuttings. Therefore, the count was carried out daily until the number of seedlings stabilized for three consecutive days, as proposed by Silva (2002), then it was obtained from the equation (Edmond and Drapala, 1958), the average number of days for seedling emergence.

Where: M - average number of days for corn seedlings to emerge; N1 - number of days elapsed between sowing and the first seedling count; G1 – number of seedlings emerged in the first count; N2 - number of days elapsed between sowing and the second seedling count; G2 - number of seedlings emerged between the first and second counts; Nn - number of days elapsed between sowing and the last seedling count; Gn - number of seedlings emerged between the penultimate and last count. The collected data were tabulated and subjected to analysis of variance and then the Tukey test was applied at 5% probability to compare the means. When necessary, the variables were transformed, but the original averages were used in the table so that the values ​​are consistent with practice.

The different soil preparation systems did not influence the longitudinal distribution of seeds, where the general average for spacing was 58,25% normal, 5,14% double and 36,62% failed (table 1), corroborating what was presented by Mahl et al. (2006).

The evaluation of seed spacing showed high variability, demonstrated by the coefficient of variation. For this type of analysis, it is common to obtain high coefficient of variation values, such as those presented by Kurachi et al. (1989); Cortez et al. (2006); Santos et al. (2011); Melo et al. (2013).

The average number of days for seedling emergence was influenced by the different periodic soil preparations, with the harrow being the one that obtained a statistically greater result compared to the disc plow and rotary hoe (table 1). Silva & Gamero (1993), evaluating the influence of secondary preparation, carried out with the declogging-leveling harrow, before or after primary soil preparation, carried out with the disc plow, plowing harrow and scarifier, observed a lower speed index value of emergence of bean seedlings when harrowing before plowing.

However, Boller and Caldato (2001), evaluating the effect of three soil preparation systems (disc plow + light harrow, scarifier and direct planting) on ​​the development of bean crops, observed that the average number of days for seedling emergence did not was influenced by different soil preparations. Similar results were observed by Carvalho Filho et al. (2006) and Silva (2015), where they evaluated the effect of five soil preparation equipment on soybean development.

It can be seen from the data in table 2 that bean grain productivity was not changed due to periodic soil preparation. Thus, even though the emergence speed was influenced by soil preparation, productivity remained statistically the same between treatments. In this way, the data obtained demonstrate that the producer can choose the preparation that best adapts to his reality, as this will not cause differences in his production.

The final number of plants per hectare, number of pods per plant and number of grains per pod are components of bean crop production. Conventional soil preparation did not influence any of the production components (table 2). Silva (2015) also found no differences in the average number of pods per plant.

Although soil preparation is important to provide the best conditions for the establishment and development of crops, in this work, there was little influence on the productive characteristics of the crop, and thus the producer's profitability. Therefore, according to Silva (2015), one should opt for systems that provide better operational capacity and lower costs in adapting the soil for sowing.

Through the data found in this study, no statistical difference was found in the longitudinal distribution of seeds. The average number of days for seedling emergence was influenced by soil preparation equipment, with the plow harrow having a higher average compared to the disc plow and the rotary hoe. Although there was a statistical difference in the average number of days for seedling emergence, this was not verified for the productivity and production components of the bean crop.

 

Luiz Fernando Costa Ribeiro Silva, Letícia Almeida, Vitor Lavorenti Arthur, Lucas Balbino Fois Lanna, Alberto Carvalho Filho, Renato Adriane Alves Ruas, Federal University of Viçosa – Rio Paranaíba Campus