ArticlePDF AvailableAbstract and Figuresp>Abstrak. Penggenangan terus-menerus di lahan sawah akan berpengaruh terhadap keseimbangan kimia dan biologi tanah. Pergantian aerobik dan anaerobik di lahan sawah merupakan satu kontrol alami yang efektif mengendalikan keseimbangan biologi dan nonbiologi sehingga tanah sawah menjadi sehat dan tetap produktif. Penerapan rotasi tanamanantara tanaman padi dengan palawija maupun hortiklutura merupakan salah alternatif yang bijak untuk tetap mempertahankan produktivitas dan kesuburan lahan, dan perekonomian petani. Penerapan rotasi tanam memiliki peranan terhadap beberapa aspek antara lain agronomi, ekonomi dan lingkungan. Pengelolaan lahan pertanian tanah sawah secara terus-menerus pada berbagai rotasi tanam dapat meningkatkan berat jenis tanah, dan persentase fraksi lempung dalam tanah sawah. Rotasi tanaman padi-palawija/hortikultura dapat memperbaiki srtuktur tanah melalui peningkatan nilai MWD. Penerapan rotasi tanaman secara terus-menerus berpengaruh nyata terhadap perubahan sifat kimia tanah seperti pH, N-total, P dan K-tersedia, KPK tanah, dan C-organik. Penerapan rotasi tanaman padi-jagung pada 1 – 2 tahun pertama memberikan kadar N-total tanah, NO3- dan DOC yang sangat tinggi. Penanaman jagung di musim kemarau pada rotasi tanaman padi-jagung dapat menyimpan air dan menekan pencucian hara, daripada penanaman padi-padi dalam jangka panjang. Pengembalian nutrisi nitrogen dalam rotasi tanaman dapat dilakukan melalui penanaman tanaman legum setelah penanaman tumbuhan serealia dan sejenisnya. Abstract. Continuous flooding in paddy fields will disrupt the biological and chemical balance of the soil. Substitution of aerobics and anaerobics in paddy fields is a natural control that effectively controls the biological and nonbiological balance so that the paddy fields become healthy and remain productive. Application of plant rotation between rice plants with crops and horticulture is a wise alternative to maintain the productivity and fertility of paddy field, and the economy of farmer. Application of rotation has a role to play on several aspects such as agronomy, economy and environment. Continuous management of paddy field on various rotations of cropping can increase bulk density, and the percentage of clay fraction in paddy soil. Rotation of rice-upland/horticulture can improve soil structure by increasing the value of MWD. Continuous application of crop rotation has a significant effect on changes in soil chemical properties such as pH, totalN, available P and K, CEC, and organic carbon. The application of rotation of rice-maize in the 1–2 years can give very high total N, NO3- and DOC levels. The planting of maize in the dry season on a rotation of rice-maize can store water and suppress nutrient leaching, rather than long-term rice-rice cultivation. Return of nitrogen nutrients in crop rotation can be done through planting legumes after planting cereals and the pori makro berkurang sampai 87%, pori berukuran 0,6 – 30 μm pori kapiler dan pori berukuran Abstrak. Lahan pertanian eksisting penghasil bahan pangan terutama sawah dan lahan kering menjadi tumpuan harapan untuk memenuhi kebutuhan pangan 258,7 juta jiwa penduduk pada tahun 2017. Usaha pencapaian swasembada berkelanjutan dihadapkan pada i peningkatan jumlah penduduk sekitar 3,4 juta jiwa setiap tahun, ii konversi lahan sawah ke non pertanian dengan laju sekitar ha tahun-1, sementara laju perluasan lahan sawah hanya sekitar ha tahun-1, dan iii perubahan iklim global yang menyebabkan peningkatan intensitas dan frekuensi kejadian iklim ekstrim berupa kekeringan, kebanjiran, longsor, yang selanjutnya meningkatkan intensitas serangan hama/penyakit tanaman. Upaya dan strategi untuk mengatasi permasalahan tersebut diantaranya melalui, pertama, intensifikasi dengan inovasi teknologi pada 4 juta ha sawah irigasi teknis, 4,1 juta ha lahan sawah sub-optimal tadah hujan, irigasi sederhana, sawah rawa melalui perbaikan saluran irigasi dan sistem drainase, pemupukan berimbang, pengembangan varietas unggul, dan peningkatan Indeks Panen dari 1 menjadi 1,5. Kedua, pengendalian konversi lahan melalui kesepakatan berbagai pemangku kepentingan, kerjasama lintas kementerian/ lembaga serta antara pemerintah dengan swasta dan masyarakat untuk meningkatkan kesadaran akan bahaya konversi lahan terhadap ketahanan pangan, kestabilan sosial, ekonomi dan politik. Ketiga,perluasan areal tanam di lahan perkebunan kelapa sawit muda 5,1 juta ha dan karet 0,54 juta ha, serta pada perkebunan kelapa 2,15 juta ha. Tersedia varietas toleran naungan untuk padi gogo, jagung dan kedelai untuk mendukung usaha ini. Keempat, perluasan areal pertanian baru untuk tanaman pangan pada lahan potensial