Improvement of Tertiary Irrigation Networks, Changes in Cropping Patterns, and Increasing Cropping Index at Kendal Indonesia

Abstract

Increasing food crop production remains a top priority for the Indonesian government, as demand increases as the population grows. One of the obstacles faced in increasing production is climate change. One of the adaptations to climate change in agriculture is to establish policies for the development and modification of infrastructure that can save water resources management and establish institutions involved in the planning and implementation of water resources management. Kendal Regency, Central Java Province, is one of the regions that contributes to food availability in Indonesia. These conditions support the development of food crops, especially rice, corn, and soybeans. Since 2015, the government and farmers have made improvements to the tertiary irrigation network in paddy fields. This activity aims to increase the cropping index and achieve cropping patterns for one year. In the implementation of irrigation network improvement activities, the community of farmers using water usually works together in determining the location for repairs and making suggestions for improvements to the government. Improvements to irrigation networks were able to increase the cropping index by 0.37 from 1.85 in 2015 to 2.22 in 2016 or equivalent to an area of 8,880 ha (standard area ±24,000 ha).

1. Introduction

Raising food crop production remains the top priority for the government. This is done to meet the increasing food needs and the expanding number of people in Indonesia. One of the hindrances faced in increasing production is climate change. The world of agriculture is faced with more significant challenges, mainly due to global climate change, which impacts the area of sub-optimal land with more severe stress levels [1].

Climate change will have negative impacts on water resources, agriculture, forestry, health, and the vulnerability of public infrastructure, as well as the extinction of various species [2]. The area under rice cultivation that is nationally threatened with drought in the next one or two decades will increase from 0.3–1.4% to 3.1–7.8%, while the area that is unharvested due to drought will also increase from 0.04–0.41% to 0.04–1.87% [3]. On the other hand, the La Nina impact caused an increase in flood-prone cropping areas from 0.75–2.68% to 0.97–2.99%, and the area that is unharvested from 0.24–0.73% to 8.7–13.38%. As a result, the risk of decreasing food production, due to floods and droughts, will rise from 2.4–5.0% to more than 10% [4].

Survey activities for the improvement of tertiary irrigation networks intensively in irrigated rice fields in the Kendal Regency were carried out in 30 (thirty) villages spread over 11 (eleven) subdistricts. The survey location is in the form of agroecosystems of rice fields irrigated with technical irrigation networks and semi-technical irrigation networks.

2. River flow areas basic irrigation network improvement

2.1 Irrigation network to increase food production

Replace in anticipating the impacts of climate change, the government has set policies, such as developing and modifying infrastructure, that can save the management of water resources and biodiversity, taking into account the emissions trading, reducing greenhouse gases, and establishing institutions involved in planning and implementing water resources management, as well as innovations on the application of technology that has a good impact on water resources and other natural resources [5].

The irrigation system includes irrigation infrastructure, irrigation water, irrigation management, irrigation management institutions, and human resources [6]. The Important infrastructure to support the availability of water is the irrigation network. The availability of water will determine the success of increasing production. The water sufficiency for plants will provide optimal results for both growth and production [7]. Regarding food crops, the availability of water from technical irrigation networks (weirs, culverts, and reservoirs), as well as other water sources (dams/spring ponds, long storage, and others) is the basis for accelerating the increase in food and agricultural production [8].

Storage and utilization of abundant water is an applied operational strategy to increase food production in rain-fed rice fields [9]. In addition, through water management (utilizing rainwater and other water resources as much as possible), increasing food production in 4 million ha of distributed rain-fed rice fields in various islands can be done, including by increasing the cropping index from one to two or three times per production in a year [10, 11]. Moreover, the tertiary irrigation network restoration of rice fields can also increase the cropping index and production [12].

The rehabilitation of irrigation networks to optimize the water resources is mainly to support the establishment of food security, increase added value, and at the same time increase farmers' welfare [13]. The Indonesian government has rehabilitated the irrigation network with the realization of around 3.05 million hectares of rice fields that are spread across all agricultural areas in Indonesia [6].

