Soybean (Glycine max (L.) Merril) is a food and industrial crop and a base for agricultural production. Adding organic material can increase plant growth and produce high yields. One of the organic materials that can be used is palm oil mill solid waste, specifically solid decanter cake (DC). However, the results showed that DC could only substitute 50 per cent of chemical fertilisers. DC must be combined with other materials, specifically Plant Growth plant-promoting rhizobacteria (PGPR), to maximise its benefits. PGPR is a group of bacteria that live in the plant rhizosphere and actively function as biofertilisers, biostimulants, and bioprotectants. Combining DC and PGPR is necessary because they have a mutually beneficial relationship, as DC is an organic material that can provide the nutrients PGPR bacteria need. This research will evaluate whether the collaboration of DC and PGPR can increase soybean growth and yield in ultisols using a Randomized Block Design. Combining decanter cake (DC) with a PGPR concentration can enhance soybean growth and yield. Soybean plants treated with 15-ton ha-1 + 50% PGPR DC tend to have the highest number of leaves, plant height, and number of branches, but DC 10-ton, ha-1 + 30% PGPR, has an equivalent effect. The treatment of 10 tons per hectare of decanter cake with 30% PGPR concentration tended to have the highest number of pods and yield.

One of the efforts to increase the production of oil palm flower bunches in ultisols is applying biofertilizers and inorganic fertilizers. Biofertilizers can reduce the use and adverse effects of inorganic fertilizers. Arbuscular Mycorrhizal Fungi (AMF) is one of the biofertilizers that can help plants absorb nutrients and increase plant resistance to various environmental stresses. This study aimed to examine the role of AMF (as biofertilizer) and inorganic fertilizers in increasing the production of oil palm flower bunches in Ultisol. This experiment is a factorial experiment using a Randomized Block Design. The first factor is the application of biofertilizers, which consists of two levels without biofertilizers (AMF) and with biofertilizers (AMF). The second factor is the dose of inorganic fertilizer, composed of 5 levels, no inorganic fertilizer, 25, 50, 75, and 100% recommended doses of inorganic fertilizer. The variables observed were the number of sheaths, the percentage of broken sheaths, the number of male flower bunches, the number of female flower bunches, the percentage of male and female flower bunches, sex ratio per plant, and AMF colonization. The results showed that AMF biofertilizer saved 25% of inorganic fertilizers and increased 29.33% of female flowers production. The highest production of oil palm flower bunches was obtained from the application of AMF biofertilizer and 75% of inorganic fertilizers (1.5 kg Urea, 1.1 kg SP-36, 1.2 kg MOP, 0.7 kg Kisserite per plant). Oil palm with AMF had a higher average sex ratio than plants without AMF biofertilizers. The average sex ratio in oil palm plants applying AMF biofertilizer and inorganic fertilizers ranged from 0.42 to 0.73.

Soybean is planted in some types of land agroecology, but production centers are mostly on peat and tides. This research was conducted at the soybean center in Rantau Rasau District with agroecology peat and tideland. The trial was arranged in a Randomized Block Design (RBD) with ten treatments and four times repeatitions. It consisted of several doses of organic material decanter cake (DC) and the percentage of the recommended amount of mineral fertilizer (RDF). RDF was selected based on Indonesia Food Crop Agriculture Service. Decanter cake from palm oil mill waste was used as a source of organic material. Experimental parameters are plant height, leaf number, grain yield, 100 grain weight, and the number of pods, seeds per pod, and plant. The result indicated the combination of mineral fertilizer and organic material DC had significant differences in increasing plant height and number of leaves. Different types of RDF and DC combinations showed substantial effects on the soybean yield and yield components. The combination of RDF 25% and decanter cake at any dose positively impacted soybean height, leaf number, and grain yield component. The highest dry seed yield of 2.48 tons per hectare was achieved by a combination of 25% RDF and 20 ton ha-1 decanter cake. Soybean yield in this study was higher than Anjasmoro’s description of 2.03–2.25 tons ha-1

This study aims to obtain the best combination of decanter cake (DC) and organic materials,chicken manure (PKA) on soybean growth and yield at Ultisols.. The research design used wasa Randomized Block Design, with treatment of combination of DC and PKA. The treatmentswere control (recommended inorganic fertilizer: 100 kg / ha NPK), DC 15 ton / ha + PKA 0 ton/ha, DC 10 ton / ha + PKA 5 ton / ha, DC 7.5 ton / ha + PKA 7 , 5 ton / ha, DC 5 tos / ha + PKA10 ton / ha, DC 0 ton / ha + PKA 15 ton / ha. Parameters observed: Number of productivebranches, number of pods per plant, number of filled pods, soybean grain yield . The dataobtained were analyzed by means of variance and DMRT at the 5 percent level. The resultsshowed that the combination of DC and PKA could improve soil chemical properties, and hada significant effect on the number of productive branches, yield components and soybean yield.The best combination for the highest soybean yield was the combination of DC 5.0 tonnes / ha+ PKA 10.0 tonnes / ha.

The purpose of this experiment is to evaluate the best combination of inorganic fertilizers and organic material from palm oil mill waste decanter cake, which give the best Chinese kale growth and yield at ex-coal mined soils. This is a pot research, conducted at Agricultural Farm, Agriculture Faculty, Jambi University, using RCBD  with one factors and 11 treatments of combinations of NPK + Decanter Cake fertilizer from palm oil mill solid waste. The parameters observed were increase in plant height and number of leaves, leaf area and plant fresh weight. The results showed, the best treatments for increasing plant height and number of leaves was achieved at 50% of NPK from recommended doses with DC 20 ton/ha or 75% of NPK with DC 20 tons per hectare. For leaf area and plant fresh weight (yield), was achieved at 50 percent of NPK from recommended doses + DC 15 tons per hectare. The conclusion of this research is to increase chienese kale growth and yield in ex-coal mining soil can be done by fertilizing NPK 50 percent from recommended doses + decanter cake 15 tons per hectare.