Spatial variation in actual and required nitrogen use efficiency and the potential to close the gap by management practices

Age-related changes in nitrogen resorption and use efficiency in the perennial new crop Physaria mendocina (Brassicaceae)

Nitrogen (N) plays an important role in plant growth, development and also one of the major factor for developing a high-yielding rice cultivars. Nitrogen use efficiency (NUE) in plants is a complex phenomenon that depends on a number of internal and external factors, which include soil N availability, its uptake and assimilation of carbon and nitrogen. An increased awareness of the regulatory mechanisms controlling Nitrogen economy is imperative to enhance nitrogen uptake and use efficiency so as to reduce excessive input of fertilizers, while maintaining an acceptable yield. The physiological, biochemical, molecular aspects like QTL, mi RNA technology and transgenic approaches as well as NUE can be targeted to improve rice productivity. Yield being complex and multigenic trait linkages between carbon and nitrogen pathways are essential. An attempt on complex interactions between the two major physiological pathways linked by photosynthesis and photorespiration in global climate change for enhancing NUE in relation to rice yield was reviewed.

Efficiency use of nitrogen in several palm oil varieties with treatment in nitrogen fertilizer level in main nursery. This study aims to determine the growth characteristics of several varieties of palm oil efficient use of nitrogen with the provision of various nitrogen levels in the main nursery. The research was conducted in the nursery area of Yos Sudarso Binjai road and the Soil Laboratory of the Palm Oil Research Center, Medan from May to November 2017, using a factorial randomized block design with two factors. The first factor is varieties consisting of 7 types namely Avros, Simalungun, PPKS 540, Yangambi, PPKS 718, PPKS 239, Langkat. The second factor is the N fertilization dose consisting of 5 levels ie 0, 25, 50, 75 and 100% from fertilizer recommendation. The results showed that the addition of N level increased the dry weight of the canopy, and the uptake of plant N nutrients. The efficient use of optimal Nitrogen in Yangambi varieties was obtained on N 25% fertilization, while Avros and PPKS 239 were at 50% recommendation level. 75% recommendation produce optimal value efficient use of N on Simalungun variety, PPKS 718, and Langkat. PPKS 540 varieties efficient use of N optimal at 100% recommendation level.

Temporal and spatial variations in nitrogen use efficiency of crop production in China

The nitrogen use efficiency (NUE) is the ratio of the N uptake by the plant to the total amount of applied N fertilizer. The optimization of NUE is essential for sustainable agriculture, especially in the breeding programs to improve the yield of barley (Hordeum vulgare L.). We investigated the NUE variation in 32 barley genotypes and to examine the response relationship between phenotypic traits and N level to determine the traits essential for the selection of breeding programs to optimize the NUE. The NUE was investigated in 32 barley genotypes for 2 yr under field conditions using three N levels (60, 120, and 180 kg N ha−1). Growth, physiological and agronomic traits, and N efficiency‐related parameters were determined. The parameters investigated were significantly affected by N application and its interactions with traits. Plant height, biological yield, spike length, and grain number (GN) were increased at higher N levels, but the 1,000‐grain weight decreased. The lowest grain yield was 2,000.7 kg ha−1 at 60 kg N ha−1, and the highest was 8,607.9 kg ha−1 at 120 kg N ha−1. An increase in the N rate from 60 to 120 kg N ha−1 was associated with a higher total chlorophyll content (CHLSPAD) (from 19.04 to 23.13), but no significant change in CHL was seen at 180 kg N ha−1. The agronomic nitrogen use efficiency (ANUE), fertilizer N recovery efficiency and the nitrogen utilization efficiency were both reduced with an increase of the N application rate. A path analysis revealed that GN was the most essential trait for NUE breeding program selection due to its high direct effect (0.72) on ANUE. A linear discriminant analysis showed that CHL at 60 d after sowing was the best trait for distinguishing low from high N levels.

