Genotypic Variation in C and N Isotope Discrimination Suggests Local Adaptation of Heart-Leaved Willow

Plants acquire multiple resources from the environment and may need to adjust and/or balance their respective resource-use efficiencies to maximize grow and survival, in a locally adaptive manner. In this study, tissue and whole-plant carbon isotopic composition (δ13C) and C/N ratios provided long-term measures of use efficiencies for water (WUE) and nitrogen (NUE), and a nitrogen isotopic composition (δ15N) based mass balance model was used to estimate traits related to N uptake and assimilation in heart-leaved willow (Salix eriocephala Michx.). In an initial common garden experiment consisting of 34 populations, we found population level variation in δ13C, C/N and δ15N, indicating different patterns in WUE, NUE and N uptake and assimilation. Although there was no relationship between foliar δ13C and C/N ratios among populations, there was a significant negative correlation between these measures across all individuals, implying a genetic and/or plastic trade-off between WUE and NUE not associated with local adaptation. To eliminate any environmental effect, we grew a subset of 21 genotypes hydroponically with nitrate as the sole N-source, and detected significant variation in δ13C, δ15N and C/N ratios. Variation in δ15N was mainly due to genotypic differences in the nitrate efflux/influx ratio (E/I) at the root. Both experiments suggested clinal variation in δ15N (and thus N uptake efficiency) with latitude of origin, which may relate to water availability and could contribute to global patterns in ecosystem δ15N. There was a tendency for genotypes with higher WUE to come from more water replete sites with shorter and cooler growing seasons. We found that δ13C, C/N, and E/I were not inter-correlated, suggesting that selection of growth, WUE, NUE and N uptake efficiency can occur without trade-off.

Effect of Different Levels of Urea Super Granule and Prilled Urea on the Crop Quality, Nutrient Uptake and Soil Nutrient Status of Broccoli

A field experiment was conducted at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during the period 2010-2011 to assess the effect of urea super granule (USG) and prilled urea (PU) on the quality attributes (Compactness coefficient, Vitamin C, β-carotene and chlorophyll contents) of broccoli, to assess the comparative performance of USG and PU on nutrient uptake and uptake efficiency of broccoli plant, to assess the effect of different forms and levels of urea N on the post harvest soil nutrient status of broccoli field and to select the better doses of USG and PU for quality broccoli production in Shallow Red-Brown Terrace Soil under Madhupur Tract (AEZ-28). The experiment was laid out in a randomized complete block design with three replications having 17 treatments constituted with different levels of urea super granule (USG) and prilled urea (PU) as- T1: N-control, T2: PU-N80, T3: PU-N100, T4: PU-N120, T5: PU-N140, T6: PU-N160, T7: PU-N180, T8: PU-N200, T9: PU-N220, T10: USG-N80, T11: USG-N100, T12: USG-N120, T13: USG-N140, T14: USG-N160, T15: USG-N180, T16: USG-N200, T17 and USG-N220 kg ha-1. Results revealed that the comparative performance of USG in relation to head quality (compactness coefficient, ascorbic acid, β-carotene and chlorophyll content), nutrient (NPKS) uptake and N uptake efficiency was found better as compared to PU. The compactness coefficient, β-carotene and chlorophyll contents were increased with increasing rate of N as well as USG and PU, but ascorbic acid content was slightly decreased with increasing rate of USG and PU. The maximum compactness coefficient (18.61) was found from the treatment USG-N180 that was followed by USG-N160 (18.24) and the highest β-carotene content (0.401 mg/100gFW) was found from USG-N160 followed by PU-N180 (0.40 mg/100gFW). Similarly the highest chlorophyll-a content (0.818 mg/100gFW) was found from USG-N180 followed by USG-N160 (0.814 mg/100gFW) and the highest chlorophyll-b content (1.141mg/100g FW) was recorded from USG-N180. The higher nutrient uptake and N uptake efficiency (108.531%) was obtained from USG treated plots over that of the PU. But N uptake efficiency was decreased with increasing rates of N fertilizer. But post harvest soil nitrogen status did not show any systematic trend although it was found higher in USG over PU. Similarly no remarkable changes were observed in post harvest soil P, K, S and B status for the crop. However, USG @ 160 kg N ha-1 (USG-N160) followed by USG-N140 and PU @ 180 kg N ha-1 (PU-N180) with other recommended doses of fertilizer could be suggested as USG and PU based fertilizer recommendation for a good quality broccoli production in terms of yield and quality in Silty Clay Loam Soil of Madhupur Tract.The Agriculturists 2017; 15(2) 24-39

