Aboveground Nitrogen Uptake Research Articles

Alternate furrow irrigation improves grain yield and nitrogen use efficiency in winter wheat

The objective of this study was to determine whether grain yield and nitrogen (N) use efficiency (NUE) in winter wheat (Triticum aestivum L.) could be improved by alternate furrow irrigation (AFI). During the 2009–2010 and 2010–2011 crop seasons, the effects of AFI on grain yield, NUE (and its components), the recovery of 15N-labeled fertilizer, N uptake and distribution, and soil nitrate-N were evaluated under field conditions. The irrigation regimes were: W0, non-irrigated; W2, every furrow irrigated at jointing and anthesis; W3, every furrow irrigated before wintering and at jointing and grain filling; and AFI, each of two neighboring furrows irrigated either before wintering or at grain filling, and every furrow irrigated at jointing. Our results show that grain yield, above-ground nitrogen uptake (AGN; including N from fertilizers and soil), and NUE were lowest in the W0 treatment and tended to increase with increasing irrigation frequency. Grain yield, AGN (including N from fertilizers and soil), NUE, nitrogen uptake efficiency (UPE), 15N-recovery efficiency, and N accumulation in grains were significantly higher in the AFI treatment than in the W2 treatment. AGN increased due to a higher amount of N derived from both fertilizers and soil. More N was derived from soil than from fertilizers; thus, the proportion of N derived from fertilizers decreased. No significant differences in grain yield and NUE were observed between the AFI and W3 treatments. AGN decreased when soil N luxury uptake and N accumulation in stems and leaves decreased. Greater N utilization efficiency and a higher N harvest index were observed in the AFI treatment compared with the W3 treatment. In addition, AFI increased nitrate-N contents in the upper soil layer (0–60 cm) and reduced nitrate-N movement to deeper soil compared to the W2 and W3 treatments. Therefore, AFI may be an appropriate irrigation method for improving NUE and decreasing water consumption in winter wheat without reducing yield.

Winter Wheat Yield and DSSAT Model Evaluation in a Diverse Semi-Arid Climate and Agronomic Practices

Because of human dependence on sustainable food production, it is needed to adopt agricultural production to climate change, and their consequences on associated socioeconomic issues. Crop modelling potentially can contribute to global food and nutrition security. Therefore, in this context DSSAT (decision support system for agro-technology transfer) was validated for predicting growth and yield of wheat under a diverse semi-arid climate (2 years with diverse climates) and different irrigation strategies, planting methods, and nitrogen rates. The irrigation strategies were ordinary furrow irrigation (OFI) and variable alternate furrow irrigation (VAFI), and the planting methods were on-ridge planting (ORP) and in-furrow planting (IFP) methods. The fertilizer levels were 0 (N0), 150 (N1) and 300 (N2) kg N ha−1. Results indicated that water stress and inappropriate weather especially during the stem elongation influences the grain yield remarkably without noticeable effect on straw yield. Furthermore, VAFI strategy did not impose any limitation on top dry matter N concentration in both years. Calibration of DSSAT showed that the model underestimated the actual evapotranspiration at the end of growing season (during spring with high temperature) and resulted in overestimating the soil water content at depths under 10 cm during this period of time. Since the potential transpiration has an important role in calculating the effect of water stress factor, the model overestimated slightly the maximum leaf area index (LAI) and consequently biomass and yield in water stress condition; however, overall, model could statistically simulate LAI (NRMSE = 0.3, d = 0.96, R2 = 0.95), total dry matter (NRMSE = 0.07, d = 0.99, and R2 = 96) and grain yield (NRMSE = 0.13, d = 0.96, and R2 = 90). Model also could reasonably simulate the nitrogen components including the grain N concentration (NRMSE = 0.05, d = 0.95), above-ground nitrogen uptake (NRMSE = 0.11, d = 0.99), and soil nitrate content (NRMSE = 0.23, d = 0.86). However, evaluating the model with data set from 2015 to 2016 indicated that the model could not simulate wheat yield and nitrogen components in validation year due to strong effects of diverse weather condition and water stress on grain yield and crop development.

Effects of Returning Nitrogen by Biochar Loading on Paddy Growth, Root Morphology, and Nitrogen Use Efficiency

Building a nutrient channel between eutrophic water and agricultural fields could reduce nutrient input into fields and alleviate eutrophication by returning nitrogen. In order to determine the feasibility of returning nitrogen by biochar loading, a rhizobox experiment was conducted with two nitrogen applied methods, namely SN (applied nitrogen by nitrogen fertilizer solution) and BN (applied nitrogen by nitrogen-loaded biochar). The results showed that BN, in comparison with SN, decreased the biomass and nitrogen uptake of the aboveground paddy by 16% and 14%, respectively, increased biomass root-shoot ratios by 25%-27%, and reduced nitrogen recovery use efficiency. Two nitrogen application methods affected the length and volume of paddy adventitious roots. Paddy underground biomass and nitrogen uptake were positively correlated with soil ammonium content, whereas paddy aboveground nitrogen uptake was negatively correlated with root tips. It was suggested that the paddy biomass and nitrogen uptake would be influenced when nitrogen was applied solely by nitrogen-loaded biochar. However, no affinity and no significance in nitrogen use efficiency were found for plant uptake between chemical nitrogen and biochar-loaded nitrogen. Additionally, biochar promoted soil mineral nitrogen content for further plant uptake. Therefore, biochar could be used as the carrier for returning nitrogen from waterbodies to fields. The replacement rate of chemical nitrogen fertilizer is the key to influencing plant growth and needs future study.