Generally, the type of channel in the irrigation network is divided into primary, secondary, tertiary, quarter, and drainage channels [14]. Primary and secondary irrigation networks become the responsibility of the central, provincial, and district governments. Meanwhile, the maintenance of tertiary irrigation networks is accomplished by farmers or water management groups. The provision of optimal tertiary irrigation networks in irrigated rice fields is a direct and adaptive operational action that can be taken by farmers in dealing with drought or water needs. One of the main culprits of the food and agricultural production opportunities loss is the poor condition of supporting infrastructure.

The deterioration of the irrigation system network will threaten the increase in food production [6]. Restoration of damaged irrigation networks covering an area of 3 million ha or 52% of the total irrigation area, can expand irrigation services to increase the cropping index by 0.3 or more [8]. The network restoration is gradually carried out by the government and farmer groups. Irrigation management requires institutions, namely, management, members, and various accompanying regulations to be efficient in their use and remain sustainable [6]. The results of research in Central Sulawesi Indonesia recommend a more efficient and useful technology in dealing with climate change in food crop production to increase farmers' knowledge, provide user-oriented features, and various institutions to provide collaborative programs in facing the challenges of climate change [15].

2.2 Distribution of watersheds in Kendal Regency

Kendal Regency, Central Java Province, is one of the regions that contributes to food availability in Indonesia. Generally, Kendal Regency has an area of 23,270.07 ha of irrigated rice fields and 809.6 ha of rain-fed rice fields [16]. These conditions support the development of food crops, especially rice, corn, and soybeans. Efforts to increase food crop production can run optimally; therefore, since 2015, restorations have been made to tertiary irrigation networks in rice fields. Through the restoration of the irrigation network, it expects an integrated increase in IP and resource management with a specific location, as well as the application of technological innovations according to technical standards can also be carried out. Finally, the target of increasing production, productivity, and rice crop index in a year can be realized. One of the efforts made by the government to fulfill food needs is by increasing food production in agriculture. The most productive agricultural effort is the use of water for irrigation. Based on these conditions, proper, regular, and sufficient water supply and management is a must [13].

Irrigation can be interpreted as an effort to bring in water by making buildings and channels to drain water for agricultural purposes, distributing water to rice fields or farms regularly and in sufficient quantities, and then disposing of the unnecessary water is required [17]. Generally, irrigation areas are closely related to watersheds as sources of irrigation in the form of large rivers, springs, and others [18].

This watershed is usually associated with the local climate of a place, which is a rainfall area. In Kendal Regency, there are four groups of rainfall areas (Figure 1), namely, 500 mm/year rainfall, 1000 mm/year rainfall, 1500 mm/year rainfall, and 2000 mm/year rainfall. The highest rainfall (2000 mm/year) is in two subdistricts, namely, Plantungan and a small part of Sukorejo, 1500 mm/year is in Limbangan District, 1000 mm/year is in Boja, Singorojo, Patean, and parts of Sukorejo. The remaining 500 mm/year of rainfall occurs in most subdistricts in the Kendal Regency. These conditions determine the watershed and the construction of irrigation networks. For example, the Cepiring subdistrict is an irrigation area originating from the Bodri watershed or Sidomukti irrigation area (Figure 2).

Figure 1.

Map of rainfall in Kendal Regency [19].

Figure 2.

Irrigation network in Kendal Regency [19].

Based on the type of rainfall and watershed in the Kendal Regency, the construction of a tertiary irrigation network is displayed in Table 1.