Fertigation Frequency Affects Growth and Water and Nitrogen Use Efficiencies of Swingle Citrumelo Citrus Rootstock Seedlings

We determined if frequency of application of irrigation water plus fertilizer in solution (fertigation) could modify root and shoot growth along with growth per unit nitrogen (N) and water uptake of seedlings of the citrus rootstock Swingle citrumelo growing in a greenhouse. In the first experiment, all plants received the same amount of water with sufficient fertilizer N but in three irrigation frequencies applied in 10 1.5-mL pulses per day, one 15-mL application per day, or 45 mL applied every 3 days. Plants irrigated at the highest frequency grew the least total dry weight and had the highest specific root length. Plants with lowest irrigation frequency grew the most and used the least water so had the highest water use efficiency. There were no irrigation frequency effects on relative growth allocation between shoot and roots, net gas exchange of leaves, or on leaf N. A second experiment used identical biweekly irrigation volumes and fertilizer rates, but water and fertilizer were applied using four frequency combinations: 1) daily fertigation; 2) daily irrigation with fertilizer solution applied every 15 days; 3) fertigation every 3 days; or 4) irrigation every 3 days and fertilizer solution applied every 14 days. Total plant growth was unaffected by treatments, but the highest frequency using the lowest fertilizer concentration grew the greatest root dry weight in the uppermost soil depths. Roots grew less and leaf N was highest when N was applied every 15 days, implying that root N uptake efficiency was increased when fertigated with the highest fertilizer concentration. All plants had similar water use efficiencies. A third experiment was conducted with irrigation every 3 days and with four different N application frequencies: every 3, 6, 12, or 24 days using four fertilizer concentrations but resulting in similar total N amounts every 24 days. There were no differences in growth, gas exchange, or water use efficiency. Given the fact that all treatments received adequate and equal amounts of water and fertilizer, fertigation frequency had only small effects on plant growth, although very high frequency fertigation decreased N uptake efficiency.

Enhancing the Urea-N Use Efficiency in Maize (Zea mays) Cultivation on Acid Soils Amended with Zeolite and TSP

Ammonia loss significantly reduces the urea-N use efficiency in crop production. Efforts to reduce this problem are mostly laboratory oriented. This paper reports the effects of urea amended with triple superphosphate (TSP) and zeolite (Clinoptilolite) on soil pH, nitrate, exchangeable ammonium, dry matter production, N uptake, fresh cob production, and urea-N uptake efficiency in maize (Zea mays) cultivation on an acid soil in actual field conditions. Urea-amended TSP and zeolite treatments and urea only (urea without additives) did not have long-term effect on soil pH and accumulation of soil exchangeable ammonium and nitrate. Treatments with higher amounts of TSP and zeolite significantly increased the dry matter (stem and leaf) production of Swan (test crop). All the treatments had no significant effect on urea-N concentration in the leaf and stem of the test crop. In terms of urea-N uptake in the leaf and stem tissues of Swan, only the treatment with the highest amount of TSP and zeolite significantly increased urea-N uptake in the leaf of the test crop. Irrespective of treatment, fresh cob production was statistically not different. However, all the treatments with additives improved urea-N uptake efficiency compared to urea without additives or amendment. This suggests that urea amended with TSP and zeolite has a potential of reducing ammonia loss from surface-applied urea.

Productivity and nitrogen use efficiency parameters in cotton cultivars with varying N levels and soil types under rainfed conditions

A field experiment was conducted under rainfed conditions, on a shallow soil (Inceptisol) underlain with weathered basalt and on a deep soil (Vertisol) to evaluate three cotton cultivars [AKH 4 ( Gossypium arboreum ), LRK 516 ( G. hirsutum ) and NHH 44 (intra- hirsutum hybrid)] under four levels of N (0, 40, 80 and 120 kg ha −1 ) and to analyse the variations in productivity using the nitrogen use efficiency (NUE) parameter. The yield of AKH4 and NHH 44 was 101 and 89% higher than that of LRK 516. The yield and the response to N were higher on the Inceptisol. The enhanced yield and NUE of AKH 4 and NHH 44 were attributed to the improved efficiency of N uptake utilization. NUE declined from 21.6 at 40 kg ha −1 to 7.7 at 120 kg N ha −1 . The N uptake efficiency and N utilization efficiency were independent of each other, but complemented each other in improving NUE. The implications of variations in NUE, N uptake efficiency and N utilization efficiency and their components, N biomass production efficiency and HI, in cotton breeding and agronomy are also discussed.