Crop water requirement calculations of Longan (Dimorcapus longan L.) in Nawungan Orchard, Selopamioro Village, Imogiri Sub-District, Bantul, D.I. Yogyakarta

This research was aimed to measure actual evapotranspiration, to determine of water requirement and crop coefficient (Kc) of longan (Dimorcapus longan Lour.) was cultivated in Longan Nawungan orchard, Selopamioro Village, Imogiri Sub-district. Plot scale of water balance was applied to determine ETa, with input components were rainfall and irrigation, while output were ETa, water storage (ΔSM), and surface runoff (SRO). Components of runoff was measured using tank and the moisture content was measured using gravimetry method. Automatic weather station was installed in Nawungan orchard to record rainfall, wind speed, air humidity, and intensity of solar radiation. Later, the climatic data were used to calculate the reference evapotranspiration (ETo) using Penman-Monteith method. Due to agroforestry and mix cropping system, longan trees were cultivated among seasonal crops and other trees, then the dual crop coefficient (Kc) was preffered. During February-Maret 2019, the value of rainfall and surface runoff were 640 mm during observation period and 0,08 mm, respectively. The reference evapotranspiration (ETo) and actual evapotranspiration (ETa) were 5,76 mm/day and 7,90 mm/day, respectively. The crop coefficient of longan in the site study area was 0,30.


Introduction
Dimocarpus longan Lour. known locally Longan is one of the crops with good prospects, can be seen from the needs of the fruit in Indonesia reached 29 thousand tons in 2012 [1]. Longan (Dimocarpus longan L.) is not native to Indonesia, but originated from China, so the plants belonging subtropics [2]. Longan in Indonesia has been quite a long time and there are several varieties cultivated among others: local longan, Pingpong, and Diamond River of Vietnam, Itoh from Thailand and Malaysia. In Indonesia, Longan is commonly found in Java in several districts, including Ambarawa, Magelang, Temanggung, Wonogiri in Central Java, and Tumpang in East Java [3]. Longan is able to bind water so well that crop water needs are met. Meeting the needs of the crop water use in precision farming system. Precision agriculture is an integrated farming system based on information and production, to increase efficiency, productivity and profitability of agricultural production from upstream to downstream sustainable, sitespecific as well as minimizes the undesirable effects on the environment [4]. Precision approach to water supply timely and volume on horticultural crops is done taking into account the specific conditions of the land, soil moisture, soil type, and the planting period [5]. Irrigation is the provision and regulation of water to support agriculture that kind include surface irrigation, underground irrigation and irrigation pumps. The purpose irrigation drain water is regularly needed by plants when the soil moisture supply is not sufficient to support the growth of plants, so the plants can grow optimally. Irrigation scheduling important role in water management objectives effectively and efficiently in the process of agricultural production. Irrigation is one factor affecting the crop water needs. In addition, the climatic conditions and crop coefficient be other factors in determining crop water requirement [6].
Crop water requirement is the amount of water that plants need to form a network of plants, evaporated, percolation and soil tillage. Real water needs for agriculture business area includes evapotranspiration (ET), amount of water required for operation specifically as clearing land and water replacement, and loss during use [7]. With the value of evapotranspiration can be seen the value of crop coefficient (Kc), Kc is generally used to estimate the value of the ETc in a way be used as a multiplier of the value of potential evapotranspiration (ETo). In Longan crop, crop coefficient (Kc) there was not a valid information especially in Indonesia. In the Food and Agriculture Organization (FAO) has information related crop coefficient (Kc) of each species of plant in the world. Longan is not yet registered for the plant crop coefficient (Kc) for both tropical and subtropical countries. So from that need for research in finding a crop coefficient (Kc) Longan plant.

Methodology
The study was conducted in the area of Nawungan Orchard, Selopamioro Village, Imogiri, Bantul, which began Novenber 2018 to March 2019. This study consisted of three phases, preparation, field data collection, and data processing. The determination of the parameters in this study using the basic guidelines of the book Food and Agriculture Organization (FAO) 56 and principles of the water balance. Methods of data collection, observation and identification of agro-climatic water balance, laboratory testing and documentation. Rainfall data from the last 10 available from the Institute for Water Resources Management (BPSDA) DIY, Barongan climate station, which is the closest climate station of the village Selopamioro. Garden microclimate data were collected by Automatic Weather Stations (AWS), levels of soil moisture was measured by taking soil samples in undisturbed around the plant roots longan using ring sampler, percolation was measured by using a double ring infiltrometer, and Surface Runoff (SRO) is measured by isolating the land, then placed the container in the form of a series of pipes and bucket. Data processing method using descriptive analysis of qualitative and quantitative through,evapotranspiration by the method of Penman-Monteith and water balance, Unit Land (SUL) obtained by overlaying map includes a map of the study area, a contour map , map of soil type and land use maps. Kc value calculated longan longan dual between plants and peanut planting in the garden because the system uses the technique of intercropping.

