Abstr actThe purpose of this research is to study interaction of humic substances extracted from subbituminus coal with P fertilizer on the chemical properties of Ultisol and crop production of corn (Zea mays L.). The experiment was designed in completely randomized design having 2 factors (4 x 4) with 3 replications. The first factor was dose of humic substances (A) which consists of 4 levels (A1 = 0 ppm, A2 = 400 ppm, A3 = 800 ppm, and A4 = 1200 ppm). The second factor was level of fertilizer P (B) (B1 = 100% recommendation, B2 = 75% recommendation, B3 = 50% recommendation, and B4 = 25%). The result showed that : 1) There is no interaction between humic substances and P fertilizer on the chemical nature of Ultisol and crop production of corn (Zea mays L.) 2) Use of humic substance for 800 ppm with some level of P fertilizer could improve some chemical properties of Ultisol such as decreased in content of Al-exch by 0,38 me/100 g soil, increased in P-available by 22,16 ppm, CEC by 8,42 me/100 g soil and P nutrient by 0,10 %, as well as corn yield by 25,67 g/pot compared to soil without humic substances 3) The use of SP-36 for 50 % with some level of humic substances increased in plant height by 26,58 cm, P nutrient by 0,11 %, and the use of 75 % SP-36 increased corn yield by 5,84 g/pot compared to 25% of P recommended.

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A research was carried out at glass house and at Soil Laboratory of Faculty of Agriculture, Andalas University Padang. The experiment was aimed to determine the interaction between humic material from compost and P fertilizer on some chemical properties of Oxisol, nutrient uptake and corn production. This experiment consisted of 2 factors (4 x 4) with three replications which were allocated in completely randomized design (CRD). The first factor was humic material having 4 doses (0, 400, 800, and 1200 ppm) and the 2nd factor was P fertilizer having 4 doses (100%, 75%, 50%, and 25% of recomendation (R)). The result showed that there was : 1) Interaction between humic materials and P fertilizer for the quality the corn seeds. Application of 800 ppm humic material improved the quality of the seeds even though at low level of P fertilizer. 2) Then, it also increased availability of P by 23.03 ppm, N total by 0.09 %, and decreased Al-exch by 0.53 me (100 g) -1 and Fe-exch by 25.62 ppm compared to threatment without application of humic material. Likewise, nutrients (N and P) uptake by plant also increased by 0.28 and 0.03 %, respectively. 3) Application of P fertilizer at 75 % R increased soil P availability by 3.77 ppm, N and P content of plant by 0.43 % and 0.06 %, and seed weight by 13.20 g and decreased Fe-exch by 21.16 ppm, compared to 25 % R of P fertilizer.

This research was conducted in soil chemical laboratory, Faculty of Agriculture, Andalas University, Indonesia from December 2016 until May 2017. The purpose of this research is to determine the level of activeness of powder of Sub-bituminous coal with Sodium Hydroxide (NaOH) and to determine the appropriate dosage of the mixture in improving the chemical properties of Ultisols. This research was conducted in 2 stages: first stage study with 10 treatments (1% to 10% (w/w) NaOH) and the second stage study on soil using 15 treatment combinations (3 doses of powder Sub-bituminous coal with 5 doses of NaOH). The results of the first stage of research are the addition of NaOH in Sub-bituminous could increase the activity of powder Sub-bituminous coal with parameters of pH, CEC, and increases the number of O-H, C=O, and CH 3 groups. The results of stage II study is the provision of a mixture of 20 ton.ha -1 of Sub-bituminous coal powder and 10% of NaOH were able to increases the pH of H 2 O, CEC, organic-C, Available-P, and Total-N Ultisol each of 1.49 units, 28.08 me.100g -1 , 1.63 % C, 2.37 ppm P, 0.06% N, and decreases Al-exch Ultisol by 1.17 me.100g -1 and , SAR Ultisol by 0.03, and ESP Ultisols by 0.82 % compared to natural soil.

Saat ini mulai berkembang pemanfaatan limbah organik pertanian untuk dijadikan biochar sebagai bahan pembenah tanah alternatif dan upaya mengurangi dampak negatif limbah atau sampah di lingkungan. Tujuan penelitian ini adalah untuk mendapatkan dosis biochar terbaik dalam memperbaiki beberapa sifat kimia tanah Inceptisol. Penelitian ini menggunakan Rancangan Acak Lengkap dengan 5 perlakuan dan 3 ulangan yaitu: A = 0 t/ha (0,00 g/500 g tanah), B = 5 t/ha (1,25 g/500 g tanah), C = 10 t/ha (2,50 g/500 g tanah), D = 15 t/ha (3,75 g/500 g tanah), dan E = 20 t/ha (5,00 g/500 g tanah). Hasil penelitian menunjukkan bahwa dosis 20 t/ha biochar kulit buah pinang berpengaruh sangat nyata terhadap peningkatan pH, C Organik, P- tersedia, KTK, N- total, K-dd, Ca-dd dan Mg-dd yaitu masing-masing sebesar 0,14 unit, 0,93%, 18,87 ppm, 21,32 cmol(+)/kg, 0,2%, 0,66 cmol(+)/kg, 1,17 cmol(+)/kg, dan 1,91 cmol(+)/kg dibandingkan dengan kontrol.

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A reseach about determination land degradation on several plantation ecosystems in Dharmasraya Regency, West Sumatra. This research was aimed to study types of perennial crops (trees) which contributes to alleviate land degradation. The work was conducted in Sungai Rumbai Dystrict, Dharmasraya regency and in Soil Science Laboratory, Agriculture Faculty Andalas University. Soil samplings were taken at Ultisols having 0-8% slope (flateundulating). Land use type being considered was original forest, oil palm, rubber, coffee, and cocoa plantation. Composite soil samples were taken for four replications on 1-20 cm depth. At each sampling site was accompanied by five drilling soils. Then, four undisturbed soil was also sampled at the same depth with disturbed soil samples for determining soil bulk density values. The data collected were analyzed statistically by using analyses of variance, and then continued by using Least Significant Difference (LSD) at 5% level. The result showed that rubber and cacao plantation contributed to better soil ecology value than oil palm and coffee land use. It could be proved from organic carbon (OC) and bulk density (BV) of the soils which were alsmost the same as those from forest land use.

The research about residue effect of humic acid from imperata compost and water management to decrease the dissolved of iron (fe) on recently used ricefield had been conducted from march till august 2007.  The objective is to study residue effect of humic acidity aplication and water management to controlling Fe and to increase rice production on recently used ricefield.  The experiment using design factorial 2 x 4 with three replication wich is place as the split plot.  The major factor is water management consisted of two treatment, thos were continously flooded (P1) and flooded and dried (intermittence) with two week interval (P2). The minor factor are four level from residue effect of humic acid  (0, 200, 400, 600 ppm).  The result of this study can provided the information that residue effect of humic acid at 600 ppm can reduce solubility of Fe2+ from 327,91 to 37,53 ppm for continously flooded and from 173,51 to 38,13 ppm for intermitten flooded. And the yield of rice (dry weight of 1000 grain ad straw) increase as much as 4,9 and 5,38 g with residue effect of humic acid at 600 ppm combination with intermittence flooded.Key word : humic acid, iron, recently used ricefield, intermittence, flooded.