Fertilizer International 499 Nov-Dec 2020
30 November 2020
More bags of soybeans with POLY4!
AGRONOMY AND PRODUCTS
More bags of soybeans with POLY4!
The polyhalite product POLY4 offers a balanced and sustained supply of essential plant nutrients throughout the crop cycle – making it a highly-attractive, natural, multinutrient option for soybean fertilization. Lino Furia, Valter Asami, and Reinaldo Bello of Anglo American Crop Nutrients outline its many crop benefits.
Soybeans are widely grown for their high protein and oil content. They also provide an excellent source of dietary nutrients, including fibre, iron, manganese, phosphorus and folate. Because of this, soybeans have undoubtedly become one of the world’s most important crops, being widely consumed as a source of vegetable oil, animal feed, soy sauce and milk, tofu and textured vegetable protein.
Three countries – Brazil, Argentina and the United States – produce approximately 82 percent of the world’s soybeans at present, with Brazil leading the pack as the primary producer. Indeed, Brazil’s farmers are expected to deliver a record 133 million metric tonne soybean harvest in 2020/21, according to USDA’s latest forecast, up six percent from last season’s record. Soybean yield for this year’s crop is also forecast at 3.45 tonnes per hectare (t/ha) – the second highest on record – only slightly down on the record yield of 3.47 t/ha achieved in 2017/18. Furthermore, Brazil has now overtaken the US to become the world’s top soybean exporter, a position the country is projected to retain through to 2029.
- Brazil’s favourable climate which provides the ability to produce two crops from the same acreage in a single year
- The ability to use this same land for livestock pasture during dry seasons
- The emergence of new soybean varieties with a reduced growth cycle and higher nutrient demand
- The expansion of the area of land under cultivation in the Cerrado (Brazilian savannah).
Brazil has grown into one of the world’s largest fertilizer consumers, relying heavily on imported potash, phosphate and nitrogen fertilizers. This has been necessary to maintain the country’s status as a global agricultural powerhouse and sustain domestic crop productivity levels.
Typically, Brazil’s soybean farmers use muriate of potash (MOP) as their primary source of potassium, consuming more than 10 million tonnes of MOP a year. Traditionally, sources of phosphorous, sulphur and calcium are also provided by applying monoammonium phosphate (MAP), single superphosphate (SSP) and triple superphosphate (TSP). Soybean alone accounts for almost half (47 percent) of overall Brazilian fertilizer consumption (Figure 1). Around two-thirds of fertilizers in Brazil are applied as NPK blends, with the remainder applied as straight fertilizers.
Treatment transformation
Soybean production accounts for forty percent of Brazilian agricultural output. It is therefore unsurprising, given its prevalence, that Anglo American Crop Nutrients has made testing the effects of its polyhalite-based fertilizer – POLY4 – on soybean performance a priority in Brazil. Fifty-seven successful crop demonstration trials were completed in the 2019/20 season in collaboration with CIBRA, our Brazilian partner (Figure 2).
Soybean has a notably high phosphorous and potassium demand. Regionally, Brazilian soybean farmers typically apply these in equal amounts. Farmers in the south, for example, usually use 70 kg of P2 O5 and 70 kg of K2 O per hectare. In the north of Brazil, meanwhile, where soils are not as fertile, 90 kg of P2 O5 and 90 kg of K2 O per hectare are applied. Nitrogen, in contrast, is not applied in large amounts because soybean is a nitrogen-fixing legume.
Lime and gypsum are also commonly used by Brazil’s farmers for soybean fertilization. Lime, which offers magnesium and calcium carbonate, is an important soil amendment that helps adjust soil pH. However, its limited solubility means lime is generally unable to meet crop nutrient needs, especially at times when these are most required.
Gypsum supplies both calcium and sulphur. It also reduces the aluminium toxicity of highly-weathered Brazilian soils. Frequent gypsum application, as a standard practice, promotes potassium and magnesium availability. But it only achieves this at a medium rooting depth. POLY4 – in contrast – promotes these same nutrients throughout the entire rooting depth.
What is often most important to soybean farmers is nutrient availability. The increased nutrient demand of newer, higher-yielding soybean varieties means nutrient supply must be correspondingly improved. Trial results show that POLY4 successfully boosts agronomic performance by supplying potassium, sulphur, magnesium and calcium in one product. Importantly, it supports season-long crop nutrient demand while also increasing resilience to leaching.
