Respostas ecofisiológicas e desempenho agronômico do amendoim cv. BR1 submetido a diferentes lâminas e intervalos de irrigação.

Abstract

This research was conducted taking into consideration, the potential importance of the groundnut crop {Arachis hypogaea L.) for the Northeast Brazil, where the consumption is ten times more than the production, and the lack of agronomic information about the irrigation requirements of this crop as well as the growth and development of the plant. The main objective was to evaluate the ecophysiological responses and the agronomic performance of the irrigated groundnut crop, cultivar BR1, in the municipality of Rodelas - BA Growth, morphology, assimilates partitioning, stomatal resistance, photosinthetically active radiation, transpiration, and crop as a function of the amount of irrigated water and the frequency of irrigation were analyzed. Three different levels of irrigation (300 mm, 500 mm and 700 mm) and three different frequencies of irrigation (2 days, 4 days and 6 days) for each level of irrigation (which resulted in 9 different treatments) were applied under the field conditions using the randomized block design with a 3 x 3 factorial analysis scheme. In general, the growth rates of the crop decreased with the decrease of the amount of irrigated water and increase of the irrigation interval. The highest value of 16.11 g.m~2.day~' of the crop growth rate (CGR) was observed in the case of the treatment of 700 mm/ 4 days and the lowest CGR was observed in the case fo the treatment of 300 mm/ 6 days. Net assimilation rate (NAR) and the relative growth rate (RGR) were declined with ontogenesis and also with the reduction of the available water. The leaf area ratio (LAR) was not affected by the treatments imposed. One day after the irrigation (60 DAS), the stomatal resistance was minimum at 10:30 A M and at 12:30 P.M., respectively, for the treatments of 300mm/ 4 days and 700 mm/ 4 days. The stomatal resistance, under well irrigated conditions, presented a hyperbolic relation with the incident photon flux density. The leaves of the groundnut crop present stomatal dimorphism. The groundnut crop should be irrigated when the resistance reaches a value of about 4 to 5 s.m"1. The production function obtained for the groundnut seeds was: Ys e e d =487,63+l,334*L+168,28*T-0,Q0032*L2- 55,31*T2+0,3333*L*T; and the same for groundnut in shell: Y A e H = 603,08 + 3,625*L + 100,37*T - 0,0023 *L2 - 57,60*T2 + 0,454*L*T. The best yields were obtained when the irrigations were applied at higher frequency (2 or 4 days) which can be explained by the low water retention capacity of the soil. For the prevailing conditions in Rodelas - BA, the treatment with 700 mm/ 4 days is indicated for growing the groundnut crop, cultivar BR1