Research area
Selopamioro village located in Imogiri, Bantul, Yogyakarta (DIY). Selopamioro village has an area of 22.75 km2 and is bordered by Sriharjo; Imogiri in the north, bordering Gunung Kidul regency in the south, border with the Village Mangunan; Dlingo sub-district in the east, and border with the Village Seloharjo; Pundong west. Geographically,The village is located at the position Selopamioro -7.951495 ° S / 110.392040 ° E [8]. Location of the study presented in Figure 1. Longan orchards have a mean minimum temperature of 23 o C, mean maximum air temperature of 32 o C, the average wind speed 0.25 m.s -1 , and an average of 90% RH. These conditions suit the requirements grow crops according to FAO, which is the optimum temperature 25-32 o C, maximum wind speed of 0.85 m/s and a minimum of 40% RH. Plant Longan can be planted in areas with an annual rainfall between 1,000-3,000 mm by the number of dry months (<60 mm) as much as 3-6 months [3] so that the precipitation is in the Nawungan Orchard suitable for plant growth Longan. Longan block in the Orchard Nawungan have an average height of each tree ± 2-4 meters with a slope of 15-40°and has an area of 4,789 m 2 . Longan population which can be grown in the Orchard Nawungan as many as 52 trees. Based on the survey, Longan plants in the Orchard Nawungan grow well. At Longan block planted crops also a distraction, such as peanuts, peppers, and paddy. Planting of distraction depends farmers land owners. At the time of data collection, land planted with peanuts begin to grow (Figure 2). Land planted with red chili toward the harvest period ( Figure 3) while land planted to paddy is at mid-season phase ( Figure 4).  Longan in the Nawungan Orchard grown on soil type Mediterranean or Regosol. Mediterranean soil is limestone soil type of the result of weathering limestone (limestone). Mediterranean soil color tends to reddish brown and less fertile, suitable for planting crops, teak, tobacco, and cashew nuts. This land is spread on subhumid region, karst topography and volcanic slopes with an altitude below 400 m, which is in Nusa Tenggara, Maluku, and Central Java [9]. These soils are not in accordance with the plant Longan, Longan can cropped such as soil type Andosol, Vertisol, Lateral, or laterit [3]. The soil texture in the form of clay blocks classified Longan (clay) are presented in Table 1. Based on Table 1, the highest percentage of clay fraction and sand fraction is lowest. The land of the Mediterranean / Alfisol textured clay or clay loam, with some of the physical characteristics, namely the depth of solum moderate to shallow (90-200 cm), the structure of blocky angular, and has a neutral pH to slightly alkaline [10]. Identification of the soil texture on a Longan block accordance with the general nature of the land of the Mediterranean.  Figure  5, it is known that the greater the value of surface rainfall runoff that occur will be greater. Rainfall has an influence on the size of the surface flow. When rainfall is <5 mm there will be no surface runoff.

Water storage.
Water storage in soil occurs due to the influence of the amount of rainfall. Based on Figure 6, an increase in moisture content due to the amount of rainfall that occurred. It also happens to surface runoff despite occur very little due to the soil types ahan Mediterranean / Alfisol. The land of the Mediterranean / Alfisol textured clay (clay) or clay dust (clay loam), with some of the physical characteristics, namely the depth of solum moderate to shallow (90-200 cm), the structure of blocky angular, and has a neutral pH to slightly alkaline [10].With clay texture easy absorb water but when large rain occurs, the land will become saturated. Saturated soil can not store water in the soil resulting in decreased when the soil is no longer able to accommodate the water contained in the soil and the water becomes runoff.   In addition, the water storage in the soil is influenced by the thickness of rainfall there suface percolation and runoff. In this study, percolation is used at 2.5 mm / day as a reference.