No	Subdistrict	Village	Benefit recipients	Name of irrigation area
1	Boja	Bebengan	Rukun Tani	Sojomerto
2		Ngabean	Tani Mulyo II	Sojomerto
3		Trisobo	Tuk Mandiri I	Sojomerto
4	Brangsong	Brangsong	Gempolsari	Sojomerto
5		Kertomulyo	Sidomulyo	Sojomerto
6		Sidorejo	Sido Makmur	Sojomerto
7		Tosari	Tirto Arum	Sojomerto
8	Cepiring	Juwiring	Sido Maju	Sidomukti
9		Sidomulyo	Sido Maju	Sidomukti
10	Gemuh	Galih	Tirto Rahayu	Kd. Pengilon
11		Poncorejo	Lumintu	Kd. Pengilon
12		Sedayu	Tirto Sido Ayu	Kd. Pengilon
13		Triharjo	Sumber Rejeki	Kd. Pengilon
14	Kaliwungu Selatan	Plantaran	Ngudi Makmur III	Bodri Trompo
15		Sidomakmur	Tani Barokah	Bodri Trompo
16		Sukomulyo	Tirto Lestari	Bodri Trompo
17	Limbangan	Gonoharjo	Darmatirta	Sidomukti
18		Tamanrejo	Sumberrejo	Sidomukti
19	Ngampel	Dempelrejo	Sudi Makmur	Blimbing
20		Ngampel Kulon	Mugi Rahayu	Blimbing
21		Ngampel Wetan	Mugi Rahayu	Blimbing
22	Patean	Mlatiharjo	Mlati Tirto Mulyo	Mudal
23		Plososari	Tani Luhur	Mudal
24	Patebon	Donosari	Maju Makmur	Jlegong
25		Pidodo Kulon	Ngudi Makmur	Jlegong
26	Pegandon	Gubugsari	Gemah Ripah	Bodri Trompo
27		Karangmulyo	Tirto Mulyo	Bodri Trompo
28		Pesawahan	Sido Rukun	Bodri Trompo
29	Singorojo	Kaliputih	Ngudi Makmur	Bodri Trompo
30		Singorojo	Tirto Tlogosari	Bodri Trompo

Table 1.

Tertiary irrigation channels in Kendal Regency, Central Java Province.

Table 1 shows that there are 30 locations for the construction of tertiary irrigation channels in the Kendal Regency. These locations are spread over 11 subdistricts with different sources of irrigation water. Based on the table, it is known that seven sources of irrigation water or watersheds become the source of irrigation in the Kendal Regency.

Regarding the restoration of irrigation networks, the determination of the point of the tertiary irrigation network restoration is based on the watershed and the irrigation area that has the potential to increase the cropping index. The restoration of the tertiary irrigation network is not carried out in locations that are prone to flooding, whether it is rainwater puddles or seawater intrusion.

Figure 3 depicts that the northern coast (yellow) is a flood-prone area. Therefore, in the first planting season, the related agency suggested farmers plant rice varieties tolerant of flooding. If Figure 3 is combined with the position of the irrigation network in Figure 2, the Kendal Regency area is an area where the condition of the availability of irrigation water is very sufficient.

Figure 3.

Disaster-prone area in Kendal Regency [19].

The water requirement in rice cultivation is divided into several stages. Tillage is the stage that requires the most water. Optimal tillage is the beginning of preparation for plant life that affects the growth and production of rice plants. Therefore, water is absolutely necessary. Water requirements in each growing season are different. The water requirement for early maturing rice plants is highest in the second planting season because rainwater begins to decrease. The largest available water discharge occurs at the end of February and the potential for water availability is relatively small [20]. Therefore, in the second and third planting seasons, the expansion of water discharge through the tertiary irrigation network significantly affects the increase in the cropping index and the enlargement of rice fields, particularly in technically irrigated rice fields [13].

Water sufficiency for crops in a rotation pattern is the foremost step in considering whether a crop rotation is possible to be applied to an area. The irrigation planning criteria offer an effective rain calculation based on rainfall measurement data at the nearest station. In areas that have irrigation network facilities or irrigated rice fields, the water source is better used as chief support to irrigate crops than rain. A rational rotation pattern is selected based on the following criteria: (1) the need and sufficiency of water; (2) the highest economic profit each season per year; and (3) other considerations, such as market demand and government policies [21].

