Productive performance of Cynodon spp. cv. Tifton 85 submitted to different irrigation managements

• Grant number: 13/17572-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2013
• End date: July 31, 2014
• Field of knowledge: Agronomical Sciences - Agricultural Engineering - Soil and Water Engineering
• Principal Investigator: Fernando Campos Mendonca
• Grantee: Caroline Salles de Miranda Motta
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

The use of pasture as the basis for dairy or beef cattle feeding is one of the ways to reduce production costs and make the activity more competitive. In order to achieve maximum forage productivity, it is essential to have ideal conditions for photosynthesis, such as good availability of light, nutrients, and water. One of the options for increasing pasture productivity is irrigation, however, there is little acknowledgment about the relationship between soil water availability and forage productivity. It is necessary to define the optimal interval between irrigations, providing adequate water availability to the plants, as they can perform their productive and reproductive functions. This work aims to study the productive performance of Cynodon spp. cv. Tifton-85 under different irrigation frequencies, defined from different soil water depletion factors (p), and to determine the soil water depletion factor that optimizes the forage plant production. The research will be carried out in a greenhouse located in the experimental area of the Biosystems Engineering Department, ESALQ/USP), Piracicaba, SP, under the statistical design of random blocks, in a 5 x 7 factorial scheme with five treatments and seven measures (cuts of the shoot and root samples), and four replications (140 experimental units). We will evaluate the effects of five levels of water depletion in the soil (P1 = 0 to 0.05, P2 = 0.20, P3 = 0.40, P4 = 0.60, P5 = 0.80), which define the irrigation time, related to the soil water percentage, respectively, in 95%-100% (control), 80%, 60%, 40% and 20% of the available soil water. The experimental units will consist of pots with a volume of 8.5 liters, filled with the soil of the experimental area, corrected in their fertility levels, in which will be transplanted seedlings of Tifton 85 grass. The seedlings will be grown until they reach the height of 20-25 cm, and then it will be done the leveling cut and will be started the treatments. The sampling for destructive and non-destructive evaluations will be started after the establishment period and the leveling cut. The samples for destructive evaluation (removal of potted plants) will be made every 21 days, sampling the plants of four experimental units per treatment (20 units/ sample). The plants of the remaining experimental units will be cut at a height of 5 cm from the soil surface, in order to simulate the cycles in a rotational grazing system. The samples for nondestructive evaluation will be made every 7 days, measuring: (a)plant height, (b) stem height, (c) height of the ligule of the previous leaf to the apex, (d) stem diameter, (e) number of tillers, (f) number of expanded leaves and (g) number of senescent leaves. In all the cuts, the plants will be separated into blades and sheaths + culms. The roots will be separated and washed. Both the plant parts, aerial parts, and roots, will be placed in a forced-air oven, for drying at 65 degrees Celsius until they reach a constant weight. After drying the plant material, it will be determined the dry matter production of the leaf blade (MSLF), stems and sheaths (MSCB), and roots (MSR). The dry matter of the plant aerial part (MSPA) will be the sum of the weights of its components. The results will be submitted to the analysis of variance, in order to detect significant differences between treatments. If so, the averages will be compared by using the Tukey test at probabilities of 1% and 5%. (AU)