The purpose of this presentation is to explain how a forthcoming publication on fertilizer use and human health contributes to the sustainability initiatives of the fertilizer industry.
Our Institute is supported by primary producers of plant nutrients, and our mission is to develop and promote scientific information about management of plant nutrition for the benefit of the human family.
My talk today is structured around Fertilizer Use and Human Health, the topic of an upcoming scientific review publication that IFA and IPNI have been developing. The objective is to describe how fertilizers contribute to food and nutrient security for the health of a growing global population. The editorial committee includes Patrick Heffer of IFA, myself, Kevin Moran of Yara, Ismail Cakmak with Sabanci University, and Ross Welch from Cornell University. Release – intent is spring 2011.
There’s always a risk in attempting to do balanced reviews of science. Adversaries may take it as concession. But the majority of our supporters in the science world appreciate our efforts to be forthright about adopting a credible evidence-based approach. The intent is to inform our industry. To raise awareness of the positive impacts of fertilizer use, our communicators must be aware of the negatives, and our communications pieces must be based on science. The intent is to correct misperceptions. There are many oft-repeated mantras in the sciences of human nutrition, medicine, and ecology that simply are not supported by evidence, and this needs to be pointed out. The intent is also to invite constructive contributions toward resolving the issues that exist – and the industry’s 4R Nutrient Stewardship approach allows that to happen in a manner that balances the benefits and the risks. Who is the intended audience? Our intent would be a wide distribution among those with serious interests in engaging the issue of sustainability. It would include scientists, educators and policymakers dealing with fertilizer, agriculture and the food chain. It would include academia and students, with the hope that a positive impression of the industry’s commitment to product stewardship would be evident.
A few key points from each chapter (not complete coverage of each topic) Covering the positives and the challenges We desire a good image as the industry that “feeds the world.” What strategies do we need to employ to earn and maintain that image? Some issues could be considered more positive than others – but really all hold both challenges and opportunities for the industry.
“ The yield gains brought about by the Green Revolution through the use of improved cultivars, fertilization, irrigation, and mechanization seem to have been achieved at the expense of essential nutrient and phytonutrient contents (Davis, 2009)” “ Mozafar (1993) noted that the concentrations of carotenes and vitamin B 1 tend to increase with N fertilization whereas the concentration of vitamin C decreases. Recent studies have also confirmed these trends . For instance, lycopene and beta-carotene contents in peppers were increased by nearly 50% and 20% respectively in response to fertilization with NO 3 -N (Flores et al., 2004). Barickman et al. (2009) have also reported positive correlations between N supply amount and concentrations of antioxidant carotenoids (beta-carotene, lutein, neoxanthin and zeaxanthin) in watercress ( Nasturtium officinal R. Br.). Similarly, Kopsell et al. (2007a) found linear increases in carotenoid concentrations (lutein, beta-carotene and chlorophyll pigments on a dry mass basis) in leaf tissues of kale in response to N fertilization. Lutein and beta-carotene are potent antioxidant pigments and play an important role in eye health. Together with vitamins A, C and E, they can help lower the risk of developing, or slow down the progression of age-related macular degeneration (AMD), which is one of the leading causes of blindness” “ increasing the NO 3 :NH 4 ratio in fertilizer solutions resulted in significant increases in both the dry and fresh mass concentrations of lutein and beta-carotene in kale leaves” “ High N fertilization rates have also been associated with reductions in the concentrations of naringin and rutinoside in grapefruits (Patil and Alva, 1999; 2002), anthocyanin in apples (Awad and Jager, 2002), and polyphenolic compounds and antioxidant activity in basil (Nguyen and Niemeyer, 2008)” “ Inverse associations between potassium intake and the incidence of cardiovascular diseases such as stroke and coronary heart disease have been reported (He and MacGregor, 2008)” “ Foliar K treatments increased tissue K concentrations, fruit sugars and bioactive compounds (ascorbic acid and β-carotene) by 19%, 21% and 15%, respectively, even though soil K levels were high” “ In pink grapefruit, supplemental foliar K resulted in increased lycopene, beta-carotene, and vitamin C concentrations (Patil, 2002), however, higher levels of soil-applied K resulted in lower fruit total ascorbic acid levels (Patil and Alva, 2002) ”
