Land expansion to meet productivity is often carried out without further consideration or study of the condition of the land. Insufficient soil quality leads to a decline in plant productivity. This research examines the soil conditions on sugar cane plantations in Takalar, Indonesia. We partitioned a single hectare of land into nine distinct observation plots to assess and compare the homogeneity of soil conditions and plant growth within each plot. In this study, we measured the organic carbon and the physical properties of the soil (bulk density and soil permeability), which are the main characteristics that reflect soil conditions in an area. Plant growth parameters such as the number of sugarcane tillers, height, and diameter were measured to compare growth in each plant plot. The research findings indicated that low organic C content values signified a lack of nutrient availability in the soil due to low soil permeability, resulting in a 50% reduction in production. These findings validated the shallow and marginal soil conditions. While soil processing demonstrated a capacity to decrease bulk density at depths of 15-30 cm, it proved ineffective in enhancing soil permeability. Post -tillage, the soil permeability rate at 0-15 and 15-30 cm depths declined, leading to compromised plant growth. Sugarcane plants in Takalar exhibited below-average growth with insuffi cient plant height (below 200 cm), stem diameter (less than 3 cm), and a low stem count per meter at the initial growth stage. Low organic C content values indicated a lack of nutrient availability in the soil due to low soil permeability, resulting in a 50% reduction in production. This research can be a reference for further research regarding improving soil quality and plant productivity.

This study examined the relationship between the decline in sugarcane productivity and the distribution of macropores and depth of root penetration in sugarcane plantations in Takalar during one planting period (October 2021-September 2022). There were five observation points (P1, P2, P3, P4, and P5) in one hectare of land to measure the distribution of soil macropores using methylene blue solution. Cross-sections of the soil were made to observe the presence of plant roots at a depth of 0-40 cm with a width of 60 cm. In each plot, disturbed soil samples were collected to measure soil texture, soil organic matter (SOM), nitrogen (N), phosphorus (P), and potassium (K) contents. Other measurement parameters were the infiltration rate and plant productivity. The results indicated that SOM and NPK levels at the research location were deficient, serving as the first indicators of problematic soil. Macropore observations revealed that macropores were distributed only at a less than 10 cm soil depth. This distribution limited the penetration of plant roots to a depth of 0-40 cm. The root length density (RLD) value indicated the absence of roots at depths of 30-40 cm in plots P2 and P3. The field findings explained why sugarcane production in Takalar only achieved 50%, around 40 t ha-1 from the first ratoon sugarcane harvest, instead of the expected 70-80 t ha-1.

Marginal soil with low nutrient content is a crucial problem in reducing crop productivity, including sugarcane. This study aimed to elucidate the possible improvement of the physical and chemical properties of marginal soil through the application of organic waste from sugar factories, namely kettle ash and press mud. Nine treatment combinations of 0, 10, and 20 t ha-1 of each kettle ash and press mud were arranged in a two-factor randomized factorial design with three replications. Soil organic matter, N, P, and K, soil aggregate stability, and sugarcane productivity were measured after planting sugarcane for five months. The results showed that the application of kettle ash and press mud, especially with a ratio of 20 t ha-1 kettle ash and 10 t ha-1 press mud, was able to reduce the leaching of organic matter and improve sugarcane growth, particularly increasing the number of tillers by 16%, stem height by 14%, and diameter by 16%. The sugarcane productivity obtained was 58.02 t ha-1. Other portions of kettle ash and press mud did not have a favorable effect on sugarcane productivity. This study provided practical insights for increasing agricultural productivity, especially in sugarcane plantations.

The germination and sprouting phases of sugar cane are critical periods that determine productivity. This phase occurs when the sugar cane is 1-3 months old and requires an adequate supply of water to support the formation of shoots. Poor soil conditions and high rainfall can cause the failure of bud formation. This study aims to determine the relationship between rainfall and soil permeability in successfully constructing sugarcane shoots. We divided the 1 ha research area into nine points (A, B, C, D, E, F, G, H, I) to observe plant growth and soil permeability. The growth factors measured included the number of stems, diameter, and plant height, measured by zigzag. Intact soil samples at a 0-15 cm depth were then analyzed in the laboratory using Darcy’s law to determine the value of soil permeability. The results showed variations in sugarcane growth in the nine study plots. The average number of sugarcane stalks is eight stalks/meter with a height of 159 cm and a diameter of 3 cm. The low soil permeability value of 0.13-0.5 cm/hour cannot compensate for the average rainfall during the budding phase, thereby suppressing plant growth by up to 50% of the average productivity that should be.

