Nitrogen deficiency tolerance and responsiveness of durum wheat genotypes in Ethiopia

Development of low-nitrogen (N) tolerant and N-responsive durum wheat genotypes is required since nitrogen efficiency has emerged as a highly desirable trait from economic and environmental perspectives. Two hundred durum wheat genotypes were evaluated at three locations under optimum (ON) and low (LN) nitrogen conditions to screen genotypes for low-nitrogen tolerance and responsiveness to an optimum N supply. The results showed significant variations among the durum wheat genotypes for low-N tolerance and responsiveness. The average reduction in grain yield under the LN condition was 48.03% across genotypes. Only 17% of the genotypes tested performed well (grain yield reduction <40%) under LN conditions. Based on the absolute grain yield, biomass yield, and normalized difference vegetative index value, on average, 32, 14, 17, and 37% of the tested genotypes were classified as efficient and responsive, efficient and nonresponsive, inefficient and responsive, and inefficient and nonresponsive, respectively. Considering the absolute and relative grain yield, biomass yield, normalized difference vegetative index values, and stress tolerance indices as selection criteria, 17 genotypes were chosen for subsequent breeding. Among the screening indices, geometric mean productivity, stress tolerance index, yield index, and stress susceptibility index exhibited positive and significant correlations with grain yield under both N conditions; hence, either of these traits can be used to select low-N-tolerant genotypes. The common genotypes identified as LN-tolerant and responsive to N application in this study could be used as parental donors for developing N-efficient and responsive durum wheat varieties

Improved Bread and Durum Wheat Cultivars Showed Contrasting Performances in N-Efficiency and N-Responsiveness

Wheat productivity can be increased by applying nitrogen (N) in the form of chemical fertilizers. However, owning to the high prices, chemical fertilizers are unaffordable to resource-poor farmers in Ethiopia. The use of N-efficient cultivars rather makes an alternative option for sustainable wheat production. Six bread and six durum wheat cultivars were thus evaluated under low N (1 g·pot−1) and optimum N (5 g·pot−1) in six replications. The pot-based treatments were arranged in randomized complete block design in the lathe house at Kulumsa Agricultural Research Center. Results showed that the number of effective tillers (NET), spike length (SL), total dry biomass yield (TBY), grain yield (GY), NDVI values, total N uptake (TNUP), N utilization efficiency (NUtE), N uptake efficiency (NUpE), N use efficiency (NUE), grain, and straw N uptakes were significantly influenced by wheat cultivars and N levels. Under low N, Hidase and Kingbird gave significantly higher GY, whereas Danda’a and Hidase gave significantly higher GY under optimum N. Under low N, Hidase, Kingbird, and Lemu were identified as the most N-efficient, while Ude, Landrace, and Utuba identified as N-inefficient based on multicriterion performance (GY, TBY, SL, NET, TNUP, NHI, NUpE, NUtE, and NUE). Under optimum N, Danda’a, Shorima, Hidase, and Lemu were identified as the most responsive, while Ude, Landrace, and Kingbird identified as nonresponsive to N application. In conclusion, Kingbird is recommended for low N input, while Danda’a and Shorima are recommended for N input intensive, and Hidase and Lemu are recommended for both low and high N input intensive wheat production

Yield Response and Nutrient Use Efficiencies under Different Fertilizer Applications in Maize (Zea mays L.) In Contrasting Agro Ecosystems

Variability in crop response and nutrient use efficiencies to fertilizer application is quite common under varying soil and climatic conditions. Understanding such variability is vital to develop farm- and area- specific soil nutrient management and fertilizer recommendations. Hence the objectives of this study were to assess maize grain yield response to nutrient applications for identifying yield-limiting nutrients and to understand the magnitude of nutrient use efficiencies under varying soil and rainfall conditions. A total of 150 on-farm nutrient omission trials (NOTs) were conducted on farmers’ field in high rainfall and moisture stress areas. The treatments were control, PK, NK, NP, NPK and NPK+ secondary and micronutrients. Maize grain yield, nutrient uptake, agronomic and recovery efficiencies of N and P differed between fertilizer treatments and between the contrasting agro-ecologies. The AEN ranged from 24.8 to 32.5 kg grain kg-1 N in Jimma area and from 1.0 kg grain kg-1 N (NK treatment) to 10.2 kg grain kg-1 N (NPK treatment) at Adami Tullu and from 0.1 kg grain kg-1 N (NK treatment) to 8.3 kg grain kg-1 N (NPK treatment) at Bulbula. The differing parameters between the agro-ecologies were related to difference in rainfall amount and not to soil factors. Grain yield response to N application and agronomic efficiencies of N and P were higher in the high rainfall area than in the moisture stress areas. Grain yield responded the most to nitrogen (N) application than to any other nutrients at most of the experimental sites. Owing to the magnificent yield response to N fertilizer in the current study, proper management of nitrogen is very essential for intensification of maize productivity in most maize growing areas of Ethiopia