Figure 2: Effect of nitrogen fertilization on yield and protein content of Katepwa hard red spring wheat (Grant, unpublished) “ In rice, protein occupies the spaces between starch granules. application of N to increase protein content can reduce breakage.” “ in a study with 31 cultivars of rice in Nanjing China, both the average total protein content and the protein quality, in terms of glutelin/total protein increased with increasing N level (Ning et al., 2009). Glutelin has a higher proportion of lysine than does prolamin. Nitrogen fertilizer also decreased the concentrations of phytic acid, an anti-nutritional factor that decreases the bioavailability of both protein and trace elements ” “ Miao et al. (2007) found that the N rate to maximize corn grain protein concentration was 45 to 50 kg ha-1 higher than the optimal rate for yield., but VRN did not reduce variability in protein. ” Increasing N increased the proportion of zein in corn protein, decreasing lysine and tryptophan, except in opaque-2 QPM – also reflected in biological value in rat feeding experiments. “ Increases in [wheat] protein content due to N fertilization may not improve the nutritional value of the grain to the same extent because of the proportionally higher increase in the lysine-poor gluten proteins (Shewry, 2009). ”
Rice – carbohydrate – “Overall, grain quality was less responsive to N than crop yield, showing trends of higher chalkiness and worse eating/cooking quality at higher than moderate or low N levels. Quality may be improved by increasing the proportion of N applied after panicle initiation, to improve milling quality, appearance and protein content (Yang et al., 2007). ” Maize – “ Nitrogen fertilizer increased protein content and test weight and decreased maize oil (Miao et al. 2007) and starch content and extractable starch content (Miao et al. 2007, Singh et al. 2005(Riedell et al., 2009). ” “ In studies conducted in Illinois, shifts in oil content followed the same general pattern as for protein content, increasing with N application (Lang et al., 1956) but effects on oil content were small. ” Wheat – “ Nitrogen fertilizer increased both protein content and Hagberg falling number (Kindred et al., 2005) ” - lower α-amylase activity means a stronger dough. Soybean - “ fertilization with P or dolomite (a magnesium-containing lime) increased both oil and protein along with yield. (Yin and Vyn, 2003).” “Yin and Vyn (2003) reported a slight (from 215 to 218 g/kg) increase in soybean seed oil concentration in response to band (but not broadcast) application of K fertilizer while research in Harrow, Ontario, found increased oil and soluble sugars n response to applied K” Potato – “Eppendorfer and Eggum (1994) reported a comprehensive analysis of potato protein and starch qualities in response to application of mineral fertilizers. While their results were based on outdoor pot studies, making comparison to rates used in field production difficult, they found that nutrient addition levels producing maximum yields generally resulted in high protein and starch levels as well (Table x). They reported that N applied to the soil strongly increased crude protein content of potato, but reduced its biological value. As crude protein increased, the proportion of asparagine increased while that of essential amino acids declined. Nevertheless, the reduction in biological value was smaller than the increase in crude protein, and thus the total production of bioavailable essential amino acids increased with N application, even beyond the rate of application required for maximum yield. Increasing levels of P and K reduced crude protein but increased its biological value. Sulfur deficiency strongly reduced biological value of protein as well, owing to reductions in methionine and cysteine (Eppendorfer and Eggum, 1994).”
