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العنوان
THE EFFECT OF BIOCHAR ON GROWTH AND YIELD OF WHEAT PLANT UNDER DROUGHT CONDITIONS \
المؤلف
NEGM, WESAM MANSOUR AHMED.
هيئة الاعداد
باحث / وسام منصور أحمد نجم
مشرف / محمد عبد الرسول محمد إبراهيم
مشرف / سيد عبد المنعم سيد حسين
مشرف / بهاء بدرى موسى سالم
تاريخ النشر
2019.
عدد الصفحات
185 p. :
اللغة
الإنجليزية
الدرجة
ماجستير
التخصص
علوم النبات
تاريخ الإجازة
21/1/2019
مكان الإجازة
جامعة عين شمس - كلية الزراعة - النبات الزراعى
الفهرس
Only 14 pages are availabe for public view

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from 185

Abstract

Globally, wheat (T. aestivum L.) production is being haunted by several abiotic stresses such as drought, the primary hurdle for sustainable wheat production. Drought stress decreased the wheat productivity by up to 70%, a situation that might be worsened with the forthcoming era of global warming. Improving plant resilience to water scarcity is a great challenge of the green biotechnological revolution to increase food production by 70% to feed the increasing population by the year 2050. Toward this end, sustainable utilization of organic matter inputs such as biochar (BC) has emerged as a feasible win-win strategy to enhance crop productivity and mitigate greenhouse gasses emission. Experimental evidences so far showed that BC soil application could improve plant growth, development and productivity, along with better resistance to various abiotic stresses. However, the effects of BC application on the soil-plant system may vary widely, depending on the soil type, plant species, and biochar properties (in terms of feedstock and pyrolysis conditions).
Hence, this study aimed to evaluate the agronomic potential of locally-produced biochar on the growth, development, productivity as well as drought resistance of wheat plants (cultivar: Giza 168). Biochar used in the present study was produced using a locally manufactured pyrolytic equipment based on Anila Stove design (slow pyrolysis process: 10 kg h-1, at 350 - 500 °C and a conversion rate of 4:1). Feedstock used was different biomass, commonly found in the agricultural wastes of the Faculty of Agriculture, i.e. woodchips (mainly Acacia .sp and Delonix regia), tree-prune and grass clippings. The charred materials were then crushed, screened with 2 mm sieve and air-dried for 48 h prior to use. The physical and chemical analysis of the obtained biochar revealed that it was alkaline, with pH value of 9.64, an EC value of 3.61 dsm-1, bulk density of 256 kg m-3, water content of 18.2% and ash concentration of 16.4%. It contains distinctly high carbon (83.6%), but very low nitrogen concentration (0.56%) concentrations, with C/N ratio reached 149. The obtained biochar showed also the presence of a range of minerals such as P (0.55%), K (1.36%), Fe (1038 mg kg-1), Mn (70 mg kg-1) and Zn (72 mg kg-1).
A completely randomized greenhouse pot experiment (two successive agricultural seasons during 2014/2015 and 2015/2016) was conducted to investigate the influence of different BC application rates (0, 2 and 5%) on the growth, development and productivity of wheat plants grown under different water regimes (60, 30 and 15% WHC), for a total period of 18 weeks. The pots were kept in an open field greenhouse (wirehouse) under ambient conditions with temperatures of 20±3 ºC daytime and 14±3.5 ºC night time, a photoperiod of 10/14 h, relative humidity of 60-70% and light intensity of 1500 - 2000 µmol m-2 s-1. Two successive samples were taken to evaluate the effect of biochar soil-amendment on wheat growth, development and productivity. The first one (vegetative) was at the booting stage (60 days after sowing), while the second sample (yield) was after ripening (165 days after sowing). Plant responses (morphological and physiological) to different levels of biochar soil application under various soil water contents were evaluated by assessing several growth-related parameters (fresh and dry weights, plant height, tillers number, leaf number, area, and mass to area ratio, and shoot: root fresh weight ratio), water relations (water content, leaf relative water content and osmotic potentials), membrane stability, photosynthetic pigments and composition of minerals and compatible solutes in different plant parts. At the harvest time, several yield attributes such as spike number, length and weight, grain yield and weight of 1000 grains were also evaluated. All these scientific data were correlated and used to get precise insights about the effectiveness of biochar soil application on wheat plants and the underlying mechanisms behind its effects. Drought stress negatively impacted the growth and development of wheat plants, with severe effects at the lowest soil water content treatment. Plants exposed to drought were distinctly thin, with less number of tillers and leaves. The leaves were also smaller and appeared dark-green in color, particularly at moderate drought stress treatment. Under severe drought stress, the leaves became yellow, with some signs of nutrition disorder and senescence compared to those of the control plants. Overall, most growth-related parameters measured in this