Rice–wheat (RW) cropping systems are integral to global food security. Despite being practiced for decades, Chinese RW cropping systems often suffer from low productivity and poor nitrogen use efficiency (NUE), reflecting management approaches that are not well-contextualized to region and season. Here, we develop the best management guides for N fertilizer in RW systems that are designed to help raise the productivity, NUE, and environmental sustainability of winter wheat over the long term. 2-year field experiments were conducted with four N fertilizer rates (0, 135, 180, and 225 kg N ha–1), allowing contrasts of yields, soil moisture, and NUE of wheat in RW in the humid climates zones on the Jianghan Plain. We compared RW systems with soybean/maize dryland wheat (DW) systems that are similarly endemic to China: after soybean/maize is harvested, soils are often drier compared with moisture content following rice harvest. With high seasonal N application rates (180–225 kg N ha–1), wheat crop yields increased by 24% in RW which were greater than comparable yields of wheat in DW, mainly due to greater kernels per spike in the former. Across treatments and years, N accumulation in plant tissue and kernel dry matter of DW was higher than that in RW, although mean agronomic efficiency of nitrogen (AEN) and physiological efficiency of nitrogen (PEN) of RW systems were greater. As N application rates increased from 135 to 225 kg ha–1, AEN and PEN of DW decreased but changed little for RW. Soil ammonium N was much lower than that of nitrate N; changes in NH4+ and NO3– as a consequence of increasing N fertilization were similar for RW and DW. We recommend that tactical application of N fertilizer continue seasonally until midgrain filling for both the DW and RW systems. At fertilization rates above 180 kg N ha–1, yield responses disappeared but nitrate leaching increased significantly, suggesting declining environmental sustainability above this N ceiling threshold. Collectively, this study elicits many functional and agronomic trade-offs between yields, NUE, and environmental sustainability as a function of N fertilization. Our results show that yield and NUE responses measured as part of crop rotations are both more robust and more variable when derived over multiple seasons, management conditions, and sites.

Nitrogen (N) is an important macro-nutrient required for crop production and is considered an important commodity for agricultural systems. Urea is a vital source of N that is used widely across the globe to meet crop N requirements. However, N applied in the form of urea is mostly lost in soil, posing serious economic and environmental issues. Therefore, different approaches such as the application of urea coated with different substances are used worldwide to reduce N losses. Urea coating is considered an imperative approach to enhance crop production and reduce the corresponding nitrogen losses along with its impact on the environment. In addition, given the serious food security challenges in meeting the current and future demands for food, the best agricultural management strategy to enhance food production have led to methods that involve coating urea with different nutrients such as sulfur (S) and zinc (Zn). Coated urea has a slow-release mechanism and remains in the soil for a longer period to meet the demand of crop plants and increases nitrogen use efficiency, growth, yield, and grain quality. These nutrient-coated urea reduce nitrogen losses (volatilization, leaching, and N2O) and save the environment from degradation. Sulfur and zinc-coated urea also reduce nutrient deficiencies and have synergetic effects with other macro and micronutrients in the crop. This study discusses the dynamics of sulfur and zinc-coated urea in soil, their impact on crop production, nitrogen use efficiency (NUE), the residual and toxic effects of coated urea, and the constraints of adopting coated fertilizers. Additionally, we also shed light on agronomic and molecular approaches to enhance NUE for better crop productivity to meet food security challenges.

Straw returning inhibits tillering at the early stage of rice growth and thus affects grain yield. Sulfur-coated urea (SCU) has been expected to increase nitrogen use efficiency (NUE) and yield, save labor input, and reduce environmental pollution in crop production. Nevertheless, the sulfur coatings of SCU are easy to break and then shorten the nutrient release cycle. Whether there was a complementary effect between straw returning and SCU in NUE and grain yield had remained elusive. To investigate the effects of straw returning combined with the application of SCU on NUE and rice yield, a two-year field experiment was conducted from 2022 to 2023 with three treatments (straw returning combined with conventional urea (SRU), no straw returning combined with SCU (NRS), straw returning combined with SCU (SRS)). We found that straw returning combined with the application of SCU increased rice yield and NUE significantly. Compared with SRU and NRS, SRS treatments significantly increased grain yield by 14.61–16.22%, and 4.14–7.35%, respectively. Higher effective panicle numbers per m2 and grain numbers per panicle were recorded in NRS and SRS treatments than SRU. SRS treatment increased nitrogen recovery efficiency by 79.53% and 22.97%, nitrogen agronomic efficiency by 18.68% and 17.37%, and nitrogen partial factor productivity by 10.51% and 9.81% compared with SRU and NRS treatment, respectively. The enhanced NUE in SRS was driven by higher leaf area index, SPAD value, net photosynthetic rate, carbon metabolic enzyme (RuBP and SPS) activity, nitrogen metabolic enzyme (NR, GS, and GOGAT) activity, sucrose and nitrogen content in leaves, and nitrogen accumulation in plant during grain filling. Moreover, the improved yield in SRS was closely related to superior NUE. In conclusion, straw returning combined with application of SCU boosted grain yield and NUE via enhanced carbon–nitrogen metabolism during the late growth period in rice.

