Abstract. Neswati R, Abdullah S, Musa Y, Nasaruddin. 2023. Assessing soil conservation techniques on sloping lands in the humid tropics area of Indonesia in the context of maize cultivation. Biodiversitas 24: 1686-1692. Sloping land is prone to severe erosion, particularly in areas with high precipitation, such as in humid tropics. In addition to slope and rain factors, crop management also influences soil erosion. This research aims to identify the most appropriate techniques to mitigate soil erosion by comparing three different techniques of maize (Zea mays L.) cultivation planted on sloping land in Indonesia's humid tropics. A field experiment was conducted in Gorontalo Regency, Gorontalo Province, Indonesia, in three maize growing seasons at a location with a slope of 15-30%. We used a split-plot design in a randomized block design, with the main factor being conservation techniques, namely no treatment (control) (K0), contour terrace (K1), strip cropping using Pennisetum purpureum Schumach. (K2) and alley cropping using Gliricidia sepium (Jacq.) Kunth (K3), and the side factor was Z. mays of two varieties: Mixed variety Arjuna BC (H1) and hybrid variety NK-33 (H2). The effects of each treatment were measured in term of soil erosion, and maize growth and productivity. The results showed that the strip cropping resulted in a lower erosion level compared to the contour terrace and alley cropping. However, erosion still exceeded the tolerable soil loss in all conservation techniques. The effects on the growth and production of maize of the two varieties in growing seasons 1, 2, and 3 were not statistically different (p<0.05). Maize production can reach >6 tons ha-1 in the two varieties planted and the value of the revenue to cost (R/C) ratio of all treatments ranged between 1.77 and 2.54. The results imply that the application of appropriate soil conservation methods has the potential to reduce erosion in the sloping land-humid tropics of Indonesia without compromising growth and productivity. However, it will take a longer period to reduce soil erosion significantly in a maize-based cultivation system on sloping land.

Background and Objective: Land productivity can be increased by optimizing land use and applying environmentally friendly technologies to achieve sustainable agriculture and one of them is intercropping.This study aims to analyze the growth and production of maize in the tropics of Indonesia's humid regions that utilize space under the coconut canopy.Materials and Methods: This study was carried out using a Randomized Block Design (RBD) where the treatment was given the combination of packages.The condition of the shade as the main plot consists of 3 levels namely; K0: Without coconut plants, K1: Shade of coconut plants aged 10-15 years and K2: Coconut plants >15 years.Plots were maize varieties namely; V1: Composite and V2: Hybrid.While plot children are fertilizing carried out in 3 stages, namely; F1: Fertilizing 100 kg urea haG 1 +200 kg NPK, F2: 150 kg urea+300 kg NPK and F3: 200 kg urea haG 1 +100 kg TSP/SP 36 haG 1 +50 kg KCl haG 1 .Results: The results showed that the age treatment of coconut plants had a very significant effect on plant height, number of rows per cob, production per hectare and weight of 1000 seeds.Variety treatment significantly affected the weight of 1000 seeds.Conclusion: Cultivation of maize in dry land intercropping with coconuts over 15 years old shows the economic feasibility with an average R/C ratio of 1.75 and monoculture maize cultivation (without coconut) has the best level of economic feasibility with an average R/C ratio of 1.94.

The presence of arbuscular mycorrhizae can vary in type and quantity which is determined by the environment. This study aims to explore and identify vesicular arbuscular mycorrhizae (VAM) in sugarcane plantations in tropical area of Indonesia. The method used was a quantitative survey that described the VAM characteristics and its morphology in sugarcane plantation. The Soil sampling were located at 3 provinces in Indonesia, namely, Takalar (South Sulawesi), Bombana (Southeast Sulawesi), and Gorontalo. The isolation of mycorrhizal fungi was carried out by extracting spores using the pour-filter according to Pacioni method, followed by centrifugation based on Brundrett method. The results of the soil samples from 3 different sugarcane plantations in Sulawesi island found 3 types of VAM namely, Acaulospora sp., Glomus sp., and Gigaspora sp. The highest number of VAM spores belonging to Acaulospora sp genus with small round shape was found in Takalar (South Sulawesi), while the lowest number was found in the soil samples of Bombana (Southeast Sulawesi) and Gorontalo sugarcane plantations. The VAM spores number and types on sugarcane plantation were commonly found in soil with high fertility than in nutrient-poor soil.

Background and Objectives: In Oxisols, soluble inorganic phosphorus is fixed by aluminium and iron.Humic substances is an extraction of organic matter contains functional compounds which could adsorp Al become organo-mineral.It could be more effective for time, cost and amount of organic matter by using humic substances.This study was conducted to improve phosphorus availability using humic substances from lignite and rice straw compost.Materials and Methods: The treatments consist of lignite 300 ppm (H1), lignite 600 ppm (H2), lignite 900 ppm (H3), straw compost 300 ppm (H4), straw compost 600 ppm (H5), straw compost 900 ppm (H6) with 3 replications using completely randomized design.The parameters measured in this study were some of the chemical properties of soil, mainly phosphorus availability and plants growth.Results: The findings suggested that the humic substances could altered soil chemical properties and the humic substances from rice straw compost 900 ppm is the most effective increased available phosphorus, soil pH, CEC of clay, C-organic and decreasing exchangeable aluminium.But, based on maize growth results such as plants height and dry matter weight, the plants still showed phosphorus deficiency symptoms.Conclusion: These results indicated that needed higher dose of humic substances above 900 ppm to fixed the chemical properties of Oxisols.Humic substances from rice straw compost more effective than lignite to improve available phosphorus in Oxisols.