Crescimento e desenvolvimento do pinhão-manso irrigado com águas residuária e salinizada - segundo ciclo de produção.

Abstract

ysic nut {Jatropha curcas L.) it is an oleaginous plant, currently in domestication process and in researched for biodiesel production. Between May 2008 and January 2009, two experiments were installed and carried out in a greenhouse, at the Natural Resources and Technology Center at the Federal University of Campina Grande - PB with the objective of studying the effects of the irrigation with saline water and sewage wastewater on the growth and development of Jatropha plants at second cycle of production after being pruning, beyond to evaluation of its impacts on soil and plant nutritional status in the end of the research. The plants were grown in drainage lysimeters (200 L) containing 230 kg of non-saline and nonsodic soil. In Experiment I (use of wastewater). the statistical design in randomized blocks was adopted, in 5x2 +1 factorial scheme with four replications, five 5 leveis of irrigation (Li) were studied, based on evapotranspiration replacement of the plant (ETc): Li (Lii = 25; LÍ2 = 50; Li3 = 75, = LÍ4 = 100 and Li5 = 125% ETc), 2 pruning heights ('pruning low' - plants pruned at the height of 40 cm, and 'high pruning' - plants pruned at 80 cm) and a control treatment (plants irrigated with water from public supply without hidric restriction). In Experiment II (use of saline water). treatments consisted of five leveis of electrical conductivity of the irrigation water - ECw (0.6; 1.2; 1.8; 2.4 and 3.0 dS m"1, at 25 °C), also arranged in the experimental design of randomized block with four replications. Ali the plants, in beginning, were pruned at 80 cm height. In both experiments, the experimental unit consisted of two lysimeters, each containing one plant. The plants were watered at 3 day intervals. Experiment I (use of wastewater): water stress affected the growth of physic nut plants, and the leaf area was much sensitive. Low leveis of water replacement in the soil, as 25% ETc, causes delay of 65 days in the beginning of flowering. Fruit production was more sensitive than growth. Plants were more productive when irrigated with 125% of evapotranspiration, producing more than 400 g of seeds, on average, with oil content of 36.24%. The application of sewage wastewater improved the soil chemical properties. At 240 days after pruning, the initial concentrations of nutrients were increased by improving the sum of bases-S, cation exchange capacity-CEC and base saturation and, pH increased linearly with the rate of replacement leveis. Sodium was the most accumulated in the leaves (11,160 mg kg" '). Plants subjected to high pruning (80 cm), fructified more and earlier and more productive. n general, plants irrigated with wastewater with replacement leveis more than 50% ETc had growth equivalent or significantly higher than those in control treatment, besides being earlier. Regarding the control, soil fertility was improved with the application of wastewater, with pronounced effect on the P, Ca, sum of bases (S), base saturation and cation exchange capacity - CEC, reflecting on N-leaf, P-leaf and Ca-leaf, but without improving the quality of seed oil. Experiment II (use of saline water): initially, the salinity of irrigation water stimulated the emergence of shoots, the number of leaves and the leaf area at 30 days after pruning, and their indexes increased with the increasing of ECw, leading to higher evapotranspiration. After 90 days of pruning, evapotranspiration rate was reduced linearly with increasing ECw. At 240 days after pruning, the plant height, stem diameter, leaf number and leaf area of physic nut were affected linearly with decreases of 2.52, 5.05, 15.45 and 12.17%, respectively, per unit of ECw increase. The beginning of flowering (105 days), fructification (147 days) and maturation (188 days) were affected, linearly, by salinity with delay of almost two weeks for each ECw increase (dS m"1). The fruits ripened between 9 and 10 days, regardless of salinity levei. The yield components were severely affected with reductions of up to 90% in plants irrigated with ECw equal to 3.00 dS m"1. Plants irrigated with water of 3.00 dS m"1 until 240 days after pruning produced one or two fruit bunches. Individual weights of seed and fruit were significantly affected with reduction of 20.60% and 27.92% for each increase of 1 dS m"1 in irrigation water. Soluble ions were accumulated in the soil solution, in the following sequence of concentration: Cl" > Na+ > HCO"3 > Ca++ = Mg++ > K+ (29.05 > 17.39 > 10.00 > 9.40 = 9.22 > 0.36 mmolc L"1), characterize the soil as nonsaline. Cálcium, sulfur, zinc and copper leveis were lower than the appropriate leveis reported in literature. Sodium was the most accumulated element in the leaf (15,477 mg kg"1). The oil content of physic nut fruits was compromised when the plants were irrigated with saline water up to 0.60 dS m"1; plants irrigated with water of 3.0 dS m"1 (22.5% oil), compared to 0.60 dS m"1 (32.03% oil) had oil content reduced by about 30.55%.