Conventional lowland rice cultivation involves flooding the paddy from planting to close to harvest, and high N fertilization. This practice leads to large amount of methane emissions. We studied the effect of soil water regime control on methane gas emissions and growth of several rice varieties on clayey soil. The experiment was arranged according to Split Plot Design. The main plot was water regime, i.e. continuous flooding (2-cm inundation), and intermittent flooding (flooded 2 cm then allowed to dry until the soil started to cracks). The sub-plots consisted of 3 rice varieties, i.e. Inpari 32, Mekongga, and Cisadane. Together, there were six treatment combinations, repeated 4 times. We measured methane emission, plant height, number of tillers per clump, number of productive tillers, and root volume. We computed analysis of variance, then performed Duncan Multiple Range Test. We found, at 57 and 73 days after planting, continuous flooding resulted in much (statistically) higher methane gas emissions than intermittent flooding (about 2 times greater for both Inpari and Cisadane, and 5 times greater for Mekongga). The two water regimes examined did not result in differences in plant height, number of tillers, productive tillers and root volume of the three varieties, although the flooded treatment tended to slightly give taller plant, more tillers and productive tillers. In conclusion, intermittent flooding significantly suppresses methane emission compared to continuous flooding. However, certain rice variety produces more methane than others. While intermittent flooding reduced methane emission, it did not statistically affect rice growth compared to continuous flooding.

Gender equality is one of the UN sustainable development goals less discussed in soil science in Indonesia. There is limited information regarding soil science education, and the role of women in Indonesia. This study aimed to provide an overview of the issue of gender equality in Indonesian soil science. We surveyed the number of women soil science students, lecturers, and researchers from 2016 to 2020. Twenty-seven soil science undergraduate programs were identified across government-owned universities in Indonesia. The number of students in soil science is steadily increasing in the last five years, each year with about 1500 new students enroll in soil science. The number of female students also increased with an average proportion of 55% in 2020. However, the number of women academics was only 30%, representing a disproportion of gender equity. The Indonesian soil science society had 35% women members. Students still perceive soil science would be better taught by men lecturers as it involves fieldwork. Nevertheless, more students preferred to be supervised by women lecturers. Our data also revealed that women academics had less opportunity to receive Ph.D. degrees, became professors, and occupied leadership positions in the university. We discuss barriers that hinder women's academics careers in Indonesia, including social and cultural values and organizational barriers. Soil science academics should prepare a gender-equal soil science workforce to the growing population. Thus, supporting the Indonesian soil scientists' women and achieving a more gender balance target is vital for accelerating soil science education, enhancing research opportunities, and managing agriculture to support economic growth.

Cocoa fine roots are responsive to changes in the soil environment to maximize nutrient and water absorption for plant growth. The presence of rock increases soil density and decreases available water content, promoting modification of fine root development. The purpose of this study was to clarify the effect of the physical properties of stony soil on the morphological properties of fine roots. In three land-use systems, soil samples were taken from four depths using a sample core measuring 385 cm3 in three land-use systems. Fine roots were extracted by the immersion method, to measure the length of fine roots from five classes of orders based on diameter. We notes, the bulk density of stony soil increases as the rock mass increases, and the depth increases. The available water content decreases with the increase in bulk density, and this decrease is more pronounced in the lower soil layer. Fine root length was found more in the lower order diameter class, decreasing soil moisture against the bulk density gradient. The bulk density in the topsoil layer reaches 1.71 g cm-3, increasing to 1.84 g cm-3 in the lower soil layer. It seems unreasonable, when compared to the general density of soil mass. Still, this result is solely due to the high fraction of rock with a higher density. Fine roots were dominated by orders 1 and 2 with root diameters < 0.25 mm and < 0.50 mm, reaching 70% of the total fine root length. Fine roots in this diameter class act as absorbent roots, acquiring water and nutrients from the soil.

