During leaf senescence, essential nutrients are remobilized to sink tissues such as developing seeds and grains. Nutritional contents in the grains of crop plants may be influenced by the extent of the nutrient remobilization process, which may be influenced by the leaf senescence programming. To test these hypothetical relationships in rice plants, nutrient remobilization characteristics of three macro-elements—nitrogen (N), phosphorus (P), and potassium (K)—were examined among ten rice genetic backgrounds including nine representative Thai rice varieties and one Indian variety. Greenness colorations and the N, P, and K contents of flag leaves of the field-grown rice plants were quantified at 0, 7, 14, 21, and 28 days after flowering. Rice varieties that exhibited a stay-green trait or high nutrient remobilization efficiency were identified. On average, the N, P, and K remobilization efficiencies were 50%, 27%, and 22%, respectively, suggesting a poor remobilization process in rice compared to other crop plants. No significant relationship (P < 0.05) was found between the nutrient remobilization rates or efficiencies and the leaf greenness reduction efficiencies among the rice varieties. Furthermore, no significant relationship (P < 0.05) was found between the N, P, and K contents in mature rice grains and the nutrient remobilization rates and efficiencies, or the initial nutrient content stored in flag leaves. Further studies using a larger number and broader range of rice varieties and examining other characteristics of the leaf senescence and nutrient remobilization processes may be needed to verify this lack of association.

During leaf senescence, essential nutrients are remobilized to sink tissues such as developing seeds and grains. Nutritional contents in the grains of crop plants may be influenced by the extent of the nutrient remobilization process, which may be influenced by the leaf senescence programming. To test these hypothetical relationships in rice plants, nutrient remobilization characteristics of three macro-elements—nitrogen (N), phosphorus (P), and potassium (K)—were examined among ten rice genetic backgrounds including nine representative Thai rice varieties and one Indian variety. Greenness colorations and the N, P, and K contents of flag leaves of the field-grown rice plants were quantified at 0, 7, 14, 21, and 28 days after flowering. Rice varieties that exhibited a stay-green trait or high nutrient remobilization efficiency were identified. On average, the N, P, and K remobilization efficiencies were 50%, 27%, and 22%, respectively, suggesting a poor remobilization process in rice compared to other crop plants. No significant relationship (P < 0.05) was found between the nutrient remobilization rates or efficiencies and the leaf greenness reduction efficiencies among the rice varieties. Furthermore, no significant relationship (P < 0.05) was found between the N, P, and K contents in mature rice grains and the nutrient remobilization rates and efficiencies, or the initial nutrient content stored in flag leaves. Further studies using a larger number and broader range of rice varieties and examining other characteristics of the leaf senescence and nutrient remobilization processes may be needed to verify this lack of association.