2.3 The restoration of the tertiary irrigation network in Kendal District

Irrigation network facilities and infrastructure restoration is divided into two activities, namely, development and maintenance. Related to these activities, there are many locations in irrigation areas that require first handling. The results of the research in Yogyakarta showed that the tendency of tertiary irrigation networks in 10 irrigation areas was that the higher the command area, the higher the priority ranking for the development or management of a location. If there are several proposed locations with similar conditions, prioritization can be determined based on the command area [22].

In Kendal Regency, the restoration of the tertiary irrigation network was conducted to support the enlargement of the planted area for food crops. The irrigation network restoration was conducted in 57 locations (Table 2), including in the Districts of Boja, Kaliwungu Selatan, Pegandon, Singorojo, Limbangan, Brangsong, Ngampel, Cepiring, Patebon, Patean, and Gemuh. The estimated area of irrigated rice fields is about 3500 ha. The restoration of the tertiary irrigation network is a shared commitment between the government and the water management groups. However, in practice, the officers of the union of water-user farmers usually work together in determining the location for repairs and making suggestions for restorations to the government.

2015 State Budget					2015 Revised State Budget
Sl. No.	Subdistrict	Village	Name of water-user farmer association	Area (Ha)	Subdistrict	Village	Name of water-user farmer association	Area (Ha)
1	Boja	Bebengan	Rukun Tani	35	Pageruyung	Bangunsari	Taru Martani	50
2		Ngabean	Tani Mulyo	30	Plantungan	Bendosari	Ngudi Sejahtera	80
3		Trisobo	Tuk Mandiri I	25	Ringinarum	Pagerdawung	Tirto Sebrumbun	70
4	Kaliwungu selatan	Plantaran	Ngudi Makmur III	80		Purworejo	Ringin Wangun II	70
5		Sidomakmur	Tani Barokah	70		Mojo	Tirto Agung	70
6		Sukomulyo	Tirto Lestari	80		Kedungsari	Sumber	70
7	Pegandon	Pesawahan	Sido Rukun	70	Cepiring	Podosari	Tirtosari	40
8		Karangmulyo	Tirto Mulyo	80		Korowelangkulon	Ngudi Rejeki	60
9		Gubugsari	Gemah Ripah	80	Gemuh	Sojomerto	Joyo Klantung	70
10	Singorojo	Singorojo	Tirto Tlogosari	70	Singorojo	Getas	Usaha Maju	60
11		Kali Putih	Ngudi Makmur II	80	Boja	Karangmanggis	Ngudi Rahayu	25
12	Limbangan	Gonoharjo	Sido Makmur	40		Blimbing	Dewi Sri Makmur	25
13		Tamanrejo	Sumberrejo	50		Bebengan	Tanjungsari	30
14	Brangsong	Kertomulyo	Sido Mulyo	70	Ngampel	Winong	Pengilon	70
15		Sidorejo	Sido Makmur	70		Sudi Payung	Sudi Makmur	70
16		Brangsong	Gempolsari	70	Patebon	Tambakrejo	Tirto Sari	40
17		Tosari	Tirto Arum	70		Pidodowetan	Mugi Langgeng	50
18	Ngampel	Dempelrejo	Sudi Makmur	80	Pegandon	Puguh	Tirto Panguripan	60
19		Ngampel Kulon	Mugi Rahayu I	80		Tegorejo	Dadi rejo	80
20		Ngampel Wetan	Mugi Rahayu II	70	Weleri	Ngasinan	Tirto Arum	70
21	Cepiring	Sidomulyo	Sido Maju	70		Karanganom	Loh Jinawi	70
22		Cepiring	Sido Maju	70		Sumberagung	Ngudi Luhur Sejati	70
23	Patebon	Donosari	Maju Makmur	60		Karangdowo	Tirto Asri	70
24		Pidodo Kulon	Ngudi Makmur	80	Kangkung	Gebanganom	Tani Makmur	60
25	Patean	Ploso Sari	Tani Luhur	50		Jungsemi	Sido Kabul	70
26		Mlatiharjo	Mlati Tirto Mulyo	50
27	Gemuh	Triharjo	Sumber Rejeki	80
28		Sedayu	Tirto Sido Ayu	80
29		Poncorejo	Lumintu	80
30		Galih	Tirto Rahayu	80
Area of irrigated rice field				2000				1500

Table 2.