study were negatively affected in response to water stress, the effect that was more pronounced under severe water stress. Drought stress decreased the total plant biomass by 65% and 72% at moderate and severe drought stress, respectively, compared to well-watered controls. The number of tillers per plant was significantly reduced by 66% and 73%, and that of the leaves by 58% and 74% in plants grown at 30% and 15% WHC, respectively, compared to well-watered controls. Surface leaf area per leaf was also reduced, being only 62% and 56% of that of the controls at moderate and severe drought stress, respectively. Drought-induced growth reduction was associated with an impaired plant water balance (indicated by lower LRWC and ψs), ion imbalance (indicated by reduced K+, relatively lower N and higher Mg2+ and Ca2+ concentrations), reduced photosynthetic pigments, enhanced LEL and higher proline concentrations in both the root and shoot tissues. Water stress distinctly abridged all yield-contributing parameters (spike number, length and weight per spike), leading consequently to reduce the grain yield per plant. Spike number per plant was significantly lowered, reached about 63% and 52% of the control values at moderate and severe drought treatments, respectively. Similarly, the spike length was decreased by 7% and 27% for plants exposed to moderate and severe water deficit, respectively. Spike weight was also reduced by 10% and 23% upon exposure to moderate and severe water stress, respectively. Consequently, the grain yield per plant was progressively decreased by 70% and 97% at moderate and severe water stress, respectively, compared to well-watered controls.
Soil applied BC at either 2% or 5% substantially improved wheat growth and productivity, both under sufficient and limited water supply. At ample water regime, BC resulted in substantial increases of about 183% and 100% in total plant biomass when applied at 2% and 5%, respectively compared to non-amended controls. BC-induced improvements in plant biomass were coincided with significant increases in plant height and numbers of tillers and leaves per plant. Furthermore, the leaves BC-treated plants were light green, with higher surface area, and remained active and juvenile for longer time, compared with the corresponding un-amended controls. Most interestingly, BC-treated wheat plants showed conspicuous growth even under severe drought stress conditions, confirming the potential of BC in enhancing plant drought resistance. BC applied at 2% increased the plant biomass by up to 400% and 80% at moderate and severe water stress treatments, respectively, compared to un-amended controls. The same trend was also noted, but to a lesser extent, when BC was applied 5% BC. It led to increase the plant fresh weight by 220% and 58% at moderate and severe drought stress treatment, respectively, compared to un-amended controls. The beneficial effects of adding BC were also manifested by 137% and 107% increases in the grain yield (GYPP), when BC was applied at 2% or 5%, respectively, under normal irrigation treatment. The interactive effect of drought and BC treatments was highly significant, as BC application at 2 and 5% increased the GYPP by roughly 317% and 308%, respectively, for plants exposed to moderate water stress. Under severe drought, BC applied at 2 and 5% caused up to 6.7 and 1.6 folds increases in the GYPP, respectively, relative to the respective controls. BC-induced improvement in the GYPP was attributed to a higher spike number per plant (SNPP), a higher spike length (SL), a higher spike weight per spike (SWPS) as well as a higher 1000-grain weight. Taken together, these results suggest that 2% BC could be considered as an optimal level of BC application to sustain wheat growth and productivity, at least under our experimental conditions, both under ample and limited water supply.
It is conceivable that BC-mediated growth stimulation observed in this study is linked to its positive effects on the physical and chemical properties of the soil (an improved soil WHC, and nutrient concentrations). This ultimately contributed to an improved plant water status (higher ψs and LRWC) as well as a better plant nutrient uptake (mainly, K+, Mg2+ and N concentrations). These responses were subsequently translated into more vigorous plant growth, higher grain yield as well as a higher degree of drought resistance. Hence, drought-induced disorders in plant growth, physiology and hence productivity of wheat could be ameliorated by BC soil application, with 2% BC was most effective, particularly at severe drought stress. from a practical point of view, this study justifies the potentials of biochar as a novel approach for improving crops productivity and could be considered as a step forward for its use to sustain crop production, particularly, at marginal areas of Egypt. However, more focused and process oriented field studies under prevailing conditions of limited water are needed to evaluate the full potentials of biochar in enhancing stress resistance in wheat plants, since several responses underlying drought resistance may be overlooked when operating outside the field context.