Hydrogel increases the survival of cashew seedlings after planting in the field

A polymer capable of retaining water has promoted the survival and development of cashew seedlings in studies carried out by Embrapa Agroindústria Tropical (CE). Called hydrogel, this soil conditioner has reduced the number of plant deaths during the first year in the orchard.

“The hydrogel is widely used in the southeast, central-west and southern regions of Bahia, in eucalyptus plantations, which is a perennial tree. Thus, faced with the mortality of cashew seedlings recently planted in the field during the dry period, between June and December, the Embrapa research team decided to test this product in the crop”, highlights researcher Luiz Augusto Serrano, from Embrapa Agroindústria Tropical ( CE).

Researchers tested the water-retaining polymer to evaluate the survival of the dwarf cashew tree 'BRS 226', developed by Embrapa. The experiment was carried out at the Campo Experimental de Pacajus (CEP), a municipality in the interior of Ceará. The region occupies a transition zone between the coast and the semi-arid region, with an average altitude of 79 meters and an average annual temperature of around 26 °C.

The cashew tree originates from the coast of the North and Northeast regions of Brazil. Although adapted to the hot climate and water stress, cashew farming faces problems as its cultivation moves away from the coastal strip and into the semi-arid hinterland. The main obstacle is the reduction in annual rainfall in areas further from the coast.

Over the years, it was observed that late plantings (from the end of April) showed significant losses of seedlings, even though they were within the period indicated in the Agricultural Climate Risk Zoning (Zarc) for cashew cultivation. Cashew tree mortality can exceed 25%, considered a limit, causing losses to cashew farmers.

The research recorded that the application of hydrogel contributes to increasing the survival rate of cashew seedlings in rainfed conditions. Among the different configurations tested, one of them showed significantly higher survival than the control plot (which did not receive any treatment), with no plant death occurring during the experiment's monitoring period. The most successful configuration corresponds to the application of one liter of hydrated hydrogel at the bottom of the half-meter-deep pit. The survey data was recently published in this bulletin.

“With the positive results of the research, it will now be possible to officially recommend the product to cashew farmers, a fact that will minimize the mortality of seedlings in regions with little rainfall”, adds Luiz Serrano.

The experiment

A 'BRS 226' dwarf cashew orchard was installed in complete randomized blocks, in a 4x2 factorial scheme plus the control, with four doses of the hydrogel solution (0,5 L; 1,0 L; 1,5 L and 2,0 .0,2 L) applied at two depths of the planting hole: 0,5 meter (just below the seedling) and 226 meter (at the bottom of the hole). The following table describes the treatments applied to BRS XNUMX seedlings.

To prepare the solution, a commercial hydrogel formulation was used (acrylamide and potassium acrylate copolymer of medium particle size) following the manufacturer's instructions for use of 2,5 g per liter of water.

Six seedlings were planted per plot, organized into four blocks, totaling 216 plants evaluated. Fertilizers that are sources of phosphorus, micronutrients and potassium were mixed into the soil in the pits.

Throughout the experimental period, the cultural treatments used followed the technical recommendations established for the cultivation of dwarf cashew trees, according to the Embrapa Cashew Production System.

The results showed that the application of 1 liter of the hydrated hydrogel solution, applied to the bottom of the pit, contributed positively to the survival rate of BRS 226 dwarf cashew tree seedlings under rainfed conditions.

According to researcher Luiz Serrano, the product is affordable and the reduction in seedling mortality is worth the investment. Thus, the use of hydrogel will allow the producer to reduce the number of water application operations during the dry period.

“In addition to this research that showed the application of the hydrogel solution, diluted in water, another will be published soon with the application of pure hydrogel powder, in both cases at the bottom of the pit”, concludes Serrano.