پديد آورندگان :
محمدوند، الميرا دانشگاه گيلان - دانشكده علوم كشاورزي , كوچكي، عليرضا دانشـگاه فردوسـي مشـهد - گروه اگروتكنولـوژي , نصيري محلاتي، مهدي دانشـگاه فردوسـي مشـهد - گروه اگروتكنولـوژي , يعقوبي، بيژن سازمان تحقيقات آموزش و ترويج كشاورزي - مؤسسه تحقيقات برنج كشور، رشت
كليدواژه :
الگوهاي رويش , تراكم نسبي , رقابت , نسبت كاشت
چكيده فارسي :
زمان رويش و تراكم علف‌هاي هرز اهميت بسياري در اثرات متقابل رقابتي آن‌ها با گياه زراعي دارد. لذا براي علف‌هرز سوروف‌آبي (Echinochloa oryzoides (Ard.) Fritsch)، به‌عنوان يك گونه نسبتاً تازه وارد، بررسي نقش زمان رويش در خزانه برنج (Oryza sativa L.) و در نتيجه سن گياهچه علف‌هرز در هنگام انتقال از خزانه به زمين اصلي و نيز بررسي ميزان اين انتقال و در نتيجه تراكم نسبي علف‌هرز در زمين اصلي ضرورت دارد. نقش سن گياهچه سوروف‌آبي هنگام نشاكاري (10، 20 و 30 روز) و نسبت تراكم سوروف‌آبي: برنج در هركپه (4:0، 3:1، 2:2، 1:3 و 0:4 علف‌هرز: برنج) بر صفات سوروف‌آبي و برنج در هنگام رسيدگي گياه زراعي (90 روز پس از نشاكاري)، طي دو سال مطالعه مزرعه‌اي در قالب طرح بلوك‌هاي كامل تصادفي با سه تكرار مورد بررسي قرار گرفت. افزايش تعداد گياهچه در نسبت‌هاي مختلف كاشت سبب افزايش عملكرد بيولوژيك، عملكرد دانه، عملكرد نسبي هر دو گونه و شاخص غالبيت برنج شد؛ اگرچه شاخص برداشت كاهش يافت. به جز عملكرد دانه برنج در تك‌كشتي و در نسبت 3:1 (علف‌هرز: برنج) سال دوم كه تفاوت معني‌داري با سوروف‌آبي نداشت؛ در ساير نسبت‌ها عملكرد بيولوژيك و عملكرد دانه علف‌هرز بيش‌تر از برنج متناظر بود. شاخص برداشت برنج در همه نسبت‌هاي كاشت بيش‌تر از علف‌هرز بود. در سال اول آزمايش، تيمار گياهچه‌هاي 30 روزه سوروف‌آبي داراي بيش‌ترين عملكرد بيولوژيك، دانه و نسبي علف‌هرز، كم‌ترين عملكرد دانه و نسبي برنج، و كم‌ترين شاخص برداشت هر دو گونه بودند. در همه سنين گياهچه علف‌هرز عملكرد سوروف‌آبي بيش‌تر از برنج متناظر بود. بررسي صفات ارزيابي شده و نمودارهاي سري‌هاي جانشيني حاكي از قابليت رقابت بالاي علف‌هرز نسبت به گياه زراعي بود كه بر ضرورت توجه به گسترش اين علف هرز در منطقه تأكيد دارد.
چكيده لاتين :
Introduction
Weed–crop competition as one of the main reasons for crop loss is often influenced by many factors including
emergence time and density of competing species. Patterns of weed seedling emergence affect the outcome of weed–
crop interference interactions. Information on weed seedling emergence in relation to crop seeding will assist in
developing an optimum weed control program.
Weeds emerge simultaneously with a crop, have the greatest potential impact on crop production. Results from
Chauhan & Johnson (2010) showed the advantage for weeds over rice in situations where these species emerge earlier
in the growing season because of significantly greater biomass production comparing to those emerging later in the
season. Minimal shading and competition for nutrients and soil moisture are associated with early emergence.
The importance of density in competition studies is because of the relationship among plant yield, number of
individuals, and resources present. Increasing the density may enhance the plant’s share of the total resource pool and
reduce resource availability for adjacent plant. Thus, to analyze competition between the crop and weeds, the variation
in density should be considered. Season-long competition with watergrass at densities of 86 and 36 plants/m2 reduced
rice yields by 59% and 46%, respectively.
Understanding relative aggressiveness of component species is required for the integrated weed management and it
would improve weed management strategies. For watergrass as a relatively new-introduced weed species in paddy rice
fields of Guilan province, it is essential to investigate the effects of the emergence time in nursery, to determine weed
seedling ages at the time of transplanting, as well the amount of weed seedling translocation characterizing weed
density in the field.
Materials and Methods
Factorial arrangements of watergrass seedlings ages at the time of transplanting (10, 20 and 30 days), and plant
proportions of weed:rice (0:4, 1:3, 2:2, 3:1, and 4:0) were designed as a randomized complete block with three
replications to study yield characteristics and competitive ability of watergrass and rice over two years of a field
experiment. Individual plants of each hill constituted as a single experimental unit. The area between individual hills
was hand-weeded to avoid competition from other species. At rice maturity stage, plants were harvested, and rice and
watergrass panicles were separated from stems by hand. Panicles were dried to a constant weight at 75 ℃, and weights
were determined. Grain weights standardized to 12% moisture content. Biological yields of rice and watergrass were
also measured after sampling their above-ground parts from an area of 1 m2 and drying at 75 ℃ until constant weight.
Data were subjected to ANOVA, and means were separated using Fisher’s Protected LSD at P < 0.05. Competitiveness
of the species was assessed based on the relative yield (the ratio between the production of the species in the mixture
and in monoculture), relative yield total (total relative yield of the two associated species), aggressivity index and replacement series diagrams (models describing the possible outcomes of the interaction of two species when grown in
a replacement series).
Results and Discussion
For each species, the greater ratio at the planting proportion, the higher biological yield, grain yield, relative yield, and
aggressivity index, but the lower harvest index. When grown in monocultures, and 1 weed: 3 rice of the second year,
the two species produced similar grain yield; however in the other mixtures watergrass produced more biological and
grain yield compared to the rice. Harvest index of rice was greater than watergrass in all planting proportions. In the
first year, trials of 30-day watergrass seedling ages represented the highest values of biological-, grain-, and relative
yield, and the lowest values of grain and relative yield of rice and harvest indices of both species. Also, for all
watergrass seedling ages in both years, weed production was more than rice.
Conclusion
Investigating grain and biological yield, and relative yield of both species, and aggressivity index of rice, beside
replacement series diagrams exhibited higher competitiveness for watergrass comparing to rice. Therefore, it is
important to maintain watergrass control in order to insure the sustainability of transplanted rice production.