The focus of this study was to evaluate the effect of varieties on structural, physicochemical, and nutritional characteristics of cool-season adapted chickpeas as an alternative source for protein and energy feed for ruminant livestock. The hypothesis of this study was that cool-season adapted CDC chickpeas varieties grown in Western Canada would have significant differences in nutritional characteristics and truly nutrient supply to dairy livestock. The Crop Development Center (CDC) at the University of Saskatchewan (Saskatoon, Canada) provided the experimental samples of cool-season adapted chickpeas used in this study. Three chickpea varieties, CDC Alma, CDC Cory, and CDC Frontier were collected from three locations in Saskatchewan: Elorse, Limerick, and Lucky Lake. The standard official methods from the Association of Official Analytical Chemists (AOAC) were used for chemical analyses. Energy parameters were determined using the NRC dairy-2001. An in situ technique in cannulated cows was used to evaluate rumen degradation kinetics. Intestinal digestibility was determined in vitro using the 12 h residual samples from in situ incubations. A randomized complete block design (RCBD) with variety as a fixed effect and location as a random effect was used for statistical analyses using the MIXED model procedure of SAS 9.4. Significance was declared at P < 0.05 and tendencies at 0.05 < P < 0.10. Varieties CDC Alma and CDC Cory had a higher carbohydrate content than CDC Frontier (P = 0.02). Conversely, CDC Frontier had higher crude protein (CP) (P = 0.02) and SCP (soluble crude protein) (P = 0.02) than the other chickpeas. The rumen undegraded crude protein (RUP) was higher in CDC Alma and CDC Frontier compared to CDC Cory (P = 0.01). The intestinal digested crude protein (IDP) was higher in CDC Frontier than CDC Alma and CDC Cory (P = 0.03). No differences were observed in the true protein supply (DVE value), metabolizable protein (MP), and Feed Milk Value (FMV) between the three CDC varieties (P > 0.05). In conclusion, the chemical and nutrient profiles, rumen degradation kinetics, intestinal digestibility, and true nutrient availability in lactating cows among the cool-season adapted CDC chickpea varieties have been obtained. The cool-season adapted CDC chickpea varieties had > 770 g/kg EDCP and < 230 g/kg RUCP. CDC Frontier showed better results with relatively higher CP, higher degraded protein balance (OEB, DPB), higher truly digestive protein nutrient supply (DVE, MP) to dairy cows, and higher FMV than other two varieties. In general, cool-season CDC chickpea varieties grown in western Canada can be used as an alternative energy and protein nutrient option for ruminants.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg. | Most arable soils in sub–Saharan Africa savanna and grassland ecosystems are acidic and nutrient deficient with nitrogen and phosphorus being the most limiting and this poses a huge threat to agricultural productivity. To overcome soil nutrient deficiency and increase crop yields, farmers have resorted to high inputs of synthetic fertilizers, which are expensive and may cause environmental degradation. Use of legumes is an important alternative as they help enhance soil nutrition through biological nitrogen fixation. Vigna unguiculata L. (Walp), a highly nutritious legume crop that could be incorporated in small scale cropping systems to improve soil nutrition. However, there is limited information on the physiological and biochemical strategies enabling the growth of V. unguiculata under acidic and nutrient stress conditions. In this study it was hypothesized that symbiotic association between V. unguiculata and rhizospheric microbes affects the growth, nutrient assimilation and phytochemicals of the grain legume grown in nutrient stressed soils. Firstly, this study evaluated the physicochemical properties, microbial composition and soil enzymes activities of soils from four geographically distinct regions of KwaZulu-Natal representing savanna and grassland ecosystems. Secondly, the study investigated how the tripartite symbiosis of V. unguiculata, arbuscular mycorrhizal fungi and nodulating bacteria affect phosphorus and nitrogen nutrition, and the growth of V. unguiculata grown under acidic and nutrient stress conditions. Then, the study investigated how four V. unguiculata varieties regulated their phenolic acids and antioxidants to enhance their growth in acidic and nutrient stressed soils conditions. The four soil types were acidic with low mineral nutrients, with Bergville being the most acidic. The soils were significantly different in their physicochemical and microbial composition. Most bacterial strains identified in the soils belonged to genera Lysinibacillus, and Bacillus while the most identified fungal strains belonged to Fusarium and Trichoderma genera. There were variations in soil lignin degrading, C, N and P cycling enzyme activities. The identified soil enzymes included β-D Phosphatase, L-asparaginase, β-glucosaminidase, β-cellobioside, catalase and lacasse. The availability of this rich pool of soil microbes and soil enzymes is a great opportunity as these can be used to regulate nutrient cycling and enhance nutrient availability for crop production in the savanna and grassland ecosystems. Four V. unguiculata varieties (IT18, Batch white, Brown mix, Dr Saunders) were grown in these acidic and nutrient poor soils. These V. unguiculata varieties were nodulated by several bacterial strains including those of genera Bradyrhizobium, Rhizobium, Bacillus and Paenibacillus. The V. unguiculata fixed more than 60% of its total nitrogen from the atmosphere across all soil treatments. Interestingly, V. unguiculata plants which were nodulated by non-rhizobial bacteria strains effectively fixed significantly high amounts of atmospheric nitrogen. Vigna unguiculata also developed symbiotic association with arbuscular mycorrhizal fungi (AMF) as evidenced by high root mycorrhizal fungi colonization ranging from 58-100%. Variations were observed on growth kinetics, nutrient assimilation and utilization among the four V. unguiculata varieties. Vigna unguiculata was able to switch N source preferences utilizing both soil and atmospheric nitrogen. These findings revealed that V. unguiculata has the capacity to adapt to nutrient poor ecosystems by establishing symbiotic interaction with naturally occurring soil bacteria and AMF and through its ability to switch N source preferences; by using soil N and atmospheric N2 through biological nitrogen fixation. There were variations in the response of the four V. unguiculata varieties to different levels of soil acidity and nutrient stress with regards to phenolic acid concentration and antioxidant capacities. The most abundant phenolic acids were vanillic acid and protocatechuic acid and these constituted 22.59% and 17.22% respectively of the total phenolic acids in the plants. More so, there were differences in correlations between the phenolic acids and plant biomass, plant nutrition, soil nutrition and AMF infection. There was negative correlation between phenolic acids protocatechuic acid and syringic acid, and concentration of plant nutrients N and P. Varieties IT18 and Batch white had relatively lower concentrations of phenolic acids but these had the highest plant biomass. These results confirm that low phenolic acid concentrations have stimulatory effects on growth and nutrient uptake by plants while high concentrations may inhibit plant growth and development. There were variations among the V. unguiculata varieties with respect to oxygen radical absorbance capacity (ORAC) across the four soil types. Overall, the study demonstrated that V. unguiculata is adaptable to acidic and nutrient poor ecosystems as it has the capacity to regulate its phenolic acids which enhance nutrient uptake, promote legume-microbe symbiosis, and help scavenge radical oxidative species due to their antioxidant properties.

