Comparative assessment of urea briquette applicators on greenhouse gas emission, nitrogen loss and soil enzymatic activities in tropical lowland rice

Mechanized transplanting with side deep fertilization increases yield and nitrogen use efficiency of rice in Eastern China

“…The urease activity was lower in UM and CRUM than in UB through the whole late growth period, which prolonged N availability to rice roots. These results, which will be reported in detail in another study, are consistent with those of previous studies 42 . The deep placement of N fertilizer obviously decreased nitrate reductase and nitrite reductase in 0–25 cm soil, which weakened the conversion of - into - or -.…”

“…The BCR and net income were highest in CRUM, followed by UM, and lowest in UB. The combination of higher gross return and lower fertilization cost in CRUM resulted in higher BCR and net income, consistent with previous results 37,42 . In those studies, grain yield and net economic return were increased by deep fertilization of either urea briquettes or N-P-K briquettes compared with broadcasting prilled (pelletized) urea, while deep fertilization of either urea briquettes or N-P-K briquettes reduced N fertilizer use and increased rice production.…”

“…This finding was not consistent with those of a previous study 41 . The mechanical placement of U and CRU at 5.5 ± 0.5 cm soil depth beside seedlings would inevitably create a special root microenvironment zone because of the longer persistence of -N in the soil 31,42,43 . Compared to deep placement of U, CRU did not significantly increase the number of productive panicles, because multiple seedlings in each hole produced the rapid tiller growth during the early growth stage of the densely distributed seedlings, and the N demands of rice after the heading stage were fully met by the continuous supply of N from CRU, resulting in increased grain number per panicle in the early season.…”

“…This implied that N losses were lower in CRUM and UM than in UB. The deep application of N fertilizer (UM and CRUM) increased N uptake by: (1) reducing N 2 O emission 47 and NH 3 volatilization 14 ; (2) decreasing surface runoff 31,43 ; (3) increasing the -N and -N concentrations in soil 31,42,43 ; and (4) synchronizing N availability with plant N demands. The N uptake from the panicle initiation stage to the maturity stage was significantly higher in the mechanically applied N fertilizer treatments (irrespective combinations of N fertilizer applied) than in the manual surface broadcasting treatment.…”

Understanding interaction effect of arbuscular mycorrhizal fungi in rice under elevated carbon dioxide conditions

“…The soil enzymes, particularly fluorescein diacetate activity (FDA), dehydrogenase activity (DHA), acid phosphatase (AcP), and alkaline phosphatase (AkP), were determined using the ultraviolet‐visible spectrophotometric procedures. Soil FDA was measured using the chloroform/methanol (2:1) method , DHA measured by the reduction of triphenyl tetrazolium chloride method , and AcP and AkP, using modified universal buffers having pH 6.5 and 11.5, respectively .…”