Figure 5. Effect of different S fertilization rates on the baking quality of two wheat cultivars as measured by a microscale baking test using 10 g of wholemeal flour. (A) Images of micro bread slices of the cultivar Batis at a comparable scale. (B) Histograms of bread volumes; different letters represent significant differences of the mean values. Error bars represent(standard errors of five independent pot replicates. Statistical significance (p<0.05) is indicated by small letters for the S rates and capitals for the cultivars (Zörb et al., 2009). Sulphur deficiency leads to a change in the composition of protein in wheat. Amounts of S-poor proteins such as ω-gliadins increase and S-rich proteins such as γ-gliadins and low molecular weight subunits of glutenin are reduced by S deficiency (Tea et al., 2007; Tea et al., 2004; Wieser et al., 2004). The reduced proportion of S-rich compounds leads to tough, less extensible dough leading to a lower bread volume even with a similar protein content ( Figure 5 ) (Reinbold et al., 2008; Thomason et al., 2007; Zörb et al., 2009). Similarly, in durum wheat, on a site that was not S-deficient, S application increased the amount of LMWG at the expense of the HMWG (Lerner et al., 2006) .
Nitrate nutrition – a complex and intriguing issue. The traditional view of nitrate as only a risk factor for blue babies and cancer has been recast by discoveries beginning in the 1980s in regard to its physiological role in NO –the nitric oxide pathway. Methemoglobinemia is rare, and the evidence on cancer is inconclusive. The science has note completely removed these risk factors, but today they are counterbalanced by the findings of the beneficial roles of nitrate in the human body, including cardiovascular health and protection against infections. Ingested nitrate often only matches the volume of nitrate cycled internally within the human body. Nitrates in fruits and vegetables – usually the largest ingestion source – are not associated with adverse toxic outcomes – largely because of counterbalancing with vitamins and antioxidants. “ For years, people have viewed dietary sources of nitrate, including drinking water, as harmful to humans causing methemoglobinemia and cancers. However, methemoglobinemia is rare and evidence suggests a relation with infective enteritis rather than with nitrate alone. Also epidemiological evidence for an association between cancers of the digestive tract and nitrate intake is inconclusive in terms of increased risks of cancer. The discovery of the nitric oxide pathway in the early 1980s revealed that nitrate is actually produced endogenously in the body changing our perception of nitrate safety. Recently benefits of dietary sources of nitrate for cardiovascular health and protection against infections have been unveiled” Negative health impacts of chronic exposure to high nitrate in drinking water – are uncertain, and occur in susceptible sub-populations – those with low vitamin C intake, high meat intake, and a history of bowel inflammation. “ It is hard to conceive that the ingestion of nitrate from fruits and vegetables could have any impact on potential adverse toxic outcomes.” “ Although health risks and social cost of nitrate in drinking water are small they may justify adjustment of agricultural practices, as there is quite some scope for cost-efficient reduction of nitrate runoff”
“ Townsend et al. (2003) hypothesized that increasing nutrient availability may often favor disease-causing organisms.” Even though many questions remain regarding the linkages between eutrophication and harmful algal blooms, and regarding the degree to which agricultural nutrients are responsible, it must be acknowledged that the perturbations arising from the globally unprecedented, large-scale increase in the use of fertilizer in the past 50 to 100 years are worthy of careful attention and study. Those engaged in research and development of agricultural crop production recognize the multiple benefits of increasing nutrient use efficiency, and have already made considerable progress in reducing nutrient surpluses and nutrient losses. Continued progress is needed to ensure optimum human health on both sides of the equation: the provision of adequate quantities of nutritious food, and the avoidance of harm to the environment upon which all life depends.