Tertiary irrigation network repaired in the Kendal Regency in 2015.

The union of water-user farmers in the Bantimurung Irrigation Area, Maros Regency, South Sulawesi, Indonesia, has moderate authority in the utilization, development, and management of irrigation water [23]. Whereas in Morocco, farmer organizations formed to intervene in water management and sugar production appear to be inactive or have weak relationships with their constituents. Therefore, irrigation managers and the sugar industry continue to interact directly with farmers in a centralized manner [24].

The restoration of the tertiary irrigation network in the Kendal Regency was conducted in the areas of lowland, medium, and highland irrigated rice fields. In Figures 4 and 5, some examples of tertiary irrigation network restoration locations in the lowlands include Patebon Subdistricts (Maju Makmur water user farmer association covering an area of 60 ha), Pegandon (Gemah Ripah water user farmer association covering an area of 80 ha) and Gemuh (Tirto Rahayu water user farmer association covering an area of 80 ha and Sumber Rejeki water user farmer association covering an area of 80 ha).

Figure 4.

Secondary irrigation channels in Gubugsari Village, Pegandon District (not yet repaired), and tertiary irrigation networks in Gubugsari Village, Pegandon District.

Figure 5.

Secondary (no restoration) and tertiary channels in Galih Village, Triharjo Village, Gemuh District.

The restoration of the lowland tertiary irrigation network was also conducted in Weleri Subdistrict (Sumber Agung Village and Karanganom Village) and Kangkung Subdistrict, Gebanganom Village. The restoration of the tertiary irrigation network in Sumber Agung Village is an irrigation network from the Timbang Weir (Weleri District), which is a transfer from the Damar river. The cropping pattern that is usually done by farmers around the restoration of irrigation networks, in general, is paddy-paddy-paddy. But some farmers plant with paddy-paddy-tobacco or paddy-paddy-horticultural (vegetable) cropping patterns. Meanwhile, irrigation in Karanganom Village, Weleri District, comes from the Sasem Weir (from Grinsing District, Kendal Regency). The usual cropping pattern is paddy-paddy-paddy (Figure 6).

Figure 6.

Restoration of the Tertiary Irrigation Network at Ngudi Luhur water user farmer association Sejati, Sumberagung Village, Weleri District, and Timbang Weir, Weleri District.

For the area of Tani Makmur water-user farmer association Gebanganom Village, Kangkung District (Figure 7), the restoration of the tertiary irrigation network is adjacent to the secondary channel from the Juwero Weir (in Gemuh District). The initial cropping pattern was paddy-pady-corn. With the restoration of the tertiary irrigation network, it is expected that the cropping pattern will become paddy-paddy-paddy.

Figure 7.

Tertiary irrigation network rehabilitation at P3A Tani Makmur, Gebanganom Village, Kangkung District.

Restorations of the tertiary irrigation network in the highlands were conducted in the district of Boja (in Figure 8), water-user farmer association of Bebengan Village for an area of 35 ha, Tani Mulyo water-user farmer association (Ngabean Village) for an area of 30 ha and in Trisobo Village Tuk Mandiri I water-user farmer association for an area of 25 ha. In addition, restorations of the irrigation network were carried out at the location of Taru Martani water-user farmer association (in Figures 9 and 10, Bangunsari Village, Pageruyung District), as well as repairing the Kreon weir from the Kuto River, which was an aspiration fund. The cropping index around Kreon Weir is not rice, but annuals. It can be said that the restoration of the irrigation network around the Kreon Weir is to improve the irrigation of the rice fields under the Kreon Weir. Restorations to the irrigation network were executed in two places, namely, around the Kreon Weir and near the rice fields.

Figure 8.

Semi-technical tertiary irrigation channels in Bebengan Village and Ngabean Village, Boja District.

Figure 9.

The secondary irrigation channel has a disconnected position with a tertiary channel in Trisobo Village, Boja District.

Figure 10.