di lahan rawa pasang surut, lebak, dan gambut dan pada lahan basah non rawa untuk sawah irigasi dan tadah hujan, serta di lahan kering dengan lereng Table 4. Furthermore, the soil particle-size distribution did not differ among any treatment combinations when measured in 2010 P > Table 4. Analysis of variance summary of the inherent differences of soil properties before tillage, fertility and crop rotation treatments. Soil properties and their interactions related to the inherent soil differences in the assigned treatment combinations on soil bulk density BD, soil organic carbon SOC content, total nitrogen TN content, portion of SOC in soil organic matter SOM, portion of TN in SOM, and carbon to nitrogen ratios CN prior to any treatment being imposed in 1999. The study site was located at the Rice Research and Extension Center near Stuttgart, AR on a silt-loam soil. Treatment effects in bold are considered non-significant P > As hypothesized, SOC P < and TN P = contents kg m⁻² in the top 10 cm were affected by crop rotation and time, when averaged across tillage treatments and fertility regimes Table 5. The SOC content in rotations that included winter wheat [ RW and RWSW] increased more than 30% for a sequestration rate of kg⁻¹ SOC m⁻² yr⁻¹ and the continuous rotation increased 16% for a sequestration rate of kg⁻¹ SOC m⁻² yr⁻¹ from 1999 to 2010, whereas SOC contents in the RS, RC, and RCS rotations did not differ over the 11-year time period Figure 1A. Likewise, TN contents increased 36 to 46% in the RW rotation for a sequestration rate of kg⁻¹ TN m⁻² yr⁻¹ and in the RWSW rotation for a sequestration rate of kg⁻¹ TN m⁻² yr⁻¹ Figure 1B. However, the RS rotation increased 19% for a sequestration rate of kg⁻¹ TN m⁻² yr⁻¹ from 1999 to 2010, whereas the TN contents in R, RC, and RCS rotations did not differ over time Figure 1B. The greater increase of SOC and TN over time in rotations with wheat could be partially due to greater quantities of annual biomass from the double-cropped rotations, as opposed to rotations that were fallow in the winter, and partially due to the presence of wheat in the ground during sampling. The presence of the wheat crop suggests there were greater concentrations of fresh root biomass and increased microbial activity in the near-surface soil compared to rotations that were fallow during the study focuses on the effects of long-term rice rotated with milk vetch being as green manure on the composition of bacteria in rice roots. The endophytic bacterial communities in rice roots of the rice-rice-milk vetch R-R-MV and the rice-rice-winter fallow R-R-WF crop rotations with a 28-year research history were investigated using combined culture-dependent and culture-independent methods. It was found that the endophytic bacterial population in rice roots with the green manure was significantly higher than that of without it. There were 169 and 77 strains of endophytic bacteria that were isolated from rice roots of the R-R-MV and the R-R-WF, respectively. The 16S rRNA gene analysis shows that the 77 R-R-WF bacteria belong to 15 species of 14 genera while the other 169 R-R-MV bacteria belong to 21 species of 19 genera, in which Herbaspirillum and Cedecea were two mutually dominant populations and Burkholderia, Pseudomonas, Sphingomonas, and Pantoea accounted for large proportions of the endophytic bacteria in rice roots through R-R-MV rotation. The analysis of 16S rDNA clone libraries showed that the Shannon-Weaver diversity index of endophytic bacteria in R-R-MV approximates that in R-R-WF rotation, whereas the richness indexes of Chao 1 and ACE in R-R-MV rotation system were significantly higher than those in R-R-WF rotation. The diversity of endophytic bacteria was richer in R-R-MV. Both the culture-dependent and the culture-independent method revealed significant effect of long-term different tillage systems on the microbial community. C. A. CampbellR. P. ZentnerSoil organic matter was monitored in a 24-yr crop rotation experiment conducted on a medium-textured Aridic Haploboroll in southwestern Saskatchewan. Prior to the study, the land had been in a spring wheat fallow rotation for ~50 yr. Only the 0- to segment showed significant treatment effects. Due to good weather and crop yields in the first 15 yr, soil organic matter had increased under well-fertilized annually cropped rotations. Because of several dry years in the final 9 yr, all rotations except a well-fertilized, fallow-winter cereal-wheat system lost organic matter. The fallow-flax-wheat rotation receiving N and P fertilizer had the lowest soil organic matter. Soil organic matter in the well-fertilized fallow-winter cereal-wheat rotation remained constant. -from Authors