“ Townsend et al. (2003) hypothesized that increasing nutrient availability may often favor disease-causing organisms.” Townsend et al. 2003: “Ecological feedbacks to excess nitrogen can inhibit crop growth, increase allergenic pollen production, and potentially affect the dynamics of several vector-borne diseases, including West Nile virus, malaria, and cholera” “Several studies have shown a positive correlation between concentrations of inorganic N in surface water and larval abundance for malarial Anopheles sp mosquitoes, as well as for Culex sp and Aedes sp, carriers of La Crosse encephalitis, Japanese encephalitis, and West Nile virus.” “ Townsend et al. (2003) noted that the bacterium Vibrio cholerae is associated with a wide range of marine life, and that outbreaks of cholera have long been known to be associated with algal blooms in coastal waters under eutrophic conditions. A toxigenic V. cholerae 01 biotype El Tor has been isolated from macrophytes in both seawater and fresh water, and toxic and non-toxic strains have been isolated from brackish waters and estuaries, according to Borroto (1997). Marine plankton (phytoplankton and zooplankton) and detrital particles can serve as attachment vectors for V. cholereae. However, Vibrio cholerae growth can occur in oligotrophic freshwater, but mesotrophic conditions may be conducive to sporadic epidemic outbreaks (Vital et al., 2007). Jahid et al. (2006) showed that the toxigenic V. cholerae O1 N16961 has the ability to develop a large polyphosphate high-energy depository which enhances its capacity to survive environmental stresses in a low-phosphate environment.”
Among countries with WHO-reported malaria cases, those with high per-capita rates of malaria tend to have low rates of fertilizer use per unit of agricultural land. Statistical correlation does not infer cause and effect, but the data in Figure 3 do not support the hypothesis that nutrient availability associated with more intensive fertilizer use increases malaria incidence. Townsend et al, 2003 “concurrent increases in mosquitoes and eutrophic conditions are probably species, site, and season specific. In general, as with many ecological responses to changing N, the dynamics of a given disease vector are likely to be complex, driven not only by the organism’s direct response, but also by those of its food sources, and of the parasitic (Comiskey et al. 1999) and predatory species that affect its abundance.”
The fertilizer industry’s nutrient stewardship concept links management of plant nutrition to sustainability. The fertilizer rights—source, rate, time, and place—are connected to the goals of sustainable development. The connection between the practices and the benefits must be understood well, not only by crop producers and their advisers, but also by those who purchase the products of cropping systems and those who live in the environment impacted by those systems. Programs involving payments to farmers for ecological goods and services—for example, carbon offsets related to greenhouse gas mitigation, loading reductions for water quality credit trading, etc.—depend on a clear public understanding of these linkages and a common language and vocabulary relating to fertilizer management. The 4R nutrient stewardship concept defines the right source, rate, time, and place for fertilizer application as those producing the economic, social, and environmental outcomes desired by all stakeholders to the plant ecosystem. For stakeholders, the 4Rs support an accurate understanding of the big picture, even for those who may not understand all the details of managing crop nutrients.
Two important paths to solutions: Fertilize staples with micronutrients – works for Zn, Se, and I Ensure that non-staple crop production flourishes – what is the fertilizer industry’s role? An important part of the overall solution is to improve the productivity of a long list of non-staple food crops. Because of the large number of foods involved, achieving this goal requires a very large investment, the dimensions of which are not addressed here. Each chapter of this book will challenge the industry with new opportunities. How can our industry help prevent the substitution of non-staple crops by staples? Expanding both is in the best interests of the industry. The most common trace element deficiencies in order of prevalence are iron (~1.6 million; de Benoist 2008a), iodine (~2 billion; de Benoist 2008b), and zinc (~ 1.5 billion; Hotz 2004), most likely followed by selenium (Brown 2002) and copper (Madsen 2007). Recently published data indicate importance of nitrogen fertilizers in improving root uptake and grain deposition of Zn and Fe in wheat (Kutman et al. 2010). Generally, grains with high protein concentration contain also high amount of Zn and Fe, suggesting that grain protein is sink for Zn and Fe. Chapter 2: Micronutrient Malnutrition: Causes, Prevalence, Consequences, and Interventions. Howarth Bouis, Erick Boy-Gallego, J.V. Meenakshi
Even in regions of the world where zinc deficiency is relatively rare, syndromes have been detected. A study from my home province in Canada published the American Journal of Clinical Nutrition in 1989 found an association between low Zn levels, impaired taste acuity, and growth response to zinc supplements.
