<p style="text-align: justify;">Weed competition becomes a major problem in low land rice. Weeds can reduce rice production up to 60-70%. Mixing herbicides is expected to obtain a broader spectrum of control of the weeds. Inappropriate mixing herbicides may cause antagonism effect which can reduce the effectiveness on the target weed. The objective of the research was to study the antagonism activity of two active ingredients herbicide mixture, cyhalofop-butyl and penoxulam. The treatment was consisted of three types of herbicide with five level of doses, i.e. a single herbicide cyhalofop-butyl (0, 375, 750, 1500, and 3000 g ai ha<sup>-1</sup>), penoxulam (0, 50, 100, 200, and 400 g ai ha<sup>-1</sup>), and the mixture of cyhalofop- butyl 50 g L<sup>-1</sup>+ penoxulam 10 g L<sup>-1</sup>(0, 225, 450, 900, and 1800 g ai ha<sup>-1</sup>). The target weeds were Echinochloa cruss-galliand Monochoria vaginalis. Dry weight of biomass and percent of damage would further determine wheather the herbicide mixture were synergistic, antagonistic, or additive. Since cyhalofop-butyl and penoxulam had a different mode of action, analysis of the data used MSM (Multiplicative Survival Model) method to determine the LD50 of each herbicide treatment and mixture component. The result showed that an active ingredient mixture of cyhalofop-butyl 50 g L<sup>-1</sup>+ penoxulam 10 g L<sup>-1</sup> was not antagonist, with LD50-expectation values of 253.231 g ai ha<sup>-1</sup>and the LD50-treatment of 211.91 g ai ha<sup>-1</sup>. The co-toxicity value was 1.19 (>1).</p><p>Key words: rice field weeds, cyhalofop-butyl, penoxulam, herbicide mixture, MSM (Multiplicative Survival Model), LD50</p>
Two primary compounds from the sesquiterpene group contained in nutsedge's tuber, α-cyperone and nootkatone are related to its benefits as herbal medicine and natural pesticides. This research was conducted to analyze the content of α-cyperone and nootkatone at three different part of the tuber (whole-tuber, peeled-tuber, and tuber's peel) so that it indicates the level of activity from these parts of nutsedge tuber in the tropics. The ethanolic extracts were analyzed using high-performance liquid chromatography (HPLC) equipped with C18 column, acetonitrile and aquabidestillata (65:35) as a mobile phase and PDA detection at 254 nm. The analysis showed the results that the highest content of α-cyperone was on the whole-tuber 1.074%, followed by peeled-tuber 0.736% and tuber's peel 0.202%. Nootkatone was not found in this nutsedge's tuber.
Extreme weather incidents refer to high rainfall and strong winds have been speculated to be detrimental on rice production. However, researches on the local adaptation to their impact on rice production are limited especially on tropical region like Indonesia. A study was conducted in Pesawaran, West Lampung, North Lampung, and Bandar Lampung using time series data of 2000-2015 and ground checking during extreme weather and normal seasons and its implication on sustainable management. Data were evaluated using multivariate regressions. Results demonstrated that the impact of extreme weather on the reduction of rice production was weak, 0.92%. Shifting on rice production among swampy, irrigated, and dry lands at which covered area of 13.67%, 42.69% and 43.65%, respectively, minimized the impact of the extreme weather. During limited precipitation, irrigated and swamplands had 2.5-3.0 times cropping intensity. Conversely, during La-Nina with excess precipitation, cropping in irrigated and drylands increased by 20 and 58%, respectively. Moreover, the local government maintained annual production improvement by about 5% through expansion of irrigated land, high yielding varieties and inputs subsidies. Considering that incident of extreme weathers tended to occur more frequently, consequently, planting calender utilization and rice variety adapted should be implemented.
The research objective is to determine the dosage and frequency of given of P fertilizer on soybean varieties in soil mineral and peaty mineral under saturated soil culture in tidal land. The research was conducted in mineral and peaty mineral soil of tidal area type B and C in District of Tanjung Lago, Banyuasin Regency, Province of South Sumatra from April to August 2014. This study used split plots. Willis and Tanggamus varieties was main plot, application time (0, 0 and 4 MST) was on sub plot, and fertilizer dose (0, 36, 72, 108 kg P 2 O 5 ha -1 ) was on sub-sub plot. Experiments results showed that soybean productivity in peaty mineral soil was lower than mineral soil. In peaty mineral soil, application time of phosphorus at 0 and 4 MST was able to increase growth and productivity of soybean, while phosphorus application time on mineral soils was better at 0 and 4 MST of planting time on mineral soils. Dose of 108 kg P 2 O 5 ha -1 increased the productivity of soybean in peaty mineral soils, while dose of 72 kg P 2 O 5 ha -1 was better in mineral soil. In peaty mineral soil, interaction (Tanggamus, application at 0 and 4 MST as well as 72 kg P 2 O 5 ha -1 ), showed the highest productivity of soybean (2.83 ton ha -1 ). Meanwhile interaction (Tanggamus, application at 0 and 4 MST as well as 72 kg P 2 O 5 ha -1 ) showed the highest productivity of soybean (3.8 ton ha -1 ), respectively in mineral soil under saturated soil culture techniques in tidal land. ABSTRAKTujuan penelitian adalah menentukan dosis dan pemberian pupuk P pada varietas kedelai di tanah bergambut dan mineral dengan budidaya jenuh air di lahan pasang surut. Penelitian ini dilaksanakan di tanah bergambut dan mineral lahan pasang surut tipe B dan C di Kecamatan Tanjung Lago Kabupaten Banyuasin Provinsi Sumatera Selatan dari April hingga Agustus 2014. Penelitian menggunakan rancangan petak-petak terpisah. Petak utama adalah varietas (Willis dan Tanggamus), anak petak adalah waktu aplikasi (0, 0 dan 4 MST), dan anak-anak petak adalah dosis pupuk (0, 36, 72, 108 kg P 2 O 5 ha -1 ). Hasil percobaan menunjukkan bahwa produktivitas kedelai di tanah mineral bergambut lebih rendah daripada di tanah mineral. Di tanah mineral bergambut waktu aplikasi fosfor pada 0 dan 4 MST lebih meningkatkan pertumbuhan dan produktivitas, sedangkan waktu aplikasi fosfor di tanah mineral lebih baik pada umur pada 0 dan 4 MST. Dosis pupuk 108 kg P 2 O 5 ha -1 meningkatkan produktivitas tanaman kedelai di tanah mineral bergambut sedangkan dosis 72 kg P 2 O 5 ha -1 lebih baik untuk tanah mineral. Pada tanah mineral bergambut, interaksi (Tanggamus, waktu aplikasi 0 dan 4 MST serta dosis 72 kg P 2 O 5 ha -1 ), menghasilkan produktivitas tanaman kedelai tertinggi (2.83 ton ha -1 ). Sementara itu interaksi (Tanggamus, waktu aplikasi 0 dan 4 MST serta dosis 72 kg P 2 O 5 ha -1 ) menghasilkan produktivitas tanaman kedelai tertinggi 3.8 ton ha -1 di tanah mineral dengan teknik budidaya jenuh air di lahan pasang surut.Kata kunci : Dosis pupuk, Glycine max (L) Merr., fosfor, kemasa...
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