consequence of irrigation with wastewater, a reduction of the crop cycles, ranging
from 7 to 10 days, was also observed within these experimental trials, but without
compromising crop qualitative and quantitative performances. This was due to the
high amount of nutrients, especially nitrogen, not removed by depuration processes
in the considered treated wastewaters that were frequently applied to the plants
(2–3 days interval), up to a few days before harvesting.
In this regard, it is well known that treated municipal wastes, if not undergone to
denitrification treatment, contain high quantities of nitrates, ammonia salts, mineral
perphosphates, and macro-elements than conventional water. High nitrogen supply
to the plants, especially close to product harvest, affects crop cycle duration,
delaying the reproductive phase and reducing the vegetative phase. Therefore, the
plants whose crop cycle ends with the reproductive phase (seed production), under
the irrigation with wastewater, tend to lengthen the crop cycle; on the contrary,
species that are harvested before the production of seeds (horticultural crops whose
product is intended for cooked and/or raw consumption), such as fennel, lettuce,
chicory, cucumber, and barter, can reduce their crop cycle [84]. All the qualiquantitative crop response observed within the In.Te.R.R.A research activities
confirm the results of previous studies aimed at evaluating the agricultural reuse of
municipal wastewaters as alternative irrigation water source, carried out in Apulia
region (Southern Italy) [85, 86].
A field experiment carried out by Qaryouti et al. [87] showed the increase of some
cucumber and tomato crop parameters when wastewater from industry rich in
organic matter and nutrients, particularly K, was reused for irrigation. Especially
in cucumber plant the height, fruit yield and average fruit weight, as well as the
tomato leaf area and plant dry weight were even significantly increased due to the
replacement of K-chemical fertilizer by the wastewater. Also Al-Lahham et al. [88]
reported an increase in tomato fruit size and weight when irrigated with reclaimed
domestic wastewater. Any adverse effect on chemical quality of several vegetable
crop fruits, such as okra (Abelmoschus esculentus L.), bean (Phaseolus vulgaris L.),
corn (Zea Mays L.) and sunflower (Helianthus annuus L.) was observed when grey
treated wastewater, characterized by high BOD and COD values, was used for
irrigation [89].
In addition to plant nutrients, wastewaters may contain various potentially toxic
mineral elements (see Sect. 2.2) with harmful effects on human and animal health
[90]. The transfer of heavy metals to plants irrigated with wastewater may cause
accumulation in plant tissues, and in some cases, the content of these metals may
reach phytotoxicity thresholds. Particularly, high concentration of heavy metals can
result in the reduction in marketable crop yield and/or poor quality of marketable
agricultural products [12]. To this regard, Gatta et al. [29] observed heavy metal
contents (Al, Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn, and Mn) of artichoke heads, harvested
after irrigation with secondary and tertiary treated wastewaters, lower than the
international threshold values. They also found low bioaccumulation factors for
the edible part of the artichoke crop and not significant health risks (hazard index
<1.0) to adults and children after the consumption of the artichoke heads.
Wastewater Reuse in Agriculture: Effects on Soil-Plant System Properties
95
from 7 to 10 days, was also observed within these experimental trials, but without
compromising crop qualitative and quantitative performances. This was due to the
high amount of nutrients, especially nitrogen, not removed by depuration processes
in the considered treated wastewaters that were frequently applied to the plants
(2–3 days interval), up to a few days before harvesting.
In this regard, it is well known that treated municipal wastes, if not undergone to
denitrification treatment, contain high quantities of nitrates, ammonia salts, mineral
perphosphates, and macro-elements than conventional water. High nitrogen supply
to the plants, especially close to product harvest, affects crop cycle duration,
delaying the reproductive phase and reducing the vegetative phase. Therefore, the
plants whose crop cycle ends with the reproductive phase (seed production), under
the irrigation with wastewater, tend to lengthen the crop cycle; on the contrary,
species that are harvested before the production of seeds (horticultural crops whose
product is intended for cooked and/or raw consumption), such as fennel, lettuce,
chicory, cucumber, and barter, can reduce their crop cycle [84]. All the qualiquantitative crop response observed within the In.Te.R.R.A research activities
confirm the results of previous studies aimed at evaluating the agricultural reuse of
municipal wastewaters as alternative irrigation water source, carried out in Apulia
region (Southern Italy) [85, 86].
A field experiment carried out by Qaryouti et al. [87] showed the increase of some
cucumber and tomato crop parameters when wastewater from industry rich in
organic matter and nutrients, particularly K, was reused for irrigation. Especially
in cucumber plant the height, fruit yield and average fruit weight, as well as the
tomato leaf area and plant dry weight were even significantly increased due to the
replacement of K-chemical fertilizer by the wastewater. Also Al-Lahham et al. [88]
reported an increase in tomato fruit size and weight when irrigated with reclaimed
domestic wastewater. Any adverse effect on chemical quality of several vegetable
crop fruits, such as okra (Abelmoschus esculentus L.), bean (Phaseolus vulgaris L.),
corn (Zea Mays L.) and sunflower (Helianthus annuus L.) was observed when grey
treated wastewater, characterized by high BOD and COD values, was used for
irrigation [89].
In addition to plant nutrients, wastewaters may contain various potentially toxic
mineral elements (see Sect. 2.2) with harmful effects on human and animal health
[90]. The transfer of heavy metals to plants irrigated with wastewater may cause
accumulation in plant tissues, and in some cases, the content of these metals may
reach phytotoxicity thresholds. Particularly, high concentration of heavy metals can
result in the reduction in marketable crop yield and/or poor quality of marketable
agricultural products [12]. To this regard, Gatta et al. [29] observed heavy metal
contents (Al, Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn, and Mn) of artichoke heads, harvested
after irrigation with secondary and tertiary treated wastewaters, lower than the
international threshold values. They also found low bioaccumulation factors for
the edible part of the artichoke crop and not significant health risks (hazard index
<1.0) to adults and children after the consumption of the artichoke heads.
Wastewater Reuse in Agriculture: Effects on Soil-Plant System Properties
95