الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 173 |  |  |
| | | from | 173 | | |
Abstract
5.1 Research aim and objectives
This research scientific aim was to assess impacts of using NPK nanofertilizers instead of NPK non-nanofertilizers on potatoes quality, productivity, nutrients use efficiency and soil health under field and laboratory conditions. Therefore, a practicable and economically feasible options can be made to the Egyptian farmers for maintaining sustainable agriculture through improved soil health and crop production and quality and increased nutrients use efficiency in potato crop farming systems. The following stipulated objectives were conducted to achieve this aim:
1- To determine the optimum application rates for NPK nanofertilizers compared to recommended levels of NPK non-nanofertilizers for better potatoes growth and crop yield.
2- To investigate the effects of NPK nanofertilizers in various rates compared to recommended levels of NPK non-nanofertilizers on potatoes crop yield and quality.
3- To determine the effects of optimum application rates for NPK nanofertilizers compared to NPK non-nanofertilizers on relative nutrient use efficiency and relative economics of potato cultivation.
4- To study the effects of NPK nanofertilizers in various rates integrated or not with organic fertilizers compared to recommended levels of NPK non-nanofertilizers on soil health and some soil biochemical and biological properties.
5.2 Research Methodology
Field and incubation laboratory studies were achieved for two years in the period from 15 January 2016 to 25 December 2017, at the facilities of Faculty of Agriculture, Minia University. Under field and laboratory conditions, soil health and potatoes crop yield and quality as well as fate and use efficiency of total NPK from non-nanofertilizers (conventional chemical fertilizers) and NPK nanofertilizers applied to clay soil on conjunction or not with organic fertilizers were studied.
5.2.1 Field experiment
Field experiments were conducted for two seasons (2016 and 2017) at Research Farm facilities, Faculty of Agriculture, Minia University, Egypt, in order to study effects of NPK nanofertilizers compared to NPK non-nanofertilizers on yield and yield components of potato crop (Solanum tuberosum L.) and to estimate whether NPK nanofertilizers applied in equivalent or lower rates could replace recommended levels of NPK chemical fertilizers in potato farming systems without retrograde effects upon yield production or quality. Experiments were laid out in a factorial design based on complete randomized block design (CRBD) with eight treatments and three replicates. Impacts of recommended rates of NPK chemical fertilizers (control treatments) compared to NPK nanofertilizers in equivalent or lower rates (100%, 50% and 25%), foliar or soil applied on potato productivity and quality were studied. Under field conditions, potato crop yield and quality as well as fate and use efficiency of total NPK from non-nanofertilizers (conventional chemical fertilizers) and NPK nanofertilizers applied to clay soil were studied.
5.2.2 Incubation experiment
Incubation experiment was conducted to determine temporary impacts of different fertilization systems on some labile soil biochemical and biological properties following potato monocropping under arid conditions. Field experiment followed by soil incubation was conducted at the experimental farm facilities, Faculty of Agriculture, Minia University, Egypt, in order to study effects of different fertilization systems on biochemical and biological soil properties after incubation for 10 days, as sensitive indicators of soil health after monocropping cultivation of potato crop.
5.3 Research conclusions
The following conclusions can be drawn from results and discussions of this experimental research relating to the identification of agronomic benefits and temporal changes in soil health parameters following applying different fertilization systems using NPK nano and non-nanofertilizers to a soil monocropped with potato under arid conditions.
5.3.1 Agronomic benefits
1- Compared with control treatments, plots receiving foliar application of NPK nanofertilizers at 50% or 25% of recommended level showed higher values of economic yield (23.59-ton ha-1), starch rates (79.62%), NPK nutrient use efficiency (67.74, 278.92, 118.54 kg potato/kg nutrient), harvest index (59.24%) and only lower potato nitrate content (1.15 g/kg) as a harmful indicator.
2- Among all treatments, foliar application of NPK nanofertilizers at 50% rate was found to be the most economical treatment as it gave highest potato yield and quality plus highest profit: cost ratio of potato production.
3- This research recommends foliar application of nanofertilizers in potato production to increase production and quality compared to soil applications.
4- Using lower rates of nanofertilizers as foliar application in the present study proved to be an eco-friendly environmental and economic alternative to recommended rates of chemical fertilizers with significant increase in potato productivity and quality.
5- Foliar application of NPK nanofertilizers at equivalent or lower rates of recommended levels of NPK non-nanofertilizers (chemical fertilizers) had produced a beneficial effect on all potato yield and yield parameters compared to control (conventional chemical fertilizers).
6- Significant use impact of nano and non-nanofertilizers was observed on potato yield and yield growth quality parameters for fertilizer foliar application compared to soil addition.
7- Foliar addition of NPK nanofertilizers at lower rates of 25% or 50% was equal or more effective in improving all potato yield and yield parameters than 100% NPK chemical fertilizers under field conditions.
8- In the light of obtained and discussed results, it could be concluded that nanofertilizers played a significant role in sustaining potato productivity and quality and can be completely in lower rates substitute chemical fertilizers.
9- This substitution of conventional NPK chemical fertilizers by using nanofertilizers in lower rates plus organic fertilizers can be useful in reducing overall cultivation costs and avoiding chemical fertilizers environmental hazards and harmful impacts on soil and public health.
5.3.2 Soil health parameters
1- Application of different fertilization systems caused obvious significant temporal changes on SOC, DOC, DON, microbial biomass-C (C-MIC.), -N (N-MIC.), -P (P-MIC.), bacterial and fungi counts and net N mineralization (N-MIN.).
2- Levels of SOC, DOC, N-MIN., microbial biomass-C (C-MIC.), -P (P-MIC.), bacterial and fungi counts and soil respiration (SR) were significantly increased under organic and integrated fertilization systems compared with inorganic nano or non-nano NPK fertilization system.
3- Levels of microbial biomass-N (N-MIC.) and DON were markedly increased under nano or non-nanofertilizers compared to organic or integrated (organic + inorganic) fertilizers.
4- Several ratios of the studied biochemical and microbial indicators namely DOC: DON, C-MIC.: SOC (Q-MIC%.) and C-MIC.: N-MIC. followed an identical trend as relative chemical and biological properties being greatest in organic, integrated and minimal in nano or non-nano NPK chemical fertilizers.
5- By contrast, higher values of metabolic quotient (qCO2) were recorded in nano or non-nanofertilizer treatments.
6- Enzyme activities of dehydrogenase (DH), β-glucosidase (βG) and acid phosphatase (Ac-P) were in the order of organic > integrated > inorganic fertilization systems, while enzyme activity of urease (UR) was in the vice versa order.
7- Results of this research induced significant temporal differences in clay soil biochemical and biological properties on short-term basis under potato monocropping.
8- Integrated fertilization system of NPK non-nano or nanofertilizers with organic fertilizers recorded greater levels of SOC, DOC, N-MIN., microbial biomass-C (C-MIC.), -P (P-MIC.) and SR relative to sole inorganic fertilizers even though applied at lower rates.
In general, this study delivers clear evidence displaying that different fertilization systems significantly induced agronomic benefits and temporal changes in soil biochemical and biological properties and finally the resultant crop quality and soil health of the agricultural lands. Further, using lower rates of NPK nanofertilizers as foliar application proved to be an eco-friendly environmental and economic alternative to recommended rates of essential chemical fertilizers with significant beneficial effect on all potato yield and yield parameters and soil health.