Kreon weir, irrigation network, and irrigated rice fields in Bangunsari Village, Pageruyung District.

Besides Pageruyung (Figure 11), other highland rice fields are located in Plantungan District. The restoration was carried out at Ngudi Sejahtera water-user farmer association, Bendosari Village, Plantungan District. This location is quite far and close to Batang Regency. The flow of water comes from the Bulus river, which is runoff from the Kuto River. The cropping pattern of irrigated rice fields is paddy-paddy-paddy. It can be said that the restoration of the irrigation network is to expand the area of rice fields that can be irrigated.

Figure 11.

The location of the irrigation network is in Bendosari Village, Plantungan District.

The restoration location is quite far from the rice fields. However, the land around the irrigation network, which was previously planted with annual crops, is expected to be planted with rice in the third planting season of the following year.

Based on the results of field observations and focused discussions with the agriculture, plantation, livestock, and forestry service of Kendal Regency (coordinator of instructors, agricultural assistants, instructors, and agricultural infrastructure staff) and farmers, information was obtained that the restoration of the tertiary irrigation network can reduce water loss due to leakage during irrigation. Therefore, the area of irrigated rice fields increases, especially in the second season of rice planting. In addition, farmers hope that the rice fields can be planted with food crops after the restorations of the tertiary irrigation network in the third planting season.

The implementation of irrigation network infrastructure development in Bengkulu Tengah Regency, Bengkulu Province, Indonesia, is a priority in supporting the provision of water resources, functioning to support dynamic and interactive rural development, as well as irrigated agriculture in the future. The utilization of water resources is fully aimed at improving the economy and welfare of farmers. By using technology it supports infrastructure development, as well as water management to produce a more effective irrigation network [25].

Small irrigation systems with a command area of less than 500 ha are the backbone of family food security, which, in turn, leads to food security at the national level. The deterioration of the irrigation system network will threaten the increase in food production. In the future, irrigation infrastructure must be supervised better. Therefore, the agricultural sector can realize agricultural diversification. The wider the conservation, local wisdom, and social capital in irrigation management can be maintained. Irrigation expansion and development should include the participation of farmers and water-user farmer association through self-management, not a tender system (auction), and target-oriented. In addition to better performance, the self-management system fosters a high sense of ownership and responsibility by the water-user farmer association [6].

Self-management will be more efficient if it is combined with a mutual cooperation system, therefore, restoration targets can be achieved and even exceeded. In addition, supervision from farmers and even cross-control between group members will automatically occur. In the future, the role of the water-user farmer association will be improved to increase the function of the development and management of irrigation, especially in small irrigation. Good small irrigation management involving the role of government and stakeholders is expected to improve farmers' income levels, expand job opportunities in farming and outside farming, food resources, soil and environmental damage prevention, and ownership of productive assets [6].

Participatory irrigation, where farmers are given greater control and management responsibility, has been a topic of controversy for many years. Initially seen as a panacea for dealing with weaknesses in state-run irrigation, participatory irrigation has generated mixed results, especially in south Asia. Part of the challenge in understanding the conditions that elevate and undermine participatory irrigation is that it is rarely deployed in the same way. For example, irrigation fees collected by farmers are not handled collectively, even within a single country. In some instances, a large amount of collected fees is retained locally. Only a small amount is kept for local use. In this paper, we use game theory to consider how the portion of irrigation fees retained locally might impact the effectiveness of participatory irrigation. We show that there are multiple plausible equilibria and that allowing farmers to retain more funds locally might shift behaviors from an uncooperative equilibrium to a cooperative outcome. However, we also find that it is unlikely to be a singular fix. We use empirical evidence to demonstrate the conundrums of making participatory irrigation sustainable [26]. Irrigation water can increase rice production, productivity, and farmers' revenue through the restoration of irrigation infrastructure, utilization of biological fertilizers, and proper management of irrigation systems [27].

