SILVA, L. C.; SILVA, Luiz Carlos.
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
