Agroclimate zone analysis for the suitability of rice plantation in Donggala District

As one of the supporting districts for regional food security, the productivity of food crops in Donggala Regency needs to be continuously improved. Climate type information is closely related to business development in agriculture, especially rice plants. This study aims to determine the type and distribution of agro-climatic zones for rice land suitability in Donggala Regency. This study uses the climate classification method according to Oldeman by calculating the number of wet months and dry months for one year which is then mapped using the Inverse Distance Weighted (IDW) method. The data used in this study are rainfall data for 10 years (2011-2020) from 15 points of BMKG rain observation posts as well as the Planting Calendar for rice plants from the Ministry of Agriculture. The results showed that Donggala Regency has 3 Oldeman climate types, namely type A in Rio Pakava District with the suitability of continuous rice cultivation but low production, B in Banawa Selatan and Sojol Districts with the suitability of continuous rice planting with high production when harvested during drought season. Type E in the Districts of Central Banawa, Banawa, Tanantovea, Labuan, Sindue, Sindue Tobata, Sindue Tombusabora, Balaesang, Balaesang Tanjung, North Sojol and Dampelas which is too dry, so that only one planting period of crops is possible. In areas with climate type E it is recommended to optimize irrigation to meet the water needs of rice plants. The agro-climate zone map made using the IDW interpolation method can describe the distribution of climate types as a whole, especially in areas where there are no rain gauge posts such as in Pinembani District.


Introduction
The rice plant is a very important cultivated plant for mankind because more than half of the world's population depends on this plant as a source of food.Almost the entire population of Indonesia fulfills their food needs from rice plants.Thus, rice plants are plants that have important spiritual, cultural, economic and political values for the Indonesian people because of the livelihoods of many people [1].The development of land-based lowland rice requires an analysis of land suitability and land availability in formulating strategic policies and programs to support increased rice production and productivity [2] [3].
Business development in the agricultural sector is closely related to climate types, especially in the development of various types of plant commodities in various regions, because the success of plants to grow and develop is largely determined by the carrying capacity of environmental elements, while the climatic elements on the earth's surface vary greatly.Therefore, knowing the type of climate is very necessary in preparing a solid business plan [4].Regional agro-climatic information such as trends in rainfall changes and climate types is important information that can assist all parties in making policies related to agricultural development [5].The use of the latest climate data in planning and implementing various development activities including agriculture will describe a more representative climate, so that it can be used as a more objective reference such as for regional development in general including agricultural development [6] [7] In the climate classification for rice plants generally use the Oldeman climate classification.The Oldeman climate classification is a climate classification used for food or agricultural crops in Indonesia.The basis used is that there are successive periods of wet months and successive periods of dry months as well.According to [8], Oldeman's climate classification is intended to assist the agricultural sector in determining the planting season in the Indonesian archipelago which has a significant diversity of rain patterns.
Geographic Information System (GIS) is a special information system that manages data that has spatial information (spatial reference).The definition of geographic information is information about a place or location, where an object is located on the surface of the earth and information about the object where the geographic location is to be analyzed in making decisions.Mostly to process data in the form of GIS data, many still use desktop applications or can only be run on one computer, eventhough the more advanced developments require humans to produce information more easily [9].
With advances in technology, the process of identifying regional climates has been integrated with a geographic information system (GIS) so that climate zone data can be displayed in spatial form in the form of zones of regional climate types.This was done to facilitate reading and interpretation of the data [10].One of the techniques used in GIS application for climate zones is the Inverse Distance Weighted (IDW) method.According to the National Center for Geographic Information and Analysis [11], the IDW method is a simple deterministic interpolation method by considering the values at the surrounding points.
The purpose of this study was to determine the agro-climatic classification according to Oldeman for land suitability for rice in Donggala Regency and to determine the distribution of agro-climatic zones according to Oldeman using the Inverse Distance Weighted (IDW) method.

Types of research
This type of research used is quantitative research.Where the rainfall data for Donggala Regency collected are processed in a structured manner to produce agro-climatic zoning according to Oldeman which is then mapped so that it is easy to understand as a whole.

Place and time of research
This research was carried out at the Mutiara Sis Al Jufri Meteorological Station, Palu, which has complete equipment to process rainfall data for Donggala Regency.While the time to carry out this research is from January to April 2021.

Data source
The data used in this study is secondary data in the form of rainfall for each sub-district and planting calendar data (Katam) to determine the initial rice planting schedule in Donggala Regency.Rainfall data in the form of average monthly rainfall for 10 years (2011-2020) and Katam data in the form of the beginning of the rice planting season consisting of 3 planting periods (MT) each year.Rainfall data can be obtained and used by students by attaching a Research Proposal that has been approved by Tadulako University.Meanwhile, planting calendar data (Katam) were obtained from the Agricultural Research and Development website.