3. Food production and tertiary irrigation improvement

The impact of constructing a tertiary irrigation network in the Kendal Regency can be seen in two things, the cropping index and productivity. The construction of irrigation networks can affect productivity and production [28]. Tertiary irrigation construction not only increases production by 22.19% but also increases the cropping index [29]. Generally, the impact of tertiary irrigation construction on cropping index and production in the Kendal Regency is illustrated in Figures 12 and 13.

Figure 12.

The effect of tertiary irrigation network construction on increasing IP in Kendal Regency in 2015–2020.

Figure 13.

The effect of tertiary irrigation network construction on rice and maize production in 2015–2020.

The picture above depicts that there was an increase in the cropping index of rice plants in 2016. This increase occurred after the restoration of the irrigation network in 2015. The increase in the cropping index occurred by 0.37 from 1.85 in 2015 to 2.22 in 2016 or equivalent to an area of 8.880 ha (standard area ±24,000 ha). However, in the following year until 2019, the rice planting index decreased to 0.73. Exploration of further information related to the decline in the index of rice cultivation was caused by the shift of commodities, which are usually paddy to corn, in several subdistricts, such as Brangsong, Patebon, Gemuh, and Ringinarum. Farmers said that the corn commodity in recent years was more promising both in terms of production and price. Therefore, corn was more profitable. The transfer of commodities conducted by farmers is in line with corn production in Kendal Regency as shown in Figure 13.

In Figure 13, rice production increased from 2015 was 44,305 tons to 53,363 tons (9.058 tons). However, from 2017 to 2019, there was a decrease to 35,642 tons. On the other hand, corn in 2016 increased in production by 13,609 tons, from 56,977 tons to 70.586 tons. Furthermore, corn production increased to 77,219 tons in 2017, in 2018 by 62,665 tons, in 2019 by 66,364 tons, and in 2020 by 72,015 tons. This condition is contrary to rice production which continued to decline until 2019 and rose again in 2020.

4. Conclusions

Improvement of the tertiary irrigation network is one of the adaptations to climate change for the farmer level. The improvement of the tertiary irrigation network is very much needed by farmers with further management carried out by the water-user farmer association. Improvements to the irrigation network have been carried out at 57 points and spread across all subdistricts from the lowlands, medium to highlands. The improvement of the tertiary irrigation network was able to increase the cropping index by 0.37, from 1.85 in 2015 to 2.22 in 2016, or equivalent to an area of 8,880 ha (standard area ±24,000 ha). The construction of irrigation networks was also able to increase production by 9,058 tons, from 44,305 tons in 2015 to 53,363 tons in 2016. In the following year (2017–2019), rice production decreased because farmers in several subdistricts switched commodities to corn. The role of water-user farmer associations in the improvement and optimal management of tertiary irrigation networks is very important. Thus, the management of water-user farmer associations must be regulated and functioned professionally in sustainable agricultural development in Indonesia.

Acknowledgments

Thank you to the staff of the Department of Agriculture, Plantation and Forestry, Kendal Regency, Central Java Province and farmers who have provided information about the construction and improvement of tertiary irrigation networks. Likewise, we would like to thank all the staff of the Central Java of Assessment Institute for Agricultural Technology who have assisted in this survey, especially Mrs. Endah Winarni.

The survey activity for the improvement of the tertiary irrigation network on irrigated rice fields in Kendal Regency, Central Java was financed by the Indonesian Agency for Agricultural Research and Development, Ministry of Agriculture.

Conflict of interest

The authors declare no conflict of interest.

Appendices and nomenclature

Indonesian farmers really need adaptation technology to climate change, especially farmers in paddy fields. One of the technologies for adapting to climate change is the improvement of tertiary irrigation networks in irrigated rice fields. The Indonesian government, especially the agriculture office, has data on irrigation networks (primary, secondary, and tertiary) and points for repairing tertiary irrigation networks. Determination of the point of improvement of the tertiary irrigation network is based on the possibility of primary and secondary irrigation networks, available water sources, and collaboration of water-user farmer associations and the government. Surveys of farmers using water after the improvement of the tertiary irrigation network show that the water source to meet the irrigation network greatly determines the commodities to be planted, the area of irrigation coverage, and the cropping index.