Due to an extreme increase in population growth, Egypt suffers from a widening gap in the quantity of imported wheat compared with production and local consumption. Two field trials were conducted during the 2018/2019 and 2019/2020 seasons with three levels of humic substances (HSs) as a foliar spray (1.0, 2.0 and 4.0 g L⁻¹; HS₁, HS₂ and HS₃) and three levels (5.04, 7.56 and 10.08 kg ha⁻¹; HS₄, HS₅ and HS₆) as a soil application. These were applied three times (30, 45 and 60 days after sowing) in comparison with the control (HS₀) to evaluate the performance of three wheat varieties (Seds1 (V₁), Misr2 (V₂) and Giza168 (V₃)) grown in clay loam soil. The experiment was set up according to the split-plot structure in a randomized complete block design; however, the varieties were set as the main plot and treatments were a sub-main plot. Generally, the data indicated that the soil application treatments recorded maximum values for most growth and yield attributes, except for spike length and grain weight per spike, SPAD reading and total grain yield in the first season, and leaf area and biological yield in the second season. HS_1, HS₂, HS₅, and HS₆ were the superior treatments for most of the nutrient contents studied. Regarding the influence of variety, the results showed that V₃ recorded maximum values for LA, SpL, TGW, TGY and leaf Zn and Cu contents in both seasons; PH, GWS and leaf N content in the first season; and SPAD reading, BY and leaf K, Fe and Mn contents in the second season. V₁ was the superior variety for GWS, BY, leaf K and Mn contents in the 2018/2019 season and PH, GNS in the second season, followed by V₂, which had the greatest values for leaf P contents in both seasons, and SPAD reading, GNS and leaf Fe content in the 2018/2019 season and GWS and leaf N content in the second season.

Crop growth and yield often face sophisticated environmental stresses, especially the low availability of mineral nutrients in soils, such as deficiencies of nitrogen, phosphorus, potassium, and others. Thus, it is of great importance to understand the mechanisms of crop response to mineral nutrient deficiencies, as a basis to contribute to genetic improvement and breeding of crop varieties with high nutrient efficiency for sustainable agriculture. With the advent of large-scale omics approaches, the metabolome based on mass spectrometry has been employed as a powerful and useful technique to dissect the biochemical, molecular, and genetic bases of metabolisms in many crops. Numerous metabolites have been demonstrated to play essential roles in plant growth and cellular stress response to nutrient limitations. Therefore, the purpose of this review was to summarize the recent advances in the dissection of crop metabolism responses to deficiencies of mineral nutrients, as well as the underlying adaptive mechanisms. This review is intended to provide insights into and perspectives on developing crop varieties with high nutrient efficiency through metabolite-based crop improvement.

Leaf analysis is essential for diagnosing nutritional status and guiding fertilizer application. The present study aimed to investigate the appropriate time for leaf sampling and the effect of genotype on olive nutrition. We determined leaf nutrient concentrations of calcium (Ca), iron (Fe), and manganese (Mn) in five Greek (‘Amfissis’, ‘Chondrolia Chalkidikis’, ‘Koroneiki’, ‘Mastoidis’, and ‘Kalamon’) and one Spanish (‘Picual’) variety from May 2019 to April 2020. The concentrations of Ca, Fe, and Mn were significantly affected by genotype and season. The highest concentrations for all nutrients were determined in April, while the lowest were in May, June, and October. Leaf Ca concentration significantly increased progressively from May to September for all the varieties. Leaves of ‘Koroneiki’ had the highest Ca concentration. Iron concentrations were within the sufficiency thresholds for all the varieties during the whole experimental period, and ‘Mastoidis’ showed the highest concentration. Leaf Mn concentration for all the varieties increased from May to September with an instant decrease in June, apart from ‘Amfissis’. The varieties ‘Kalamon’ and ‘Chondrolia Chalkidikis’ were found to be above the Mn sufficiency threshold throughout the year. Variations among season and genotype depict the complexity of nutrient transportation in leaf tissues.