The aims of this study were to determine water, nitrogen and energy use efficiency in major crop production of Kermanshah province, western of Iran such as wheat, corn, alfalfa and sugar beet. Data was collected applying questionnaires via face to face interviews with 200 farmers (50 farmers for each crop) in 2014. Results showed total nitrogen fertilizer input in wheat, corn, alfalfa and sugar beet were 358.7, 580.57, 200 and 653.91 kg/ha, respectively. In the other hand, total irrigated water in wheat, corn, alfalfa and sugar beet was 5850, 8669.2, 6563.7 and 11880 m3/ha, respectively. Accordingly, nitrogen use efficiency (NUE) was 15.81, 19.51, 67.55 and 99.71 kg/kg for corn, wheat, alfalfa and sugar beet respectively. In this research water use efficiency (WUE) in wheat, corn, alfalfa and sugar beet was 1.20, 1.06, 2.06 and 5.49 m 3 /ha respectively. In this study total output and input energy were 60832.52 and 184150 Mj/ha in wheat agroecosystems, 50485.42 and 134946 Mj/ha in corn agroecosystems, 49689.59 and 240072.7 Mj/ha in alfalfa agroecosystems and 49517.2 and1095360 Mj/ha in sugar beet agroecosystems. Energy use efficiency (EUE) was 2.67, 3.03, 4.83 and 22.12 in corn, wheat, alfalfa and sugar beet production, respectively. Hence, the highest amount of WUE, NUE and EUE were observed in sugar beet and then alfalfa and wheat respectively and lowest amounts were observed in corn agroecosystems.

Anbessa, Y. and Juskiw, P. 2012. Review: Strategies to increase nitrogen use efficiency of spring barley. Can. J. Plant Sci. 92: 617–625. Improvement in nitrogen use efficiency (NUE) is important to reduce input costs and the negative impact of excessive N on the environment. This review found that barley growers in western Canada have over the years adopted a number of improved N management strategies including soil testing and adjusting rate of N fertilization accordingly, switching from fall application to spring application of N fertilizers, and side-dressing placement of N that gives plant roots easier access to N nutrition. However, it is our opinion that use of variable N rates, choice of N fertilizer type that is less susceptible to losses, and improved manure management are some of the areas where further increase in NUE should be sought. As well, barley germplasms show substantial differences in NUE and genetic selection could increase NUE. Genetic improvement of NUE in barley should be possible both by the traditional breeding approach of crossing and pyramiding NUE genes from across different sources as well as through the development of transgenic barley. The integration of improved N management practices and more efficient cultivars may bring about a significant increase in NUE and ultimately grain yield of barley under the target moderate rate of N application.

Experiments were conducted at the Department of Crop Science, University of Nigeria, Nsukka Research farm during the 2008 and 2009 cropping seasons to determine the effects of intercropping cassava and soybean on cassava tuber and soybean grain yields respectively and on nitrogen use efficiency of cassava at the intercropping system. The experiment for each year was laid out in a factorial arrangement in randomized complete block design (RCBD). The treatments were the nitrogen rates, sole soybean (TGM 579), sole cassava (TMS 30572) and cassava + soy bean intercrop. Intercropping cassava with soybean showed a significant (P ≤ 0.05) yield advantage over sole cropping system in 2008. Increased fertilizer rates up to 90 kg N/ha -1 increased fresh cassava yield in sole cropping system, while in the intercrop, increased application of nitrogen at 60 kg N decreased cassava tuber yield. The cassava nitrogen use efficiency (NUE) increased with increase in applied nitrogen up to 60 kg N/ha -1 and then decreased beyond this point. Similar trend was observed in 2009, except that total harvested cassava tuber yield was significantly higher in 2009 than that obtained in 2008. This result suggests that intercropping cassava with soybean with or without application of nitrogen is beneficial but high doses of nitrogenous fertilizer in sole soybean field is uneconomical and should be avoided. Key words: Cassava, soybean, intercrop, sole crop, nitrogen use efficiency.

