The main problem of the use of N fertilizer in paddy soil Vertisols is the low efficiency. Ureahumic acid applications at certain dosage are believed to increase rice growth and production. This study was aimed to examine the effect of urea and urea-humic acid to the amount and form of N-available, N uptake, plant growth, and the production of rice. Five dosage levels of urea-humic acid were applied for rice on Vertisols. Results of the research showed that the urea-humic acid fertilizer could increase the content of N-NH4 + soil at 28 days and N-NO3 -soil at 42 days. The urea-humic acid could improve plant height, number of tillers, and total dry weight. The highest rice production is achieved by 100% humic acid-urea, especially on parameters of dry weight effectively harvested and effectively milled, with 5.56 tons and 4.61 tons per hectare respectively. Correlation between soil N-NO3 -level with soil N-NH4 + level was significant at p = 0.05 (r = 0.871). Efficiency of urea-humic acid fertilizer at 100% recommended dosage (200 kg urea-humic acid) to the dry weight of effectively harvested crop with dry weight of effectively milled crop was 22% compared to the recommended urea fertilizer (200 kg ha -1 ).

Rice husk biochar and compost application are expected to improve soil chemical properties such as pH, organic carbon, and available P in Ultisol, which in turn improves crop growth and P uptake by plants. The purpose of this research was to analyze the effect of the combination of rice husk biochar and compost on the soil chemical properties (pH, organic carbon, and available P), maize growth, and P uptake by maize in an Ultisol. The research used a Randomized Block Design with six treatments (P0: control; P1: 4 t biochar ha-1; P2: 30 t compost ha-1; P3: 4 t biochar ha-1 and 30 t compost ha-1; P4: 8 t biochar ha-1 and 30 t compost ha-1; P5: 4 t biochar ha-1 and 60 t compost ha-1) and four replications. The result showed that the combination of 8 t rice husk biochar ha-1 and 30 t compost ha-1 showed a significant effect on increasing pH, organic carbon, and available P in an Ultisol, increasing the height of maize crops at 4 and 6 WAP (weeks after planting). However, it had no effect on the number of leaves and showed an effect on the increase in P uptake of maize crop.

Soil moisture stress in coffee plant impacts on the productivity of coffee fruit at PT.Perkebunan Nusantara XII, it is because the low ability of the soil to store water. The ability of the soil to store water can be increased by increasing the organic matter content of soil, especially humic substances. Soil organic matter plays an important role in the improvement of soil physical properties, especially the availability of soil moisture for plants. The purpose of this study was to analyze several humification parameters at four age of plantations plots of coffee and its relation to the water distribution potensial on Inceptisol PT. Perkebunan Nusantara XII Malang district. The research was conducted at PT. Perkebunan Nusantara XII were taken soil samples from 8, 28, 40, and 80 years old robusta coffee plots at 0-30 cm and 30-60 cm soil depth. The results showed that the increasing the age of the coffee plantations significantly increased the input of organic matter in the soil, with indicators of increased litter on soil surface, increased levels of soil C-organic and N-total, humic acid and soil pH. Increasing age of coffee plantations until 80 years did not affect to the value of humification parameters (C/N ratio, HA/FA ratio, E4/E6 ratio, and the humification rate (HR)). The age of coffee plantations affected the total acidity, carboxylic groups and phenolic OH, where the values tended to decrease with the older of coffee plantations in the 0-30 cm of soil layers and increased in 30-60 cm. Increasing age of coffee plantations improved the total pores and available water content in the 0-30 cm of soil layer.

The Inceptisol of Karangploso has low soil pH, low organic matter (OM), medium total soil N, very low C/N ratio, and low available sulphurthat cause low soil productivity. The application of bokashi preserves strongly productivity and organic matter in the soil. This research aimed to determine the effect of bokashi application in improving soil chemical properties and N, P, Savailable in an Inceptisol of Karangploso. The experiment was conducted in greenhouse of Facultyof Agriculture, Brawijaya University using a completely randomized design with 7 treatments and 3 replications. The treatments consisted of O1 = dose of 5 t ha -1 + ½ A, O2 = dose of 10 t ha -1 + ½ A, O3 = dose of 15 t ha -1 + ½ A, O4 = dose of 20 t ha -1 + ½ A, O5 = dose of 25 t ha -1 + ½ A, and O6 = dose of 30 t ha -1 + ½ A. The results showed that the increasing dose of bokashi significantly increased soil pH (from 5.1 to 5.4), C/N ratio (from 9.64 to 9.93), P-available (from 141 to 142.6 ppm P) at 60 DAI (days after incubation), total N (from 0.21 to 0.24% at 30 DAI and 0.18% to 0.24% at 60 DAI ) and NO3 -(from 24.96 to 65.47 ppm at 30 DAI and 14.91 ppm to 39.20 ppm at 60 DAI) compared to the control, but it had no significantly effect on organic carbon, OM, SO4 2-in soil. The correlation test showed that there was a strong and positive correlation between pH and NO3 -(r=0,77*), organic carbon and NO3 -(r=0,63), organic carbon and P-available (r=0,78*), OM to NO3 -(r=0,70*), and OM to P-available (r=0,86*).

Application of spent coffee ground compost is expected to improve soil chemical properties of Andisol Ngabab which has low C-organic and N contents, very low P content, and moderate content of Na content. The purpose of this study was to explore the effect of application of Robusta spent coffee grounds compost application on soil chemical properties of an Andisol. This study used a completely randomized design with five treatments and three replications. The treatments tested were P0 (control, without application of spent coffee ground compost), P1 (50% dose of spent coffee ground compost aplication = 10 t ha-1), P2 (100% dose of spent coffee ground compost application = 20 t ha-1), P3 (150% dose of spent coffee ground compost application = 30 t ha-1), and P4 (200% dose of spent coffee ground compost application = 40 t ha-1). The results of this study showed that the application of spent coffee ground compost with a dose of 150%= 30 t ha-1 (P3) and dose of 200%= 40 t ha-1 (P4) on an Andisol of Ngabab significantly increased pH, organic-C, total-N, available-P, exchangeable-K (in 2, 6 and 8 weeks), exchangeable-Na, and CEC (in 4, 6 and 8 weeks) compared to control treatment or without application of spent coffee ground compost (P0).