Fertilizer International 510 Sept-Oct 2022
30 September 2022
Fuelling balanced crop nutrition with POLY4
The fertilizer price and supply chain shocks caused by the war in Ukraine have supercharged the debate about the shift to more sustainable and efficient crop nutrition – with farmers and governments urgently looking for different approaches to maximise crop productivity.
The almost threefold rise in average fertilizer prices since mid-2021 was singled out by Qu Dongyu, director-general of the UN Food and Agriculture Organization, at a meeting of the G20 in July. He highlighted the risks to global food production from fertilizer supply shortfalls in the upcoming planting season. Qu made it clear that now, more than ever, farmers need to produce more from less by making better and more efficient use of fertilizers.
Throughout the agricultural industry, such high-level concerns have brought about a renewed focus on maximising nutrient use efficiency – whether through the adoption of alternative practices, technologies or products.
Back to basics to move ahead
“If we want to take efficient and sustainable crop nutrition seriously, we really need to go back to first principles,” says Ross Mitchell, head of agronomy at Anglo American’s Crop Nutrients business. “Liebig’s law says the availability of the most abundant nutrient in the soil is only as good as the availability of the least abundant nutrient in the soil.”
“Nitrogen, phosphorus and potassium will always be the powerhouses. But if you neglect the other nutrients, such as magnesium and calcium, not only can you inhibit your yield, you can also create long-term problems for the health and productivity of your soil.”
While Mg and Ca are not required in as large amounts as N, P and K – or even sulphur – for most plants, they still need to be available in sufficient quantities to improve and strengthen crop health and support crop quality. Magnesium is crucial for chlorophyll production and therefore photosynthesis, whereas calcium is the building block of all plant cell structures.
Anglo American’s polyhalite based product POLY4 product will be a significant new source of both these nutrients, with upwards of 10 million tonnes of polyhalite expected to be extracted annually from the company’s under-development Woodsmith mine in the north of England.
“POLY4’s sustained nutrient release profile will enable farmers to fill in those nutrient dips where supply doesn’t traditionally meet plant demand,” says Ross. “Those incremental improvements lead to big improvements in the ability of the plant to uptake other nutrients, such as nitrogen and phosphorous, just as Liebig’s law dictates. Overall, you are getting healthier, higher quality and greater yield of crops through improved nutrient use efficiency.”
Anglo American is investing heavily in creating a solid bank of evidence on the agronomic performance of POLY4 and its crop and soil benefits. With over 2,000 trials under its belt, including more than 1,150 commercial on-farm demonstrations, the company now has a robust vision for this polyhalite product and the opportunities its offers.
The value of magnesium and calcium
Magnesium plays a crucial role in crop development throughout all stages of the growth cycle. As an essential building block of chlorophyll, it is required by all crops to help generate energy from sunlight during photosynthesis. A consistent supply of magnesium also helps plants take up and use other nutrients. Plants deficient in magnesium, in contrast, produce less chlorophyll and are less able to transport carbohydrates.
Ensuring magnesium is readily available can therefore improve crop quality and make fertilizer applications more efficient. This is particularly important for high-value crops such as potatoes or tomatoes, for example, where having healthy looking and marketable produce is vital if growers are to achieve a good price for these ‘cash crops’.
Potato is known to be a magnesium hungry crop that can benefit from the application of POLY4. In recent German trials, POLY4 treatments outperformed standard fertilization practice for potatoes (K+S+Mg) by delivering yield gains of up to five percent (Figure 1). By providing nutrients in low chloride form, POLY4, as well as increasing yield, improved potato starch content by two percent. These potato trials were carried out across six German regions on different soil types, ranging from loamy sand to a silty clay with low potassium content.
POLY4 has also demonstrated yield and sugar content improvements with sugar beet. Trials in Poland assessed crop nutrition plans that incorporated POLY4 versus standard fertilizer practice for sugar beet with MOP (muriate of potash, KCl) and kieserite (MgSO4·H 2 O). The trials were carried out on two sites, one a silty loam and the other a loamy sand soil. POLY4 treatments performed well, delivering an average nine percent yield advantage for sugar beet at harvest (Figure 2). The sugar content of these harvested roots also improved by two percent.
Both these examples show the direct link between more balanced nutrient supply and both crop yield and crop quality improvements. The end result being a higher market value for harvested produce and therefore larger incomes for the farmer.
