Coastal acid-sulfate soils are crucial for producing crops and thus, for food security. However, over time, these soil resources experience degradation, leading to higher agro-input, lower yields, and environmental hazards that finally threaten food security. The optimal use of this fragile resource is only attained by implementing vigorous integrated water–soil–crop management technologies amid the climate change impact. This study aimed to review the distribution, properties, use, and management of acid-sulfate soils in Kalimantan, Indonesia. Acid-sulfate soils cover about 3.5 Mha of the coastal area in Kalimantan and have high acidity, high-risk iron and aluminum toxicity, and low fertility, requiring precise water management, amelioration and fertilizer application, crop variety selection, and rice cultivation technologies. Lime, biochar, organic fertilizer, compost, ash, and fly ash are ameliorants that raise pH, reduce iron and aluminum toxicity, and improve crop yield. Rice cultivation has developed from traditional to modern but needs re-designing to fit local conditions. Depending on the soil nutrient status, rice cultivation requires 80–200 kg ha⁻¹ of urea, 50–150 kg ha⁻¹ of SP36, 50–150 kg ha⁻¹ of KCl, and 125–400 kg ha⁻¹ of NPK compound fertilizer, but is affected by CH₄ and CO₂ emissions. Good water management impacts the effective implementation of amelioration and fertilizer application technologies. The remaining challenges and future directions for water management, amelioration, fertilizer application, crop varieties, cultivation techniques, land use optimization, climate change adaptation and mitigation, technology adoption and implementation, and resource conservation are outlined. Acid-sulfate soils remain a resource capital that supports food security regionally and nationally in Indonesia.

The wetland agroecosystem in South Kalimantan is very diverse and mostly is sub-optimal land such as rainfed area of 172,074 ha, tidal swamp 188,908 ha, swamp area 135,504 ha, while irrigated paddy fields are only 55,116 ha. Paddy fields that have been planted with rice and can be harvested in 2017 covering an area of 506,126 ha with average productivity of 4.46 t / ha resulting in a total grain of 2,258,261 tons. The productivity of lowland rice in South Kalimantan is still below the average national rice productivity which reaches 5.18 t/ha. The constraints on the production of wetland rice in South Kalimantan vary depending on the type of land such as fluctuations in water (flooding, droughts), acid soils, the presence of toxicity of elements, not yet optimal water management in the swamps land, drought, nutrient deficiency in rainfed land. The area of upland rice plantations in the dryland of South Kalimantan is 63,170 ha, generally local varieties with average productivity of 3.07 t/ha. The development obstacles of upland rice in dry land include soil acidity, low organic matter, nutrient deficiency, competition in land use with other food crops and plantation crops. Rice production in South Kalimantan still has the opportunity to increase in the planting area and productivity. With the gap exist between rice productivity and the potential yield of new superior varieties, the use of other cultivation technologies application still provide opportunities to increase rice productivity in South Kalimantan. The addition of lowland rice planting area can be done by utilizing un-cultivated paddy fields (74,817 ha), the increase in planting index (PI) which is still low (PI 200 is only 9.14%). The addition of upland rice fields can be done on dry land fields with an area of 345,669 ha, or intercropping on plantation land (rubber, oil palm) that has not yet produced (183,539 ha).

Salvinia sp. is an alternative aquatic plant that is abundant in the swamplands and can be used for bioremediation of water contaminated with metals. The objectives of the experiment were (1) to evaluate the adaptation of Salvinia sp. to the iron (Fe) concentration in nutrient solution and tidal swampland soil growing medium and (2) to obtain Fe-adaptive Salvinia sp. as indicated by having rapid growth and high biomass. The experiment has been carried out in Cikabayan greenhouse IPB University, Bogor. Salvinia sp. was evaluated in a 4-liter plastic container with Hoagland nutrient solution that was supplemented with Fe based on the experimental treatments. The 10 accessions of Salvinia sp. were selected and evaluated using a pot filled with soil from tidal swampland. The results showed that increasing Fe concentration from 7 to 14ppm in solution inhibited the growth, reduced the fresh weight, and delayed the doubling time of Salvinia sp. The selection of Salvinia sp. on 7ppm Fe obtained 4 Salvinia sp. accessions with high biomass weights and fast doubling time, namely S. Kambat, Murung Karamat, Gambut, and Muning Tengah. Among the 4 accessions, the best two were S. Kambat and Murung Karamat with a fast doubling time of about 7.9 days and were adaptive in the tidal swampland.

Indonesia’s 8.92 million hectares of tidal wetlands have significant potential for rice production; however, varying soil nutrient status remains a major constraint to productivity. Fertilization practices that are inconsistent with soil nutrient status result in suboptimal yields. This study aimed to (1) identify key nutrients limiting rice yield and (2) develop an optimal site-specific fertilization package for tidal wetland rice systems. Field experiments were conducted in Murung Karamat and Danda Jaya villages, Barito Kuala Regency, South Kalimantan. The results indicated that nitrogen (N) and potassium (K) were the primary yield-limiting nutrients. Nitrogen omission reduced rice yields by 30.4% (1.17 t ha ^-1 ) in Murung Karamat and 19.8% (0.95 t ha ^-1 ) in Danda Jaya, while potassium omission reduced yields by 18.7% (0.88 t ha ^-1 ) and 7.5% (0.40 t ha ^-1 ). The implementation of site-specific nutrient management has significantly increased rice productivity. In Murung Karamat, yield increases of 0.94 t ha ^-1 (21.4%) and 0.88 t ha ^-1 (20.0%) were achieved through the Rice Crop Manager (RCM) and the Swamp Soil Test Kit (SSTK). In Danda Jaya, RCM increased yields by 16.3% compared with farmer practices. These results demonstrate that precision fertilization, supported by decision-support tools such as the RCM and SSTK, can significantly increase rice yields in tidal wetland environments. RCM and SSTK show strong potential as decision-support tools for site-specific fertilization in tidal wetland rice cultivation.

Lowlands in South Kalimantan are only about 54,455 ha (9.9%) of the total rice field area of 549,988 ha, most of them are irrigated paddy field that has been planted twice. The average productivity of rice in South Kalimantan is still low, which is around 4.46 t/ha milled dry grain. Rice productivity can be increased by the use of new high yielding varieties. In paddy fields, the use of new high yielding varieties with 2 seasons plantations is expected to increase rice production in the 2017 year in South Kalimantan which produces 2.25 million tons of rice. To find out the adaptation and yield of high-yielding rice, a study has just been carried out in rice fields in South Kalimantan. The activity was carried out in the village of Harapan Masa, Tapin Selatan sub-district, South Kalimantan district during the two planting seasons: Rainy season 2015/2016 and dry season 2016. Rice planted in rainy season 2015/2016 are varieties of Inpari-9, Inpari-20, inpari-21, and inpari-31, while in the dry season 2016 are varieties of Inpari-9, Inpari-30, inpari-31 and inpari-33. The results of the study showed that the average yield in the rainy season was higher (7.05 t/ha) compared to the results in the dry season 6.47 t/ha). In the rainy season, the highest yield was obtained in the Inpari-31 variety (7.95 t/ha), while in the dry season the highest grain yield was obtained by the Inpari-30 variety (6.99 t/ha). Inpari-9 and Inpari-31 varieties which were planted in the rainy season yielded higher yields of 7.30 t/ha and 7.95 t/ha respectively compared to those planted in the dry season of 6.29 t/ha and 6.19 t / ha.