Abstract. Saleh AR, Gusli S, Ala A, Neswati R, Sudewi S. 2021. Tree density impact on growth, roots length density, and yield in agroforestry based cocoa. Biodiversitas 23: 496-506. Cocoa-based agroforestry systems using langsat trees as shade is aimed to maximize the absorptions of solar energy, water, and nutrients, and increase income sources for farmers. Limited information about interspecific interactions between cocoa and langsat which is needed to improve the performance of agroforestry systems is a challenging idea. We studied the relationship characteristics of cocoa trees as a present shaded effect in the agroforestry system. Compared agroforestry systems were based on ages, namely young and old cocoa agroforestry or YCAF and OCAF, and monoculture systems (Mono) regardless of plant age. On above stony soil, we observed root length density (RLD) of cocoa and langsat fine roots, from under cocoa canopy to three distance levels from the cocoa stem (i.e. at a distance 0.4 m, 1.2 m and, 1.7 m), and four distance depths for all systems (i.e. at a depth 0-10 cm, 10-20 cm, 20-30 cm and, 30-40 cm). Stem diameter, basal area, canopy cover, yield cocoa beans, and convertible products non-cocoa were equivalent to the price of cocoa beans by tree equivalent yield (TEY) formula. Cocoa RLD in the Mono system did not differ from RLD-cocoa in the OCAF system, but both significantly differed with RLD-cocoa in the YCAF system. Shade trees increased tree density in both agroforestry systems, triggering competition in the canopy for sunlight. Expansion of langsat roots that spread closer to the cocoa trunk increased competition for nutrients and water. Both cocoa and langsat roots overlapped, exploring the same area. The yield of cocoa beans harvested by farmers from the YCAF and OCAF systems decreased by 50%. However, the langsat tree and several other species were accounted for 50% of the TEY in the agroforestry system, thereby adding a source of income to farmers is equivalent to the yield of cocoa beans from a monoculture system.

Many smallholder cocoa farmers in Polman, West Sulawesi-Indonesia breed goats traditionally on hilltop of the sloped cocoa farms. The goat’s manure is deposited under the pens, not distributed on the farm. We investigated the significance of this traditional goat breeding on the hilltop of sloping cocoa farms on soil quality based on the distance from the pens along the slope direction. We selected three sloped-cocoa farms where this traditional model had been practiced for years. The farms studied had 30 to 70% slopes, clay loam to clay soil textures. Along a transect lane, 0-5, 5-10, and 10-15 meters from the pen on each farm, we measured soil bulk density, hydraulic conductivity (HC), soil organic carbon (SOC), pH, soil nitrogen, phosphorus, potassium, cation exchangeable capacity (CEC) and earthworm population. This traditional practice improved soil quality compared to the adjacent farms which were not affected by the practice (control). Soil HC, SOC, N, P, K and CEC, and earthworm population were markedly higher under this system compared to the control, especially at 0 to 5 m distance from the manure deposit. The beneficial effects of this system were limited only within 10 m from the pens, beyond which soil quality was practically similar to the control site. This traditional system may be considered as an appropriate practice for soil quality maintenance in sloping cocoa farm, but an improvement is needed for greater benefits and reduced risks through terrace construction and manure deposition every 5-10 m range along the slope.

Biochar enriched with alginate-producing bacteria increases the ability of the soil to retain air so that it is available for the growth and production of maize in dry land. Pot experiments with mixed clay media with three types of biochar from oil palm shells, oil palm empty fruit bunches and corncob were conducted to study the interaction of biochar and alginate-producing bacteria (alginate production, phosphate solvent and nitrogen fixation) water (100%, 80% and 60%) on the growth of corn plants. Experimental results prove biochar factors, alginate-producing bacterial isolates and field capacity differ significantly from the vegetative phase of corn. Biochar interaction of corncobs with water at 100% lands capacity produces the best crops, but produces leaf area at 80% field capacity. While the interaction of corncob biochar with N-binding bacterial isolates produced the highest number of leaves. Correlation between variables that use role, biochar on the efficiency of water use for maize growth, where plant height, leaf number, leaf number and dry weight are negatively correlated with KAKL. This study provides the latest synthesis to discuss the use of biochar and bacteria as a strategy to increase support for food production of dry land that increases degradation.