Calcium is another nutrient that plays an important role in balanced crop nutrition. In the tropical soils of Brazil, for instance, calcium is often used to strengthen and improve soil structure and to displace aluminium. Importantly, calcium also helps plants to resist disease, regulate water retention and strengthen their cell structure. These benefits in turn improve the post-harvest shelf life and storage ability of crops, factors which are vital in fresh produce markets.
POLY4 is granular with sustained release properties. This makes calcium available to the plant for a prolonged period, compared to conventional calcium sources such as lime or gypsum, which bind more easily to soil particles or leach through the soil profile. Furthermore, the calcium in POLY4 helps to increase the tensile strength of soil and its resistance to compaction. Improving tensile strength, by preventing soil movement and erosion, helps to minimise nutrient losses, while greater resistance to compaction, by maintaining a porous soil structure, helps improve drainage and prevent runoff.
What’s more, trials have shown how POLY4’s calcium content can help a plant’s disease resistance. A recent tomato trial in Italy, for example, demonstrated POLY4’s effectiveness at preventing calcium-deficiency disorders. The incidence of blossom end rot in tomato was markedly reduced in treatments with POLY4 versus treatments with SOP (sulphate of potash, K2 SO4 ) and kieserite (Figure 3).
In future trials, Anglo American’s agronomic team is planning to investigate POLY4’s effectiveness against other calcium deficiency disorders, such as bitter pit in apples or pod rot in peanuts. The calcium needs of peanuts are especially high, as the fruit develops by absorbing nutrients directly from the soil instead of transport via the roots.
Maximising nutrient use efficiency
POLY4 is a natural product offering a well-balanced supply of nutrients. These are completely plant available and not in competition with each other, as can happen with other compounds. POLY4 also spreads more evenly during application, making it easier for farmers to achieve a uniform nutrient distribution across the field.
“POLY4 is like an insurance product for farmers in tropical conditions,” says Lino Furia, Anglo American’s regional agronomy manager for Latin America.
“More balanced nutrients and uptake means better quality, healthier plants able to thrive in a wide variety of agroecological conditions and extreme weather situations,” explains Lino. “This is especially important for perennial crops like citrus or coffee, which require careful management and protection to produce a consistent high-quality crop – you cannot rectify mistakes later.”
Coffee, for example, requires good magnesium availability during blossoming, its point of peak demand, to ensure the fruit ripens consistently. Lack of magnesium can also lead to leaf sunburn and reduced fruit formation and uniformity. Yet local farmers, because they typically focus on N, P and K applications, often disregard secondary nutrients.
“Having a good process is crucial for coffee growers to achieve the consistency that buyers demand,” says Lino. “If you can supply a good balance of nutrients that are always available to the crop, particularly at peak demand, you will have a healthier plant that produces better fruit.”
He continues: “This is a far more sustainable approach, both environmentally and economically, than using a specialist product, like a foliar spray, to rectify a problem caused earlier in the growing process.”
“It’s like running a car – if you only use low octane fuel and do not service it frequently, eventually you will hit trouble. By supplying balanced crop nutrition, including magnesium and calcium, POLY4 will provide a solution for farmers to maximise the health and productivity of their crops consistently, whenever and wherever they need it.”
Challenging preconceptions
The concept that more balanced fertilizer practice leads to improved yields is not new. In the past, though, a farmer’s ability to achieve this was mainly dependent on product affordability and availability. Secondary nutrient and micronutrient products were not widely available and were usually only used by large-scale farmers on high value crops. Anglo American is seeking to turn these assumptions on their head.
“We’re challenging preconceptions of traditional fertilizer industry thinking, indeed of what a fertilizer really is,” says Dr Alexander Schmitt, Chief Marketing Officer of Anglo American’s Crop Nutrients business.”
“The current market for secondary nutrients is not a reflection of need, it is merely a reflection of the industry’s production capacity and old 20th century commoditised structures. But every plant needs just enough of these nutrients to maximise its health and vitality, and therefore the efficiency of the farm.”
“POLY4 is a way of ensuring that you are maximizing your crops’ chances of success and with the tonnages we plan to produce, we will be able to provide that security to many more farmers than the present market caters for.”
“We know that there is an expanding market for low chloride potassium and sulphur, and favourable trends for more sustainable, low emission products that protect and enhance the soil. Add to that the fact that it is easy to spread and blend, is suitable for organic farming and has a sustained nutrient release profile, and you have a product perfectly positioned to help solve the challenge of achieving more efficient and sustainable fertiliser practices on a large scale.”
“We are aiming to reimagine crop nutrition for the 21st century.”