Data analysis
This research includes the calculation of the climate classification according to Oldeman which is then mapped to determine the suitability of rice planting land.There are two data processing software used, namely: Microsoft Excel is used to facilitate the processing of rainfall data and classification of Oldeman climate types as well as the creation of rainfall time series graphs at each rain gauge post.And ArcGis 10.1 is used for Inverse Distance Weighted (IDW) interpolation analysis which will produce an interactive map of agro-climatic zones.

Oldeman climate type determination
Oldeman climate type determination to determine the Oldeman climate type in Donggala Regency, it is necessary to go through the stages in order to get the desired results.The steps taken are: The collected daily rainfall data from the rain post for at least 10 years is processed into monthly average rainfall data and entered into a table to facilitate further data processing.In Figure 1 the number of rain gauge posts shown is only 15 out of the 21 previously planned rain gauge post points.This is because there are 6 rain measuring posts that cannot be used because the recorded rainfall data is not sufficient for a 10-year timeframe.The rain gauge posts that cannot be used are the Kabonga Besar, Lero, Simou, Surumana and Tanamea rain posts.

4
Basd on data from the 15 BMKG rain measuring posts in Donggala Regency.Some rain posts have more dry months (<100 mm) than wet months (>200 mm) and there are even rain posts that don't have a wet month at all.

Determination of climate type.
Graph of data series average monthly rainfall from Lalundu rain post, Rio Pakava District, Donggala Regency.The Oldeman climate type for the Lalundu rain post is A1 climate type with more than 9 wet months.Graph of data series average monthly rainfall from the Watatu rain post, South Banawa District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and December, so the type of rain at the Watatu rain post is equatorial.The Oldeman climate type for the Watatu rain post is a B1 climate type with 7 wet months.Figure 2 of the average monthly rainfall data series from the Mount Bale rain post, Banawa District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and December, so the type of rain at Mount Bale rain post is equatorial.The Oldeman climate type for Mount Bale rain post is E1 climate type with a wet month of less than 3 months and a dry month of less than 2 months.
Figure 2 of data series average monthly rainfall from the Nupabomba rain post, Tanantovea District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and September, so the type of rain in the Nupabomba rain post is equatorial.The Oldeman climate type for the Nupabomba rain post is E4 climate type with a wet month of less than 3 months and a dry month of more than 6 months.
Figure 2 of data series average monthly rainfall from the Labuan Salumbone rain post, Labuan District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and December, so the type of rain in the Labuan Salumbone rain post is equatorial.The Oldeman climate type for the Labuan salumbone rain post is E2 climate type with less than 3 wet months and 3 dry months.and January, so the type of rain in the Sindue rain post is equatorial.The Oldeman climate type for the Sindue rain post is the E1 climate type with less than 3 wet months and less than 2 dry months.Figure 2 of the average monthly rainfall data series from the Tibo rain post, Sindue Tombusabora District, Donggala.The average annual rainfall in the region varies, with two rain peaks, namely March and October, so the type of rain at the Tibo rain post is equatorial.The Oldeman climate type for the Tibo rain post is the E1 climate type with a wet month of less than 3 months and a dry month of less than 2 months.
Figure 2 of the average monthly rainfall data series from the Sindue Tobata rain post, Sindue Tobata District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and January, so the type of rain in the Sindue Tobata rain post is equatorial.The Oldeman climate type for the Sindue Tobata rain post is E1 climate type with less than 3 wet months and less than 2 dry months.
Figure 2 of data series average monthly rainfall from the Lompio rain post, Sirenja District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and so the type of rain in the Lompio rain post is equatorial.The Oldeman climate type for the Lompio rain post is the E1 climate type with less than 3 wet months and less than 2 dry months.
Figure 2 of data series average monthly rainfall from the Kamonji rain post, Balaesang Tanjung District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June and December, so the type of rain in the Kamonji rain post is equatorial.The Oldeman climate type for the Kamonji rain post is E2 climate type with less than 3 wet months and 4 dry months.
Figure 2 of data series average monthly rainfall from the Balaesang rain post, Balaesang District, Donggala Regency.The average annual rainfall in the area varies, with two peaks of rain, namely June and January, so the type of rain at the Balaesang rain post is equatorial.The Oldeman climate type for the Balaesang rain post is the E1 climate type with less than 3 wet months and less than 2 dry months.
Figure 2 of data series average monthly rainfall from the Karya Mukti rain post, Damsol District, Donggala Regency.The average annual rainfall in the area varies, with two peaks of rain, namely May and January, so the type of rain in the Karya Mukti rain post is equatorial.The Oldeman climate type for Karya Mukti's rainy post is E1 climate type with less than 3 wet months and less than 2 dry months.
Figure 2 of the average monthly rainfall data series from the Siboang rain post, Sojol District, Donggala Regency.The average annual rainfall in the area varies, with two peaks of rain, namely June and December, so the type of rain at the Siboang rain post is equatorial.The Oldeman climate type for the Siboang rain post is climate type B1 with a total of 7 wet months and less than 2 dry months.
Figure 2 of data series average monthly rainfall from the Ogoamas rain post, North Sojol District, Donggala Regency.From the rainfall chart it can be seen that the average annual rainfall in the area varies with the highest rainfall occurring in January and the lowest in September with equatorial rain type.The Oldeman climate type for the Ogoamas rain post is E3 climate type with less than 3 wet months and 6 dry months.
The processed rainfall data above is then compared with the initial planting period (MT) data issued by the Ministry of Agriculture's Research and Development Agency.The MT issued consists of three parts in one year, namely MT1 for the first planting season in December, MT2 for the second planting season in April and MT3 for the third planting season in August.
From the results of a comparison of rainfall and planting time in 14 sub-districts, it was found that 2 sub-districts had sufficient rainfall (200 mm) to start rice planting.While the remaining 12 did not meet the criteria for sufficient rainfall to start planting rice for one year.By looking at the processed rainfall data, it can be seen that eventhough it has different types of rain, the climate types throughout Donggala Regency have the same pattern, namely the equatorial rain type.The equatorial rain type itself has a pattern where there are two peaks of rain during a year.From the comparison between rainfall and the beginning of the planting season in 14 sub-districts in Donggala Regency, it can be seen that as much as 31% of the beginning of the planting season corresponds to rainfall, while the remaining 69% does not meet the criteria for sufficient rainfall for rice cultivation.To overcome the lack of water during the planting season, it is necessary to maximize the function of irrigation in each sub-district, especially in areas with the Oldeman E climate type.
The Oldeman climate zone map that has been made based on the climate type of each rain post can describe the agro-climatic zone conditions in the Donggala Regency as a whole.The use of the Inverse Distance Weighted (IDW) method makes it easier for researchers to determine the distribution of climate types, especially in areas that do not have rain gauge posts.
The climate zone map display uses coloring to display differences in the distribution of climate types in all regions.In addition, a description of each climate type is also displayed in the legend column to make it easier for readers to understand the meaning of the colors on the map.