Welch and Graham. Chapter 3. Perspectives on Enhancing the Nutritional Quality of Food Crops with Trace Elements. “ Micronutrient malnutrition (which includes both trace element and vitamin deficiencies) is the result of dysfunctional food systems based in agricultural systems that do not meet all human nutritional needs.” “ This review concludes that it is imperative …that fertilizer technology be used to improve the nutritional quality of staple food crops that feed the world’s malnourished poor. ” “ The human population is already as much as three times the population defined by global ecologists as sustainable (Evans, 1998)” B – second most common deficiency for plants, not established as essential for humans Fe- rarely deficient for plants, most common deficiency in humans. Se and I – deficient for many humans but not for plants. Micronutrient deficiencies the direct result of the first green revolution; second GR must focus on avoiding them. “when soil-Zn status is low, additional N and P aggravated the low Zn status of the soil/crops and induced more extensive and overt deficiencies of Zn in these new varieties” “ We argue that fertilizer enhancement of the trace elements Zn, I, Fe, Co and Se and the deployment of provitamin A carotenoid-rich target crops together must rank of equal status with yield enhancement and environmental sustainability in this new effort for food security and healthier lives for all.” Table 7 – Se promotes bioavailability of I Cd, Hg, Pb as antinutrients affecting trace element bioavailability.
Zinc in Soils and Crop Nutrition B. J. Alloway Second edition, published by IZA and IFA Brussels, Belgium and Paris, France, 2008 “ Thus, the overall extent of Zn deficiency in world soils matches the extent of Zn deficiency in the human population and published maps for each factor are remarkably similar (Hotz and Brown, 2004; Alloway, 2008; Graham, 2008).” “ It is therefore not surprising that there is a close geographical overlap between the reported soil Zn deficiency and incidence of human Zn deficiency in different countries (Cakmak, 2008). ” “ plant breeding and agronomic biofortification approaches should not be considered as separate approaches to the problem; by contrast, they are complementary approaches and act synergistically ”
“ genetic biofortification may be more suitable for increasing pro-vitamin A carotenoids and Fe, whereas an agronomic strategy may be more effective for Zn, Se, and I “ “ In Xinjiang province in north-west China, potassium iodate (5%) was dripped into irrigation canals and resulted in a three-fold increase in soil I levels, a two-fold increase in wheat straw I, a 50% reduction in infant mortality, and IDD were largely eliminated. Benefits were evident up to seven years later (Cao et al 1994; Jiang et al 1997). This program provides an example of effective agronomic biofortification by fertigation. ” “ biofortification of plants with Co can benefit humans if provided through plants consumed by ruminants, which incorporate it in vitamin B12.” “ N and Zn fertilization have a synergistic effect on grain Zn concentration. ” – Kutman et al, 2010.
“ Se was found to be an essential constituent of the antioxidant enzyme glutathione peroxidase (GPX)” “ Several epidemiological studies have found Se status to be inversely associated with cancer risk, and Se-intervention has been found to reduce cancer risk in studies with a wide variety of animal tumor models. While relatively few clinical trials have been conducted to date, all but one have shown cancer risk reduction due to Se. The use of Se-enriched foods may be an effective and sustainable means of increasing Se intakes to support good general health and reduce cancer risk.” By 1990, the per-capita intake of Se in the Finnish diet was estimated to have more than quadrupled, increasing from 25 to 110-120 µg/day with 20% coming from cereals and 40% coming from meats and dairy products. Within four years, Se concentration in the serum of Finnish adults increased from an average of 70 ng/ml to one of nearly 119 ng/ml – one of the highest levels in Europe and approaching levels found in North America. Subsequent adjustments in fertilizer Se levels can be seen has having played through the Finnish food system, affecting crop Se levels and, ultimately, the Se status of the population