154
D. L. N. Rao et al.
3.3.2 Nano-Fertilizers
Nanotechnologies refer to those technologies that contain at least 50% natural or
manufactured particles in the size range from 1 to 100 nm. Nano-based smart
fertilizer delivery systems have the ability to provide more efficient and targeted
delivery to specific plant cells due to their size-related high surface area. Also, they
show enhanced stability in the environment, and slow or controlled release which
improves the availability of nutrients to crops and improves the stress resistance of
crops. The increased use efficiency can reduce the consumption of fertilizers, besides
reducing environmental fallouts. Nano-biosensors can enhance this process even
further by enabling smart delivery systems to precisely release nutrients in response
to environmental triggers such as heat and moisture and nutrient demand signals like
carbonaceous root exudates, thus enabling real-time monitoring and control.
Liu et al. [52] have shown that nano-composites containing organic polymer
intercalated in the layers of kaolinite clays can be used as a cementing material
to regulate the release of nutrients from conventional fertilizers. A patented nanocomposite consisting of N, P, K, micronutrients, mannose and amino acids was shown
to increase the uptake and utilization of nutrients by grain crops [42]. Bansiwal et al.
[5] developed a surface modified zeolite as a carrier of slow release phosphatic
fertilizer. Mukhopadhyay [60] developed patented nano-fertilizers by intercalating
phosphate ions in kaolin clay mineral and zinc-based nanomaterials by using clay
receptacles and embedding into a polymer matrix. Nano-fertilizers are capable of
releasing nutrients, especially NO 3 -N for more than 50 days while nutrient release
from conventional fertilizer (urea) ceased beyond 10–12 days [92]. Application of
nano-P increased the growth rate and seed yield of soybean by 33 and 20% compared
to regular P fertilizer Ca [(H 2 PO 4 ) 2 ] [51]. However, these fertilizer materials need
to be screened for bio-hazards before large-scale adoption under field conditions.
3.4 Fertilizers Influence on Soil Health
Soil acidification following heavy nitrogen application is well known. Guo et al. [34]
reported significant soil pH reductions in large production areas in China; N cycling
released 20–221 kilomoles of hydrogen ion (H
+ ) ha
−1 yr
−1 and base cations uptake
contributed a further 15–20 kilomoles of H
+ ha
−1 yr
−1 to soil acidification in four
widespread cropping systems. However, application of recommended quantities of
fertilizers are beneficial to soil productivity. Ladha et al. [46] analyzed data following
time by fertilizer N response ratio in 114 long-term experiments and found declines
of 7–16% in organic C and 7–11% in organic N with no N amendments. But in soils
receiving fertilizer N, average increase of 8% in organic C and 12% in organic N were
reported. Addition of organic matter (i.e., manure) increased SOM, on average, by
37%. Their results showed that in addition to its role in improving crop productivity,
synthetic fertilizer N significantly reduces the rate at which SOM is declining in
agricultural soils, worldwide. In long-term fertilization trials in cropping systems
D. L. N. Rao et al.
3.3.2 Nano-Fertilizers
Nanotechnologies refer to those technologies that contain at least 50% natural or
manufactured particles in the size range from 1 to 100 nm. Nano-based smart
fertilizer delivery systems have the ability to provide more efficient and targeted
delivery to specific plant cells due to their size-related high surface area. Also, they
show enhanced stability in the environment, and slow or controlled release which
improves the availability of nutrients to crops and improves the stress resistance of
crops. The increased use efficiency can reduce the consumption of fertilizers, besides
reducing environmental fallouts. Nano-biosensors can enhance this process even
further by enabling smart delivery systems to precisely release nutrients in response
to environmental triggers such as heat and moisture and nutrient demand signals like
carbonaceous root exudates, thus enabling real-time monitoring and control.
Liu et al. [52] have shown that nano-composites containing organic polymer
intercalated in the layers of kaolinite clays can be used as a cementing material
to regulate the release of nutrients from conventional fertilizers. A patented nanocomposite consisting of N, P, K, micronutrients, mannose and amino acids was shown
to increase the uptake and utilization of nutrients by grain crops [42]. Bansiwal et al.
[5] developed a surface modified zeolite as a carrier of slow release phosphatic
fertilizer. Mukhopadhyay [60] developed patented nano-fertilizers by intercalating
phosphate ions in kaolin clay mineral and zinc-based nanomaterials by using clay
receptacles and embedding into a polymer matrix. Nano-fertilizers are capable of
releasing nutrients, especially NO 3 -N for more than 50 days while nutrient release
from conventional fertilizer (urea) ceased beyond 10–12 days [92]. Application of
nano-P increased the growth rate and seed yield of soybean by 33 and 20% compared
to regular P fertilizer Ca [(H 2 PO 4 ) 2 ] [51]. However, these fertilizer materials need
to be screened for bio-hazards before large-scale adoption under field conditions.
3.4 Fertilizers Influence on Soil Health
Soil acidification following heavy nitrogen application is well known. Guo et al. [34]
reported significant soil pH reductions in large production areas in China; N cycling
released 20–221 kilomoles of hydrogen ion (H
+ ) ha
−1 yr
−1 and base cations uptake
contributed a further 15–20 kilomoles of H
+ ha
−1 yr
−1 to soil acidification in four
widespread cropping systems. However, application of recommended quantities of
fertilizers are beneficial to soil productivity. Ladha et al. [46] analyzed data following
time by fertilizer N response ratio in 114 long-term experiments and found declines
of 7–16% in organic C and 7–11% in organic N with no N amendments. But in soils
receiving fertilizer N, average increase of 8% in organic C and 12% in organic N were
reported. Addition of organic matter (i.e., manure) increased SOM, on average, by
37%. Their results showed that in addition to its role in improving crop productivity,
synthetic fertilizer N significantly reduces the rate at which SOM is declining in
agricultural soils, worldwide. In long-term fertilization trials in cropping systems