چكيده لاتين :
Introduction
Tea leaves harvesting practically starts from April to November in two provinces (Guilan & Mazandaran), due to being located in rain fed and mountainous areas. In unirrigated fields during a drought season, the yield quality was reduced at the middle of growth periods (Majd Salimi & Mirlatifi, 2008). Therefore, to avoid the loss, improve the quality and increase yield, tea bushes needed supplemental irrigation during a drought season (Stephens & Carr, 1991a). According to reported research works in different tea cultivating countries, water use efficiency of produced tea was between 1.5-9 kg.ha-1.mm-3 of used water. This variation practically depends on the type of irrigation system, amount of rain and irrigation, clone type, fertilizer amount and type, season, climatic conditions, field management, age of bushes as well as harvesting (Carr, 2010 a,b; Stephens & Carr, 1991 a,b). There is no report to indicate water use efficiency in tea fields in farmers management conditions .The results of some research works on optimal use of water and fertilizer showed that water use efficiency in rain fed (non irrigated) case was between 2.1-6.7 kg.ha-1.mm-1 of used water (rain) and in complete irrigation condition it was between 4.6-8.7 kg.ha-1.mm-1 of used water (rain and irrigation water). According to the results, water use efficiency variation depends on climatic condition (high temperature and air humidity deficit), applied nitrogen fertilizer and interval of irrigation (Majd Salami et al., 2011; Majd Salami, 2012). This investigation was conducted to ascertain yield quality, used water, irrigation use efficiency and water use efficiency in tea fields in the Guilan province and to analyze field management, harvest and effective irrigation variation factors on this index in farmers management conditions.
Material and methods
The rate of water productivity (WP) was assessed in six irrigated tea fields and three rain fed (non irrigated) cases in farmers management method for two years (2009-2010). During the growing season, yield quality of each field in successive harvests, including soil moisture were assessed with the help of gravimetric soil method and water balance equation. Volume of water entered the irrigation system and amount of water reached to surface level were measured. The amount of rainfall was measured using rain gauge installed at the site. The United State Department of Agriculture (USDA) method was used to measure the effective rainfall. During the growing season, soil moisture balance equation and soil moisture monitoring and measurement were conducted in all selected fields, with the help of sampling weights method (average of weight in three depths of root). For selected tea fields in rainfed conditions (WS, CN and EM), production per unit of effective rainfall or water productivity due to effective rainfall (WPp) and gross irrigation water consumption productivity and actual water consumption productivity (evapotranspiration) in irrigated tea fields (WA, WB, CG, CK, EP & ED) were determined. Also, water irrigation productivity (IWP) in irrigated tea fields was calculated.
Result and discussion
The mean quantities of made tea in irrigated and rainfed cases were 2843 and 1095 kg ha-1, respectively. Average of gross irrigation and effective rainfall (WP) and irrigation water productivity (IWP) in the irrigated fields were 4.39 and 4.55 kg. (made tea) ha-1.mm-1 and average of net WP (actual evaportanspiration) and net IWP was 5.18 and 6.61 kg.ha-1.mm-1, respectively. Average WP in rainfed tea fields was 3.4 kg.ha-1 for each mm of effective rainfall. The most effective factors on WP reduction in tea fields were improper harvesting operations (non-standard plucking) and economic problems. Moreover, improper operation and maintenance and old irrigation systems and unprincipled irrigation scheduling in irrigated tea fields were also effective on WP reduction. Comparing the results of this study with other studies in the past showed that implementing the proper methods in irrigation management and appropriate agricultural practices can improve water productivity in tea fields.
References
Carr, M.K.V. 2010a. The role of water in the growth of the tea (Camellia sinensis L.) crop: a synthesis of research in eastern Africa. 1. water relations. Experimental Agriculture 46(3): 327-349.
Carr, M.K.V. 2010b. The role of water in the growth of the tea (Camellia sinensis L.) crop: a synthesis of research in eastern Africa. 2. water productivity. Experimental Agriculture 46 (3): 351-379.
Majd Salimi, K. 2012. Interaction of irrigation levels and amounts of nitrogen fertilizer on yield and quality of tea green leaf. Final Report. Agriculture Research, Education and Extension Organization, Tea Research Institute of Iran 133 pp. (In Persian with English Summary)
Majd Salimi, K., Salvatian, S.B., and Rezaeii, M. 2011. Effects of sprinkler irrigation intervals on yield and water use efficiency of tea fields in Giulan Province, Iran, Journal of Water and Soil 24(6): 1129-1141. (In Persian with English Summary)
Majd Salimi, K., and Mirlatifi, S.M. 2008. Tea (Camellia sinensis L.) yield response to irrigation and nitrogen fertilizer applications, Journal of Science and Technology of Agriculture and Natural Resource, Water and Soil Science 12(44): 39-50. (In Persian with English Summary)
Stephens, W., and Carr, M.K.V. 1991a. Responses of tea (Camellia sinensis) to irrigation and fertilizer. I. Yield. Experimental Agriculture 27: 177-191.
Stephens, W., and Carr, M.K.V. 1991b. Responses of tea (Camellia sinensis) to irrigation and fertilizer. II. Water use. Experimental Agriculture 27: 193-210.