Effects of different stocking density start-up conditions on water nitrogen and phosphorus use efficiency, production, and microbial composition in aquaponics systems

Addressing the challenge of reducing environmental pollution from agricultural practices by improving nitrogen use efficiency (NUE) and water use efficiency (WUE) while ensuring high crop yields is essential for sustainable agriculture. Using a controlled glasshouse experiment, we evaluated the combined effects of biochar and bokashi under different irrigation regimes on NUE, WUE, and yield-related parameters in a wheat cropping system. The experiment followed a completely randomized design with three replications with four treatments: (1) control (C), (2) bokashi only (B0), (3) bokashi +1% biochar (B1), and (4) bokashi +2% biochar (B2). These treatments were evaluated at three irrigation levels—30% (IR30), 50% (IR50), and 60% (IR60) of field capacity (FC), resulting in a total of twelve treatments. Co-application of bokashi–biochar significantly (p < 0.050) improved grain yield (GY), straw yield (SY), total biomass (TB), total nitrogen uptake (TNU), grain protein content (GPC), NUE, and WUE, with the most notable benefits observed at 1% biochar application compared to C and B0 treatments. In addition, both types of treatment (bokashi and bokashi with biochar) and the level of irrigation had a significant impact on GY, SY, TB, TNU, GPC, NUE, and WUE. The B1 and B2 treatments further improved yield and efficiencies compared to bokashi alone. The positive correlation between grain yield and WUE underscores the importance of optimizing irrigation strategies alongside soil amendments for improved crop productivity. These enhancements in yield and efficiency are likely attributed to the increased soil fertility, nutrient availability, and water retention resulting from the combination of biochar and bokashi.

Anbessa, Y. and Juskiw, P. 2012. Review: Strategies to increase nitrogen use efficiency of spring barley. Can. J. Plant Sci. 92: 617-625. Improvement in nitrogen use efficiency (NUE) is important to reduce input costs and the negative impact of excessive N on the environment. This review found that barley growers in western Canada have over the years adopted a number of improved N management strategies including soil testing and adjusting rate of N fertilization accordingly, switching from fall application to spring application of N fertilizers, and side-dressing placement of N that gives plant roots easier access to N nutrition. However, it is our opinion that use of variable N rates, choice of N fertilizer type that is less susceptible to losses, and improved manure management are some of the areas where further increase in NUE should be sought. As well, barley germplasms show substantial differences in NUE and genetic selection could increase NUE. Genetic improvement of NUE in barley should be possible both by the traditional breeding approach of crossing and pyramiding NUE genes from across different sources as well as through the development of transgenic barley. The integration of improved N management practices and more efficient cultivars may bring about a significant increase in NUE and ultimately grain yield of barley under the target moderate rate of N application.

The optimization of plant density plays a crucial role in cotton production, and deficit irrigation, as a water-saving measure, has been widely adopted in arid regions. However, regulatory mechanisms governing nitrogen absorption, transportation, and nitrogen use efficiency (NUE) in cotton under deficit irrigation and high plant density remain unclear. To clarify the mechanisms of N uptake and NUE of cotton, the main plots were subjected to three irrigation amounts based on field capacity (Fc): (315 [W1, 0.5 Fc], 405 [W2, 0.75 Fc, farmers’ irrigation practice], and 495 mm [W3, 1.0 Fc]). Subplots were planted and applied at three densities: (13.5 [M1], 18.0 [M2, farmers’ planting practice], and 22.5 [M3] plants m−2). The results revealed that under low-irrigation conditions, the cotton yield was 5.1% lower than that under the farmer’s irrigation practice. In all plant densities and years, the nitrogen uptake of cotton increased significantly with the increase in irrigation. However, excessive irrigation resulted in nitrogen accumulation and migration, mainly concentrated in the vegetative organs of cotton, which reduced the NUE by 9.2% compared with that under farmers’ irrigation practice. Concerning the interaction between irrigation and plant density, under low irrigation, the nitrogen uptake of high-density planting was higher, and the yield of seed cotton was only 2.9% lower than that of the control (the interaction effect of farmers’ irrigation × plant density), but the NUE was increased by 10.9%. Notably, with the increase in irrigation amount, the soil nitrate nitrogen at the 0–40 cm soil layer decreased, and high irrigation amounts would lead to the transfer of soil nitrate nitrogen to deep soil. With the increase in plant density, the rate of nitrogen uptake and the amount of nitrogen uptake increased, which significantly reduced the soil nitrate nitrogen content. In conclusion, deficit irrigation and high plant density can improve cotton yield and NUE. We anticipate that these findings will facilitate optimized agricultural management in areas with limited water.