The study aimed to examine the effects of PGPR and chemical fertilizer inoculation on the growth, yield, and grain nutrient uptake of teff varieties. For this, two varieties were sown in plots (size: 2´2m each) arranged with factorial (4´2) in a CRBD. Two types of chemical fertilizer and three strains of PGPR either alone or in a consortium inoculated onto two teff varieties. The results of the variance analysis showed that panicle length, the number of total spikelets, shoot dry biomass, grain yield, straw yield, harvest index, grain nitrogen, and phosphorus uptake were highly significant (P&lt; 0.001) for the treatment while panicle length, shoot dry biomass, grain yield, lodging index, and grain iron uptake were also significant (P&lt; 0.00) for teff variety. The interaction effect of the two factors did not significantly affect teff varieties' agronomic traits and grain nutrient uptake. Treatment means comparison results revealed that plant height and lodging index were significantly influenced by the application of 100% recommended dose of chemical fertilizer. The maximum plant height (143.6cm) and lodging index (75%) were observed on Dz-01-196. Panicle length, number of total spikelets, harvest index, and grain yield were significantly affected by the inoculation of the PGPR consortium along with the 50 % recommended dose of chemical fertilizer. The maximum panicle length (55.3cm), number of total spikelets (31.8cm), harvest index (30%), and grain yield (3.6t/h) were recorded on Dz-01-974, which increases up to 529% and 120% over treatment receiving 50% and 100% recommended dose of the chemical fertilizer respectively. Application of a native PGPR consortium with a half dose of chemical fertilizer has increased teff varieties yield and yield-related parameters as well as grain nutrient uptake and could save 50% chemical fertilizer

The present experiment was conducted to study residual effect of three maize (Zea mays L.) varieties on oats (Avena sativa L.) (V1: African Tall, V2: J-1006; V3: P-3396) and four nutrient management practices (N0: Control; N1: 100% RDF; N2: 75% RDF + PGPR + Panchagavya spray; N3: 50% RDF + 25% FYM + PGPR + Panchagavya spray) using split plot design. Results showed that residual effect of maize varieties on oats were found to be nonsignificant for different growth attributes and green fodder yield. Nutrient management practices caused significant variations on growth as well as green fodder yield. Significantly better growth in terms of plant height, number of leaves, leaf length, leaf width, stem girth, number of tillers, CGR as well as RGR at both cuts were recorded with application of 75% RDF + PGPR + Panchagavya spray (N2) compared with control (N0) and 100% RDF (N1). The use of 75% RDF + PGPR + Panchagavya spray recorded significantly highest green fodder yield and production efficiency among all nutrient management practices. Our results indicate that integrated use of organic and inorganic nutrient sources (N2) enhances the productivity of fodder oats, besides reducing 25% dose of chemical fertilizers which can sustain the crop productivity.

The present experiment was conducted to study residual effect of three maize (Zea mays L.) varieties on oats (Avena sativa L.) (V1: African Tall, V2: J-1006; V3: P-3396) and four nutrient management practices (N0: Control; N1: 100% RDF; N2: 75% RDF + PGPR + Panchagavya spray; N3: 50% RDF + 25% FYM + PGPR + Panchagavya spray) using split plot design. Results showed that residual effect of maize varieties on oats were found to be nonsignificant for different growth attributes and green fodder yield. Nutrient management practices caused significant variations on growth as well as green fodder yield. Significantly better growth in terms of plant height, number of leaves, leaf length, leaf width, stem girth, number of tillers, CGR as well as RGR at both cuts were recorded with application of 75% RDF + PGPR + Panchagavya spray (N2) compared with control (N0) and 100% RDF (N1). The use of 75% RDF + PGPR + Panchagavya spray recorded significantly highest green fodder yield and production efficiency among all nutrient management practices. Our results indicate that integrated use of organic and inorganic nutrient sources (N2) enhances the productivity of fodder oats, besides reducing 25% dose of chemical fertilizers which can sustain the crop productivity.