Differences in seasons and rice varieties provide opportunities for improving nitrogen use efficiency and management in irrigated rice in Kenya

Abstract

Apart from nitrogen (N) rates, N use efficiency (NUE) (yield N/total input N) is affected by seasons, crop developmental stages, and varieties. Knowledge of how these factors affect NUE in rice production in Kenya is limited. Therefore, field experiments were conducted with ‘low rates’ of N (simulating farmers’ practices) of 0, 26, 52 and 78 kg N ha−1 with five varieties (MWUR1, MWUR4, IRAT109, NERICA4 and NERICA10) and higher rates of N (125, 175, and 225 kg N ha−1) simulating researchers’ doses with two lowland varieties (Basmati 370 and BW 196) and IR 72. Another experiment on NUE responses to sites, N rates and dose (split or full dose) was undertaken with the IR97 variety. With the ‘low rate’, yields increased with incremental N rates up to 52 Kg N ha−1 and declined (during cold periods, for some varieties). In this scenario, the N agronomic efficiencies (AEN) declined with increasing N but depended on sites and seasons. However, most AEN values were above 100, implying nutrient mining. In most cases (except at the Mwea site), the N utilization efficiency (NUtE) ranged from 16 to 22kg kg−1 and were not significantly affected by sources and methods of N application. In all cases, an increase in N elicited declining trends in NUtE. Moreover, N uptake efficiency ranged between 22 and 90kg kg−1 without significant variation among varieties. For the ‘high N rates’, high biomass yield resulted in higher grain yields in BW 196 and IR 72 but yield declined beyond 75 kg ha−1 N rates due to poor grain filling, particularly when a cold period coincided with booting and grain filling. We conclude that N rates, doses and rice varieties are key determinants of AEN and NUtE in contrasting rice growing seasons in Kenya. Cropping seasons and rice varieties are therefore potential key determinants of sustainable rice productivity and improved NUE in rice-based systems in the studied regions of Kenya.

Simulation of the critical nitrogen dilution curve in Jiangxi double-cropped rice region based on leaf dry matter weight

“…Different rice genotypes have different sensitivities to nitrogen fertilizer [ 27 ]. In this study, parameter b from rice variety ‘Zhongjiazao’ was greater than that from rice variety ‘Changliangyou 173’, parameter b from rice variety ‘Fumeizhan’ was smaller than that from rice variety ‘Taiyouhang 1573’, while parameter a exhibited uncertainty.…”

Nitrogen use efficiency trends for sustainable crop productivity in Lake Victoria basin: smallholder farmers’ perspectives on nitrogen cycling

“…This was partly due to better N use influences in rice through enhanced panicle formation and grain filling process that are key yield components (Sun et al 2018). Gweyi-Onyango et al (2021) suggested that more yield in rice could be realized if a synchrony between the crop N demand and N availability is maintained during the growing period and this had an indirect bearing on NUEs. The higher yield in some rice farms with higher N application is an indication that with more N inputs, the challenge of food insecurity would be solved (Mafongoya et al 2006).…”

Recent trends in nitrogen cycle and eco-efficient nitrogen management strategies in aerobic rice system

“…Improvements in NUE under aerobic rice systems and other non-N 2 -fixing crops are required to fulfill the future food requirements of the projected inflation in the population via improved and modified N-use efficient varieties along with other crops, irrigation, and fertilizer management practices ( Mboyerwa et al, 2021 ). Management practices that focus on improving plant N uptake and NUE involve irrigation methods, fertilizer input management, crop variety management in terms of water and NUE, plant N uptake management, use of controlled-release N fertilizers, use of NIs and urease inhibitors for synthetic N fertilizers, and other agronomic integrative crop management approaches ( Pan et al, 2017 ; Gweyi-Onyango et al, 2021 ; Williams et al, 2021 ; Ebbisa, 2022 ; Ma X. et al, 2022 ). Several studies regarding NUE have demonstrated that it is majorly associated with the type and method of fertilizer inputs, irrigation methods, availability of soil N, and plant N uptake ( Ye et al, 2013 ; Rawal et al, 2022 ).…”