Nitrogen Uptake Efficiency of Olive Cultivars

Maximizing nitrogen uptake efficiency is a sustainable objective to reduce the amount of nitrogen fertilizers applied in olive orchards. Many factors affect this parameter, but nothing is known about whether there are differences among cultivars related to nitrogen uptake efficiency in the olive, and if there are interactions with soil type. To clarify these questions, two groups of experiments were conducted. In the first group, four experiments were carried out in which 20 olive cultivars were compared. In the second group, three experiments were carried out to study the interaction with the type of soil. In all experiments, mist-rooted olive cuttings were growing in 1.1 L pots containing a mixture of sand and peat (2:1 by volume). Depending on the experiment, plants were placed in a shadehouse or in growth chambers at 25/15 °C (day/night) with a 14 h photoperiod and 70% humidity. Plants received weekly applications of 100 ppm N throughout the irrigation water, alternating with one or two applications of 150 mL of tap water. Some plants of each cultivar did not receive nitrogen and served as a control for NUE calculation. A nutrient solution without nitrogen was applied every four weeks to prevent nutritional deficiencies. Results indicated that there are differences among cultivars in the efficiency of uptake nitrogen. The Spanish cultivars ‘Picual’, ‘Arbequina’ and ‘Manzanilla de Sevilla’, together with the Greek cultivar ‘Koroneiki’ and the Italian ‘Frantoio’, were the cultivars with high NUE in this work. Soil type did not affect NUE, and no interaction between soil type and cultivar was observed.

Nitrogen Uptake Efficiency, Mediated by Fine Root Growth, Early Determines Temporal and Genotypic Variations in Nitrogen Use Efficiency of Winter Oilseed Rape

Maintaining seed yield under low N inputs is a major issue for breeding, which requires thoroughly exploiting the genetic diversity of processes related to Nitrogen Use Efficiency (NUE). However, dynamic analysis of processes underlying genotypic variations in NUE in response to N availability from sowing to harvest are scarce, particularly at the whole-plant scale. This study aimed to dynamically decipher the contributions of Nitrogen Uptake Efficiency (NUpE) and Nitrogen Utilization Efficiency (NUtE) to NUE and to identify traits underlying NUpE genetic variability throughout the growth cycle of rapeseed. Three experiments were conducted under field-like conditions to evaluate seven genotypes under two N conditions. We developed NUE_DM (ratio of total plant biomass to the amount of N available) as a new proxy of NUE at harvest, valid to discriminate genotypes from the end of inflorescence emergence, and N conditions as early as the beginning of stem elongation. During autumn growth, NUpE explained up to 100% of variations in NUE_DM, validating the major role of NUpE in NUE shaping. During this period, under low N conditions, up to 53% of the plant nitrogen was absorbed and NUpE genetic variability resulted not from differences in Specific N Uptake but in fine-root growth. NUtE mainly contributed to NUE_DM genotypic variation during the reproductive phase under high-N conditions, but NUpE contribution still accounted for 50–75% after flowering. Our study highlights for the first time NUpE and fine-root growth as important processes to optimize NUE, which opens new prospects for breeding.

The Nutritional Value of Shrimp Waste and Its Response to Growth and N Uptake Efficiency by Corn

Today’s agricultural development is expected to be able to optimize the utilization of agricultural waste resources to improve soil fertility and nutrient for plants, such as the utilization of shrimp waste. This research was conducted to test the level of improvement of the soil fertility and the efficiency of N uptake of corn by application of shrimp waste. The study was conducted using a randomized block design, consisting of five treatments divided as control and the addition of biochar, shrimp waste, urea, and biochar+shrimp waste. Analysis using orthogonal contrast with biochar and shrimp waste was classified as ameliorant, while urea, and biochar+S as fertilizer. The results showed that the application of biochar+S was able to increase soil pH (4.9 out of 4.3), N-total is 85%, OC is 66.2%, CEC is 1.5 times the initial CEC, plant height and number of leaves at 56 days respectively 225 cm and 13 sheets, and Nitrogen uptake efficiency around 24,8% with a dry shell yield of around 10.6 t ha−1. Biochar and biochar+S both increased P-available (4.8 out of 3.4 mg kg−1), whereas K-available increased in shrimp waste applications (88 of 46.1 mg kg−1)

Physiological and molecular interventions for improving nitrogen-use efficiency in maize.

This chapter discusses (i) the importance of nitrogen in plant growth and development, (ii) what is nitrogen-use efficiency (NUE) and how to manage it, (iii) traits influencing nitrogen-uptake efficiency including root system architecture, root nitrogen transporter system, and interaction with microorganisms, (iv) traits influencing nitrogen-utilization efficiency, such as nitrate assimilation, canopy photosynthesis per unit of nitrogen, (v) identification and use of quantitative trait loci (QTLs) related to NUE, (vi) identification of nitrogen-responsive genes, and (vii) nitrogen signalling and transduction for improving NUE. Intensive research on molecular and genetic aspects of NUE has led to the identification of many new genes, QTLs and alleles that could be deployed to develop new genotypes. The future direction of the research efforts should be towards understanding the interaction of NUE-related genes with cellular small RNA flux and perturbing the system performance through metabolic engineering and genome editing techniques.

Strobilurin Effects on Nitrogen Use Efficiency for the Yield and Protein in Durum Wheat Grown Under Rainfed Mediterranean Conditions

In wheat, the increase in nitrogen use efficiency (NUE) and optimization of the nitrogen doses to be used are both very important aspects for improving sustainable and productive agriculture. The aim of this study was to investigate, under rainfed Mediterranean conditions, the influence of strobilurin treatment and N fertilization on durum wheat N use efficiency for yield (NUEy) and protein (NUEp) and on the contribution of their components, nitrogen uptake efficiency (UPE) and nitrogen utilization efficiency (NUtE). Two durum wheat cultivars (Saragolla and Sfinge) were grown for two years in field conditions under five nitrogen treatments (60 kg ha−1 N60; 90 and 120 kg ha−1 given two and three times; N90, N90T3, N120 and N120T3) comparing a control without strobilurin treatment (ST0) and one application of strobilurin (STaz). In Sfinge, STaz caused a decrease in UPE and NUEp and an increase in NUtE and NUEy. In Saragolla, the opposite behavior was observed. Moreover, strobilurin positively affected the contribution of UPE and negatively that of NUtE to NUEy only in Saragolla. Furthermore, strobilurin determined higher NUEy and NUEp values under most of the N treatments adopted in the drier year. With this study, we supported the hypothesis that in Mediterranean conditions, the possibility of reducing N rate application from 120 to 90 kg ha−1 with a strobilurin-based treatment, even in the absence of fungal diseases, could represent a useful agronomic strategy for durum wheat grown under drought conditions as those predicted under the ongoing climate change.