Conclusion
Based on the results of the analysis and discussion, the following conclusions can be drawn: Donggala Regency has 3 Oldeman climate types, namely type A in the Rio Pakava District with thesuitability of continuous rice cultivation but low production, B in the South Banawa and Sojol Districts with the suitability of continuous rice planting with high production when harvested in the dry season , type E in the Districts of Central Banawa, Banawa, Tanantovea, Labuan, Sindue, Sindue Tobata, Sindue Tombusabora, Balaesang, Balaesang Tanjung, North Sojol and Dampelas which is too dry, so it is possible to only plant one crop of crops.In areas with climate type E it is recommended to optimize irrigation water to meet the water needs of rice plants.The agro-climate zone map made using the Inverse distance weighted (IDW) interpolation method can describe the distribution of climate types as a whole, especially in areas where there are no rain measuring posts such as in Pinembani District.

3. 1 .
Research result 3.1.1.Rain post data.Rainfall data that was successfully collected and processed came from 15 BMKG rain measuring points spread across several sub-districts in the Donggala Regency area.The location of the rain post which is the source of data is shown more clearly in Figure 1 below.

Figure 1 .
Figure 1.Map of the distribution of rain gauge posts in Donggala Regency

Figure 2
Figure2of the average monthly rainfall data series from the Sindue rain post, Sindue District, Donggala Regency.The average annual rainfall in the area varies, with two rain peaks, namely June

3. 1 . 3 .
Oldeman climate type mapping.The agro-climatic zone map according to oldeman of Donggala Regency is shown in Figure2.Using the Inverse Distance Weighted (IDW) method, 15 scattered rain 8 heading points were then interpolated according to each climate type to see the distribution of climate types in Dongala Regency as a whole.

Figure 3 .
Figure 3. Map of agro-climatic zones according to Oldeman in Donggala District To dry, possible growing palawija one.Possible growing 1 season rice or 1 season palawijaRice onlu one and the socon for palawija and no rice at dry season One rice and twice palawija Growing rice twice of shorten live circkle, short dry season growing Palawija Suitable growing rice for year long Suitable growing rice for year long, but low production

Table 1 .
Suitability of climate types in Donggala Regency