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.

The purpose of this research was to gain a technological breakthrough in controlling Fe toxicity (Fe2+) on Ultisol in a new established rice field by using humic acid from rice straw compost and water management, so that optimal production of rice plants could be achieved. The experiment was designed using a 2 &times; 4 factorials with 3 replications in a split plot design. The main plot was water management consists of 2 levels: continuous and intermittent irrigation (2 weeks flooded and 2 weeks field capacity). Small plot was humic acid which was extracted from rice straw compost by NaOH 0.5 N which consists of 4 levels: 0, 200, 400, and 600 mg kg-1.&nbsp; The results showed that applications of humic acid from 0 to 600 mg kg-1 that was followed by 2 weeks of intermittent irrigation decreased Fe2+ concentration. It was approaching levels that were not toxic to plants, with soil Fe2+ between 180-250 mg kg-1. The best treatment was found at the application of 600 mg kg-1 humic acid extracted from rice straw compost combined with 2 week flooded &ndash; 2 weeks field capacity of water management. Those treatment decreased Fe2+ concentration from 1,614 to 180 mg kg-1 and increased the dry weight of grain from 5.15 to 16.73 g pot-1 compared to continuous flooding and without humic acid application.<p>[<strong>How to Cite</strong>: Herviyanti, TB Prasetyo, F Ahmad and A Saidi. 2012. Humic Acid and Water Management to Decrease Ferro (Fe2+) Solution and Increase Productivity of Established New Rice Field. J Trop Soils 17 (1) : 9-17. doi: 10.5400/jts.2012.17.1.9]</p><p>&nbsp;</p><p>[<strong>Permalink/DOI: </strong><a href="http://dx.doi.org/10.5400/jts.2012.17.1.9" target="_blank">www.dx.doi.org/10.5400/jts.2012.17.1.9</a>]</p><p>&nbsp;</p>

The pressure of population growth and the economy has an impact on changes in land use in Sub-watershed Sumpur Singkarak West Sumatra, Indonesia. Changes in land use are analyzed spatially and temporally using satellite imagery Landsat TM 7 and 8 (resolution 30 m) that has been in the interpretation of 2004 to 2014. The analysis is done by comparing the changes in land use in the area of forest, farming and settlement. From the analysis it can be concluded that there has been a decline in forest area of 128 ha (1.6%), an increase in mixed-farming area of 146 ha (16.1%), an increase in settlement area of 143 ha (26%) for 11 years in Subwatershed. In 2011, a change of 3125 ha of rice-paddy which have been changed become dry land an area of 2645 ha. This is due to the farming community, prefer to plant horticulture and crop plant from the rice plant.In the protected forest area has been used for settlement area of 1.37 ha and for dry land area of 11.41 ha. In the tourist nature reserve forest areas have been used for rice paddy area of 0:33 ha and for dry land area of 42.91 ha.

A research aiming to improve soil aggregate stability of Ultisol in terms of creating sustainable agriculture and environmental development was conducted by applying fresh organic matter (OM)  into soil.  Three types of  OM sources used were Titonia diversifolia, Chromolaena odorata, dan Gliricidia sepium.   This research was conducted in Ultisol Limau Manis Sumbar having annual rainfall > 5000 mm, in 2008.   The fresh OM used was cut, mixed with soil up to 20 cm depth, and then incubated for approximately one month before corn seeds were planted.  Soil was sampled before being treated with OM and then after harvesting corn (4 moths after applying OM).  Soil OM content as well as soil aggregate stability (AS) and several other soil physical properties wer analysed in laboratory.  The results showed that soil OM content and AS increased after one planting period.  Besides that, soil physical properties were also improved.  As soil physical properties became better, corn production was also higher at plot with than without OM application.  Among 3 species of OM added, Tithonia diversifolia gave highest corn biomass.  Level of land slope (0-8% dan 15-30%) did not show significant difference either for biomass or for soil OM content and soil AS.Key Words: marginal soil, green manure, soil aggregate stability, soil organic matter

A research about relationship between soil properties and crop yield was conducted in Pandai Sikek, Tanah Datar Region, center for cabbage and carrot production, West Sumatra in 2004 and 2005. Soil samples were collected from rainfed paddy soils by purposive random sampling. Soil samples were analyzed in Soil Laboratory, Agriculture Faculty and Agriculture Polytechnique Laboratory, Andalas University. Several soil physical properties analysed were soil bulk density and total soil pores by using gravimetric method, permeability with de Boodt method, soil water content at several pF values using pressure plate apparatus, and soil strength by using penetrometer. Soil chemical parameters analysed were soil pH using pH-meter, organic-C using Walkley and Black, available P using Bray II, and cation exchange capacity using NH4-leaching at pH 7.0, and N-total using Kjehdhal method. Crop productions were sampled from a 3x3 m 2 of soil sampling area. The result showed that soils planted by cabbage and carrot had good soil physical properties, such as having balanced pore size distribution. The chemical properties of the soils were good as well, except N, K-and Ca-exchangeable which were very low. The other soil properties were quite good. Soil physical properties gave different response on both crops. Carrots were more response aeration pore and soil organic matter content, then cabbage was more response on BV, TSP, and slow drainage pores. While soil chemical properties did not give significant response. Both crops responded on Ca, but cabbage was more response on N-total, and carrot on CEC and saturated cation