Low Nitrogen Narrows down Phenotypic Diversity in Durum Wheat

AbstractBreeding for nitrogen use efficiency has become the major global concern and priority to improve agricultural sustainability. In an attempt to quantify genetic variation and identify traits for optimum and low N environments, 200 durum wheat genotypes were evaluated at three locations in the central highlands of Ethiopia during the 2020 growing season. The experiments were arranged in alpha lattice design with two replications. The results revealed significant differences among genotypes for all studied traits under both N conditions, indicating ample opportunities for genetic improvement. All traits except days to heading and maturity, grain filling period and grain protein content were higher under optimum than under low N. High values of genotypic and phenotypic coefficients of variations, broad sense heritability and genetic advance as percent of the mean were observed for number of fertile tillers and number of seed per spike (NSPS) under optimum, and spike length and NSPS under low N conditions. Cluster analysis classified the durum wheat genotypes into thirteen and eight clusters under optimum and low N, respectively. Principal component analysis detected five and four components which explained 81.29% and 73.63% of the total variations under optimum and N stress conditions, respectively. The present study confirmed the existence of wide genetic variability among the durum wheat genotypes under optimum and low N conditions; and low N lowers the level of diversity. Thus, our study paves the possibility for improvement of durum wheat genotypes through selection and hybridization for increased grain yield and adaptation to N stressed conditions

Nitrogen Deficiency Tolerance and Responsiveness of Durum Wheat Genotypes in Ethiopia

Development of low-nitrogen (N) tolerant and N-responsive durum wheat genotypes is required since nitrogen efficiency has emerged as a highly desirable trait from economic and environmental perspectives. Two hundred durum wheat genotypes were evaluated at three locations under optimum (ON) and low (LN) nitrogen conditions to screen genotypes for low-nitrogen tolerance and responsiveness to an optimum N supply. The results showed significant variations among the durum wheat genotypes for low-N tolerance and responsiveness. The average reduction in grain yield under the LN condition was 48.03% across genotypes. Only 17% of the genotypes tested performed well (grain yield reduction <40%) under LN conditions. Based on the absolute grain yield, biomass yield, and normalized difference vegetative index value, on average, 32, 14, 17, and 37% of the tested genotypes were classified as efficient and responsive, efficient and nonresponsive, inefficient and responsive, and inefficient and nonresponsive, respectively. Considering the absolute and relative grain yield, biomass yield, normalized difference vegetative index values, and stress tolerance indices as selection criteria, 17 genotypes were chosen for subsequent breeding. Among the screening indices, geometric mean productivity, stress tolerance index, yield index, and stress susceptibility index exhibited positive and significant correlations with grain yield under both N conditions; hence, either of these traits can be used to select low-N-tolerant genotypes. The common genotypes identified as LN-tolerant and responsive to N application in this study could be used as parental donors for developing N-efficient and responsive durum wheat varieties

Nitrogen use efficiency and genotype-by-environment interaction in durum wheat genotypes under varying nitrogen supply

Nitrogen (N) use efficiency is important for wheat grain yield and quality. This study evaluated6 durum wheat genotypes in Ethiopia to determine the extent of nitrogen use efficiency (NUE) components and genotype-by-environment interactions under high and low N supply. The results showed that there was significant variation among the genotypes in grain yield and NUE components. Grain yield ranged from 3.30 to 6.22 t ha−1 under high N and 2.30 to 3.78 t ha−1 under low N conditions with an average reduction of 40.1%. Nitrogen harvest index, Nitrogen uptake efficiency (NUpE), Nitrogen utilization efficiency (NUtE) and NUE increased under low N compared to high N. NUtE varied from 28.6 to 43.9 kg kg−1 under high N and 39.5 to 51.2 kg kg−1 under low N while NUE increased from 26.4 under high N to 31.8 kg kg−1 under low N. Grain yield showed significant and positive associations with most of NUE components under both N conditions. NUpE and NUtE are the two important traits that contribute to NUE. N-efficient genotypes were found to be the most stable genotypes. Thus, the study emphasizes the importance of selecting genotypes with improved grain yield and NUE traits under low N conditions.</p