Impact of Hydrogel Polymer on Water Productivity, Weed Control Efficiency and Yield of Broadcast-Seeded Rice

A field study was investigated at the Experimental Farm of Rice Research Department, Sakha Agricultural Research Station, Kafrelsheikh, Egypt during summer seasons of 2020 and 2021 to study the capability of hydrogel polymer application under different irrigation intervals and chemical weed control on water conservation and weed control under Egyptian broadcast-seeded rice (Giza 179 cv). A strip spit design with three replicates was used during the study. Three irrigation intervals (irrigation every 5 days (I1), 10 days (I2) and every 15 days (I3) were randomly devoted in horizontal plots, hydrogel polymer at rate of 20 kg ha-1 as compared to normal soil (zero hydrogel) were assigned in vertical plots, while three weed control treatments (thiobencarb at 2.38 kg ai ha-1 at 9 days after sowing (DAS) followed by (fb) bispyribac-sodium at 0.038 kg ai ha-1 + halosulfuron-methyl at 0.036 Kg ha-1 applied at 25 DAS (W1), Thiobencarb at 2.38 kg ai ha-1 fb cyhalofop-butyl at 0.286 Kg ai ha-1 + halosulfuron-methyl at 0.036 Kg ha-1 applied at 25 DAS (W2) as compared to un-treated weedy check plots (W3) were allocated in endo/sub-sub plots. Results showed that irrigation every 10 and 15 days saved about 26.4% and 35.8% of applied water, respectively, while the yield reduced by 31.8% and 56.1% respectively compared to irrigation every 5-days as average of the two seasons. The lowest dry weights of grasses and total weeds were recorded of I1, while C. difformis weed was absent under I3 during 2020 and 2021 seasons. Hydrogel polymer application conserved about 14.8% of applied water and improved rice grain yield by 16.5% as well as increased water productivity to be 0.48 kg m-3 compared to 0.32 kg m-3 for without hydrogel treatment. Hydrogel encouraged C. difformis appearance while decreased grasses and total weeds compared to without hydrogel. Sequential herbicides application W1 recorded the best weed control against grasses, C. difformis and total weeds in addition to higher WCE (91.9%) against total weeds consequently produced the highest values of rice dry matter, yield and its attributes during both seasons of study. The interaction of I1 x hydrogel x W1 achieved the highest grain yield (10.11 t ha-1) with same significance for I1 x without hydrogel x W1 (9.75 t ha-1), while I2 x hydrogel x W1 recorded the highest water productivity (0.78 kg m-3) and produced 7.63 t ha-1 of rice grain yield by increasing of 20.7% than I2 x without hydrogel x W1 as average for 2020 and 2021 seasons.