Biomass , Protein Content and Cell Damage in Tanzania Grass Irrigated With Saline Water

The scarcity of good water quality in semiarid region, combined with the high cost of pumping, has been the main limiting factor for increasing the irrigated area. The use of saline water for irrigation is a very common in semiarid zones, which can result in the soil salinization if irrigation management is not appropriated. To evaluate the biomass production, biochemical components and water consumption of Tanzania grass (Panicum maximum) irrigated with water salinity (1.5, 3.0, 4.5 and 6.0 dS m) an experiment in greenhouse was carried out in the Universidade Federal Rural do Semi-Árido, Mossoró, Rio Grande do Norte State, Brazil. The variables dry matter, crude protein, ashes, cellular damage on leaves and consume water in the first and second cut of the grass were analyzed under completely randomized design with five treatments and six replications. Salinity water up to 6.0 dS m can be used for irrigation of Tanzania grass plants, with small yield losses. Increased salinity reduces water consumption and increases the water use efficiency of Tanzania grass. Tanzania grass plants have increased protein content when subjected to saline stress, which is a mechanism of action to osmotic adjustment and allows the reduction of plant leaf damage in the second cycle.


Introduction
In the agricultural development pole of Rio Grande do Norte, part of the water used for irrigation comes from deep wells, which despite the good quality, presents a high cost to obtaining, making it unviable to use in agriculture.However, there are also open wells in the region of the Jandaíra limestone that, although even having a low cost of obtaining, has a high concentration of salts.In the irrigated crops of this region, due to the low cost it has been common the replacement of non-saline water by brackish water of the shallow wells.The waters of the limestone aquifer present relatively high concentrations of salts, being able to be superior to 3.0 dS m -1 (Sousa et al., 2009), being indispensable investigations on the rational use of these waters, since their inadequate use can salinize the soils (Porto Filho et al., 2011), aggravating the problems of desertification.
Since salinity of irrigation water restricts the production of certain plants, salinity is considered as one of the most important factors of irrigation water (Kim et al., 2016).The effects of salinity on plants can be caused by the difficulties of water absorption, specific ion toxicity and salt interference in the physiological processes (indirect effects), reducing the growth of sensitive plants (De Pascale et al., 2013).However, the effect of salinity depends on several factors, standing out the plant species, the cultivar and the saline composition of the environment; Besides, plant tolerance to salinity is influenced by the stage of growth, time and duration of plant exposure to the salts, environmental condition, substrate type and production system (Cosme et al., 2011;Dias et al., 2011).salinity.Forage plants are considered salinity tolerant and can be used as an alternative to exploit the brackish water of the limestone aquifer, although they suffer reductions in their growth, production and quality of the product when exposed to saline stress conditions (Maia et al., 2015).
Investigations related to tolerance to salinity of crops, despite the great interest involved, are scarce; However, for a rational irrigation management strategy, it is necessary to know the effects of irrigation water salts on the soil and the plant at different stages of development (Melo et al., 2011).These data allow to establish criteria of greater exposure of the plant to the adverse environment and to the need for a good cultural conduction, rationally orienting the irrigation.
In view of the above, it is therefore necessary to conduct research aimed at knowing the production potential of the Tanzania grass irrigated with brackish water, making possible its exploitation in small springs of the Northeast of Brazil.The objective of this work was to evaluate the biomass production, biochemical components and the water consumption of the Tanzania grass under the effect of different levels of salinity of irrigation water.

Material and Methods
The experiment was carried out in a protected chapel type environment with 3, 12 and 16 m height, length and width, respectively, covered with low density polyethylene film with anti-ultra violet additive and thickness of 150 microns, protected on the sides with black mesh 50%, belonging to the Departmento de Ciências Ambientais e Tecnológicas (DCAT), of Universidade Federal Rural do Semi-Árido (UFERSA), in Mossoró, RN, situated 5°11′ S, 37°20′ W and 18 masl.Each experimental plot consisted of a plastic vase with a capacity of 12 L.The vases had their bases drilled with a 10 mm drill, and 10 perforations were made in the perimeter of the lower base.Subsequently they were filled with a 0.02 m gravel layer, covered with geotextile blanket and soil material from Red-Yellow Latosol from the Campus of UFERSA, resulting in a layer of 0.30 m.The soil was sifted, air-dried before being filled into the vases.The vases were placed on wooden benches suspended 0.80 m high, 1.50 m wide, 3.00 m length, located inside the protected environment.
For the establishment of the experiment, a completely randomized design was used, with five treatments and six replications, totaling 30 plots.The treatments consisted of the application of different levels of salinity of irrigation water, represented by the electrical conductivity (EC), being: S 1 = 1.5; S 2 = 3.0; S 3 = 4.5 and S 4 = 6.0 dS m -1 .Water with electrical conductivity (CE w ) of 4.5 dS m -1 was obtained from a deep well, the other levels were obtained by diluting the water 4.5 dS m -1 with local water supply (0.5 dS m -1 ), or by the addition of NaCl, calibrated by a benchtop conductivity meter with automatic compensation for the temperature of 25 ºC.The planting was done by hauling, and when the seedlings reached 5 cm in height a thinning was done leaving 15 plants per vase.The fertilization of the soil of the experimental units was done according to the chemical analysis of the soil material (Table 1), being applied 75, 50 and 40 mg dcm -3 of phosphorus, nitrogen and potassium, respectively, being applied via water of irrigation in six events.Triple superphosphate was used as the source of P, urea as the source of N and potassium chloride as the source of K.The irrigation management was carried out based on soil moisture data, obtained from tensiometers installed at 0.20 m depth and a soil water retention characteristic curve determined in the field.A two-day fixed irrigation shift was established, and irrigation depth was determined by tensiometry, with a tensiometer installed at 0.20 m depth.The applied water volume was calculated from the water retention characteristic curve in the soil and the averages of the tensiometric readings, for each level of salinity.
In order to monitor the microclimate inside the protected environment, five non-aspirated copper psychrometers were installed to read the actual air temperature and relative humidity, recording the averages every thirty minutes and daily averages throughout the environment, that is, temperature in dry bulb and temperature in a moistened cotton gauze, all in the same position in each bench, aiming to measure possible variations in temperature and relative humidity in the plots throughout the day.
The evaluation of the production and biometry of the plants was performed in two consecutive cuts with intervals of 30 days, corresponding to 60 days of accumulated exposure to the brackish waters.The dry matter, crude prot described different tr Using the Tanzania g The evalua in time, u means of a

Results
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