This study aims to study the physicochemical characteristics of biochar produced from agricultural waste (palm kernel shells, empty fruit bunches and corn cobs), and its changes after being treated with alginate-producing bacterial isolates. After inoculation of the alginate-producing bacterial isolate coded KK1-40 for 28 days, biochar characterization was carried out which included surface functional groups and biochar structures (porosity and crystal) using FTIR and XRD, respectively. The results showed that the bacterial isolate KK1-40 changed the surface of the biochar by shifting the value of the hydroxyl (O-H) carboxyl (C = O) band, aromatic rings (C = C) and alcohol. Inoculation of bacterial isolates in biochar improved the structure and aromatics of oil palm shell and empty fruit bunches and increased porosity through hexagonal changes and 002 diffraction.From this study, it can be concluded that biochar stabilization in the soil is influenced by alginate-producing bacteria introduced into biochar products. This study presents a new biochar structure modification through in-situ biopolymer-based activation, so that it is more effectively used as a soil amendment that leads to improved agricultural land.

Abstract. Sukmawati, Ala A, Patandjengi B, Gusli S. 2020. Exploring of promising bacteria from the rhizosphere of maize, cocoa and lamtoro. Biodiversitas 21: 5665-5673. Alginate-producing bacteria are important for improving the quality of dry land, as they can both dissolve phosphate and fix nitrogen. Until now, the alginate-producing bacteria are largely isolated from seaweed. These bacteria were from the root ecosystem of cultivated plants. This study was conducted to explore bacteria that were capable of producing alginates, dissolving phosphates, and fixing nitrogen from the rhizosphere of corn (Zea mays), cocoa (Theobroma cacao), and lamtoro (Leucaena leucocephala). The characterization was carried out both morphologically and physiologically. A total of 17 isolates were successfully grown on alginate media, of which six isolates were from maize rhizosphere, five isolates from cocoa, and six isolates from the lamtoro rhizosphere. Bacterial isolates from the rhizosphere of maize and cocoa varied in terms of colony colors. In contrast, isolates from the lamtoro rhizosphere varied in colony forms. The KK1-40 isolates showed the highest cell biomass and dry weight which were 0.082 g mL-1 and 0.068 g respectively. The KK3-32 isolate showed the highest phosphate dissolution concentration of 10.85 mg L-1 with phosphate solubility efficiency value (PSE) and phosphate solubility index (PSI) which were 166.7 and a phosphate solubility index (PSI) 2.67 with a phosphate dissolution concentration of 10.85 mg L-1. LR1-25 isolates were able to fix the highest amount of nitrogen with a total N content of 0.36%. Isolates KK1-40 and LR1-25 were identified as Gram-negative bacteria and isolate KK-32 were identified as Gram-positive bacteria. The bacterial isolates KK1-40, KK3-32, and LR1-25 were superior bacteria that can be formulated to increase the productivity of dry land.

Belowground roles of agroforestry in climate change mitigation (C storage) and adaptation (reduced vulnerability to drought) are less obvious than easy-to-measure aspects aboveground. Documentation on these roles is lacking. We quantified the organic C concentration (Corg) and soil physical properties in a mountainous landscape in Sulawesi (Indonesia) for five land cover types: secondary forest (SF), multistrata cocoa–based agroforestry (CAF) aged 4–5 years (CAF4), 10–12 years (CAF10), 17–34 years (CAF17), and multistrata (mixed fruit and timber) agroforest (MAF45) aged 45–68 years. With four replicate plots per cover type, we measured five pools of C-stock according to IPCC guidelines, soil bulk density (BD), macro porosity (MP), hydraulic conductivity (Ks), and available water capacity of the soil (AWC). The highest C-stock, in SF, was around 320 Mg ha−1, the lowest, 74 Mg ha−1, was in CAF4, with the older agroforestry systems being intermediate with 120 to 150 Mg ha−1. Soil compaction after forest conversion led to increased BD and reduced MP, Ks, and AWC. Older agroforestry partly recovered buffering: AWC per m of rooted soil profile increased by 5.7 mm per unit (g kg−1) increase of Corg. The restored AWC can support about a week’s worth of evapotranspiration without rain, assisting in climate change adaptation.

