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Four detergents were tested as selective C sources for the plant growth-promoting rhizobacteria Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens ANP15. CO-720 (Igepal CO-720) or DOS (dioctyl sulfosuccinate), applied at 0.2% to the soil, increased the number of detergent-adapted, inoculated strains by almost 1.5 log units after 25 days, accounting for virtually the entire increase in total bacteria. The same dose of Tween 80 or N-laurylsarcosine, on the other hand, increased the indigenous populations by almost 2.5 log units, with only minor increases in the number of detergent-adapted inoculated strains. When CO-720 or DOS was initially supplied, the number of detergent-adapted 7NSK2 organisms was about 2 log units higher after 3 months of incubation than for the detergent-unadapted strain. This better survival resulted in a significantly higher root colonization of maize in a pot experiment with soil inoculation, with a significantly (P < 0.05) higher shoot dry weight (18 to 33%). In a first field experiment with rhizosphere inoculation of 1-month-old maize plants, no effects on the height of two maize cultivars could be observed 1 month after inoculation. In a second field experiment, leaf and stem dry weights of yellow mustard and grass dry weight were increased in the treatments with seed and soil inoculation of the detergent-adapted 7NSK2 in combination with CO-720 application by, respectively, 7 to 8%, 19 to 23%, and 20 to 31%, although only the increases in grass dry weight were statistically significant at P < 0.1. To some extent, 7NSK2 and DOS application also positively affected the mineral content of yellow mustard.

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Ubi kayu merupakan tanaman pangan yang banyak dibudidayakan di Provinsi Lampung. Mayoritas petani ubi kayu menerapkan sistem olah tanah intensif beserta aplikasi herbisida kimia dengan anggapan lebih efisien waktu, tenaga, dan biaya namun melupakan dampak negatifnya terhadap kesuburan lahan Penelitian ini bertujuan untuk mengetahui pengaruh sistem olah tanah dan aplikasi herbisida terhadap populasi dan biomassa cacing tanah pada pertanaman ubi kayu (Manihot utilissima) diLahan Lapangan Terpadu Fakultas Pertanian, Universitas Lampung. Percobaan dirancang menggunakan RAK dengan dua faktor yaitu sistem olah tanah (T) dan aplikasi herbisida (H). Sistem olah tanah terdiri dari olah tanah intensif (T 1 ) dan olah tanah minimum (T 2 ), sedangkan aplikasi herbisida terdiri dari tanpa aplikasi herbisida (H 0 ) dan aplikasi herbisida (H 1 ). Herbisida yang digunakan yaitu herbisida berbahan aktif isopropilamina glifosat + isopropilamina 2,4 D dengan dosis yang digunakan yaitu 160 ml/1 tangki (1 tangki=16 liter air). Data yang diperoleh diuji dengan analisis ragam dan dilanjutkan dengan uji BNT.Hasil penelitian menunjukkan bahwa sistem olah tanah tidak berpengaruh terhadap populasi dan biomassa cacing tanah, namun perlakuan herbisida berpengaruh terhadap populasi cacing tanah pada pengamatan 0 BST (sebelum tanam), dan uji BNT menunjukkan bahwa populasi cacing tanah lebih tinggi pada lahan yang tidak diaplikasikan herbisida. Populasi danbiomassa cacing tanah ditemukan lebih tinggi pada lapisan tanah 0 – 10 cm dan identifikasi cacing tanah di laboratorium menunjukkan bahwa cacing tanah yang ditemukan yaitu dari famili Megascolecidae genus Pheretima. Uji korelasi menunjukkan bahwa kadar air tanah berpengaruh terhadap populasi maupun biomassa cacing tanah.

Two protocols for following soil methane enrichment were used, one with methane dosed as a carbon source ([C]-soil) and one with methane plus minerals ([C+M]-soil). Methane oxidation occurred much faster in soil receiving minerals in addition to methane than in the control soil receiving only methane. In both treatments, only a small fraction of methane (2% to 14%) was converted into microbial biomass C. Nevertheless, a strong increase in soil microbial biomass (up to 1.5 to 2.0-fold) was achieved in the [C+M]-soil in a 3-week period. Due to methane application, the NO3 (-) content of the soil was significantly decreased, by 83% to 90% in the [C]-soil and by 56% to 83% in the [C+M]-soil. Soil enzymatic activities were slightly increased in the [C+M]-soil only. The soil-methane incubation did not alter the composition of the monitored microbial populations in the soil or in rhizosphere of plants. In the [C]-soil, methane incubation resulted in reduction of the shoot dry wt of maize by 8% to 12%. In the [C+M]-soil under non-limiting mineral-nutrient status, a significant increase in shoot dry wt was observed for maize (13%), a neutral effect was registered for spinach and a negative effect was observed for wheat.