Responses of candidate green super rice and super hybrid rice varieties to simplified and reduced input practice

Producing higher grain yield with less environmental impact is a challenge for the future of agriculture. Breeding green super rice (GSR) varieties is one of the promising ways to meet this challenge. Green super rice is supposed to have better performance than super hybrid rice (SHR) under reduced input condition. In the present study, seven elite candidate GSR varieties and five representative SHR varieties were planted under the farmers’ practice (FP) and the simplified and reduced input practice (SRIP) in 2015 and 2016. The objectives were to compare the grain yield and NUE of the candidate GSR and SHR under FP and SRIP, and investigate the agronomic and physiological traits of GSR. Averaged across all varieties, the reduction in grain yield at SRIP compared to FP was 1.04 t ha−1 in 2015 (10.37%) and 0.50 t ha−1 in 2016 (5.55%). The average grain yield of GSR varieties was similar to that of SHR in 2015, but SHR had significantly greater (7.42%) average grain yield than GSR in 2016. In comparison to FP, yield reduction at SRIP for the candidate GSR and SHR varieties was 9.27% and 11.48% respectively in 2015, and 4.74% and 5.85% respectively in 2016. Grain yield of FP was significantly correlated with that of SRIP (R2 = 0.73). Averaged across varieties, total aboveground nitrogen uptake and nitrogen use efficiency for grain production between GSR and SHR were comparable. Among the GSR varieties, 9Y6H exhibited relative high yield stability and NUEg across treatments and planting years; however, SHR varieties showed consistently better yield stability than most of the GSR varieties. Overall, candidate GSR varieties had similar response to SRIP with the SHR varieties. In addition to breeding GSR varieties, future studies should also focus on the green traits of the SHR varieties.

Monitoring wheat fields by RapidScan: accuracy and limitations

Simple active radiometer sensors, such as RapidScan, enable agronomic decision-making and phenotyping within commercial wheat fields and experiments. The objectives of this study were: 1 - to evaluate the accuracy of quantitative biomass and nitrogen uptake estimation by the RapidScan, and 2 - to evaluate yield loss estimation based on NDVI. The RapidScan sensor was used as an assessment tool in the following studies: (i) over 3 years, 518 wheat samples were monitored during the vegetative growth period for biomass and aboveground nitrogen uptake and (ii) wheat cultivars were tested in an additional 4 field experiments, which were scanned weekly and correlated with grain yield. Results showed that accurate biomass estimation is limited up to about 100 g DM m−2. Grain yield, actual and potential, estimation is highly affected by the emergence date. The results showed that the use of a proximal-sensing technique allows for rapid and accurate crop monitoring and yield estimation, but emphasizing limitations in future use as well.

Investigation and synthesis of sweet sorghum crop responses to nitrogen and potassium fertilization

Optimizing nutrient management practices in cropping systems is essential to improve economic and environmentally sustainability. Sweet sorghum [Sorghum bicolor (L.) Moench] is a crop that is capable of high sugar, grain, and lignocellulosic biomass yields, but a synthesis of published nutrient response curves reveals gaps in our knowledge. We therefore evaluated responses of sweet sorghum on a marginal North Florida sandy soil to ranges in nitrogen and potassium application rates and combined the nitrogen data with literature datasets to provide a broadly useful assessment of the relationship between nitrogen uptake and yield. There were no significant effects of the application of potassium observed. In response to nitrogen, leaf SPAD and photosynthesis were less with 20kgNha−1 than with more nitrogen (60, 100, and 140kgha−1), reflecting end-of-season crop responses in total biomass, estimated sugar, and grain yield. A linear plateau model indicated that application of 70kgNha−1 was sufficient to optimize total biomass yield at 20.8Mgha−1, although aboveground nitrogen uptake reached 120kgNha−1. These results are aligned with other reports on this topic showing similarly small optimal nitrogen fertilization rates and a strong capacity to extract soil nitrogen. In a combined analysis of this and three other published studies, crop nitrogen uptake reached approximately 127kgha−1 at the plateau in biomass production (19.7Mgha−1) with a slope of 0.13Mgkg−1. Sustainable management plans for sweet sorghum should include strategies to replenish the often considerable soil nitrogen removed by the crop.

Uptake of fertilizer nitrogen and soil nitrogen by rice using15N-labelled nitrogen fertilizer

Data from five field experiments using labelled nitrogen fertilizer were used to determine the relative effects of soil nitrogen and fertilizer nitrogen on rice yield. Yield of grain was closely correlated with total aboveground nitrogen uptake (soil+fertilizer), less closely correlated with soil nitrogen uptake and not significantly correlated with fertilizer nitrogen uptake. When yield increase rather than yield was correlated with fertilizer nitrogen uptake, the correlation coefficient was statistically significant.