Soil changes matter for the global carbon (C) balance although belowground response to land use change is slower and less obvious than that aboveground. Impacts of changes from natural forest to a range of intermediate tree-based land uses ('agroforestry') and non-tree agriculture remain contested. Standard C-stock accounting for a fixed sampling depth depends on changes in both C-org concentrations and bulk density, often with opposite effects. Confounding factors that, beyond current vegetation, influence C-org (soil texture, minerology, drainage, elevation and soil pH) may also influence bulk density. Because land use may not be random with respect to inherent soil properties, differences in soil C-stock between land uses can have multiple causes. We compiled and analysed data from six landscapes in Indonesia (volcanic and other mineral soils; Sumatra, Kalimantan; Java, Sulawesi) where chronosequences of forest, various agroforestry systems and open-field agriculture had been sampled. Our data analysis (617 samples within 0 - 30 cm depth; 8 land use types) showed that a pedotransfer function for effects on C-org of texture, elevation and soil pH reduced the relative standard error of means per land use type, reduced the range (Max-Min)/Avg and led to a more consistent pattern in apparent land use effects. Relative to natural forest reductions in C-org concentration in the 0-30 cm layer (corrected for confounding factors) averaged 8-20 % in degraded forest, complex agroforest, oil palm plantations and older forest plantation plots, and 25-30 % in simple agroforestry, monoculture tree crops and woodlots, or over 40 % in non-tree (mostly cropped) plots. However, calculated C-stock change was small due to an observed increase (up to 30 %) of bulk density relative to that of natural forest. This implies that up to 23 % additional C-org became included in the soil sampling, resulting in a non-negligible bias (underestimate) in estimated soil carbon loss based on internationally agreed C-stock accounting.

We report on the construction and operation of a laboratory rainfall simulator capable of producing rainfall of variable raindrop kinetic energy flux at the soil surface by varying raindrop size, drop height and rainfall intensity. The simulator was designed to study breakdown of soil aggregates during simulated rainfall under conditions of variable soil and rainfall factors. During tests, eight soil samples, 104 mm in diameter and 50 mm deep were accommodated on drained beds with controlled suction at the base (drainage). Ponded water on the soil surface was removed by suction (runoff), preventing interaction between water on the surface and rain. Depth of rainfall, runoff and drainage were measured to within 0.5 mm, at 1 min intervals, by electronic sensors and the data stored in a computer. The soil samples were surrounded by a large drained bed covered with a thin layer of test soil which served as an exchange bed, preventing splash loss of surface material from the sample during rainfall tests. These features enabled small quantities of soils to be tested under simulated field conditions (absence of ponding, profile drainage, no net loss of surface soil) without the complex interactions between applied rain and the artifactual effects of ponded surface water and excessively saturated soil often present in field and laboratory simulators with undrained target areas.

SummaryThe strength of soils is related to structural stability. Aggregate structure which collapses on wetting may set to a hard, consolidated layer on drying (hard setting). This process may be moderated by suction wetting and possibly by application of calcium, but the mechanism of moderation is not clear. We investigated the collapse‐strength relationship and the mechanism by which wetting method and calcium act to reduce strength in hard setting and non‐hard setting soils. Indirect tensile strength of aggregate beds that had been wetted with water or 10mM CaCI2 by rapid flooding or at a suction of 200 mm, was measured after draining to various suctions and drying at 40°C.The greater the volume strain during wetting and draining, the greater the tensile strength. Beds that were suction wetted, either with water or calcium solution, showed minimal collapse and did not develop high strength on drying. Water‐flooded beds had the greatest dry strength while beds flooded with calcium solution developed significantly lower strength. The critical factor determining tensile strength of the beds appeared to be the presence of large (>75 μm diameter) pores. The greater the volume strain on wetting, the smaller the proportion of larger pores and the greater the tensile strength on drying. Flood wetting caused more loss of large pores and closer packing of particles. Wetting with calcium solution did not affect the degree of collapse compared with that of water alone but did produce beds with larger pores than when wetted with water. Consequently the strength of the calcium‐wetted beds was lower.