Polyhalite granules are also effective at helping meet soybean’s high sulphur demand. Additionally, the combination of nutrients supplied by POLY4, including soluble magnesium and calcium, not only improves soybean yields, it also improves residual soil nutrient levels for the following rotation crop.
More bags of beans
In Brazil, the adoption of a POLY4 fertilizer plan has achieved positive results in 75 percent of soybean crop demonstration trials. During these trials, the composition of dry blends was varied to match regional nutrient requirements, with individual treatments being tailored in line with local recommendations.
EMBRAPA, the National Brazilian Agricultural Research Corporation, states that for a soybean yield of 4.2 t/ha, the following amounts of nutrients are exported by the crop:
- 85.3 kilograms of K2 O
- 14.1 kilograms of S
- 8.6 kilograms of Mg, and
- 12.2 kilograms of Ca.
For POLY4 fertilizer plans, dry blends were formulated by mixing POLY4 with MOP, to complement potassium supply, and with either MAP or TSP to provide a source of phosphorous.
The application of two hundred kilograms per hectare of POLY4, as a common baseline component, transforms the performance of fertilizer plans – by delivering 28 kilograms of K2 O, 38 kilograms of S, 7.2 kilograms of Mg and 24 kilograms of Ca per hectare
Brazil’s soybean farmers are generally receptive to new products and innovative technologies. That makes them very interested in any fertilizer source that offers prolonged nutrient availability and increased productivity.
This is especially true for the cultivation of new soybean varieties as these demand a timely nutrient supply due to their shorter production cycle. While traditional soybean varieties with a 130day growing cycle are still used in some regions, new plant breeds with a 90-day cycle are being grown more and more in the majority of Brazil’s soybean-growing areas. The adoption of soybean varieties with a shorter production cycle is advantageous as it allows the cultivation of succession crops – mainly corn, wheat and cotton – in the same year.
On average, POLY4 achieved a four percent yield advantage (Figure 3), with nine demonstration trials showing yield improvements in excess of ten percent. The progress of the recent crop demonstration trials was regularly observed by CIBRA and Anglo American agronomists. The team monitored and collected a range of biometric data, including the number of pods and beans per pod, and determined plant nutrient levels using leaf analysis. Visual differences, such as crop size and root length, were also recorded for POLY4 treatments versus standard practice (Figures 4 & 5).
Positive results confirm that POLY4, by providing a balanced mix of nutrients and a sustained nutrient supply, ensures the continued delivery of nutrients at the time when crops most need these.
Smooth operation
Within Brazil, soybean cultivation is mainly divided between eight states, with most farms ranging in size from 1,000 to 10,000 hectares. At the upper end of this size range, operational costs are a big focus for Brazil’s mega farmers. To efficiently cover the large land area on such farms – whether for fertilization, planting or harvest – good farm infrastructure is necessary. Farmers also need to start applying fertilizers at least thirty days before planting to ensure timely coverage. However, application this early exposes fertilizers to nutrient losses through leaching.
Moreover, soybean farmers in Brazil typically undertake three fertilizer runs each season. Phosphorous is applied firstly, then potassium, followed by the separate application of gypsum. While phosphorus and potassium sources are spread at 36 metres, gypsum, being in powdered form, is spread at 12 metres. This necessitates the use of different spreading equipment and additional resources. Each additional pass also results in another zone of soil compaction in the crop.
When it comes to simplifying on-farm operations, POLY4 provides an effective and much needed solution. Polyhalitebased granules, because they offer all the required nutrients in one product, can be supplied to crops in one application. This makes life easier for the farmers by dramatically reducing both the number of field runs and their labour costs. POLY4, due to its gradual and sustained dissolution, also fits in well with the farmer’s business cycle. An early application of the product meets coverage demand and then ensures nutrients continue to be available throughout the growing season whenever required by crops.
Better blends
Soybean farmers in south Brazil prefer to apply NPK blends in-furrow as starter fertilizers, traditionally using blends such as 0-18-18 or 0-20-20. This is far from ideal, however, as the high potassium concentration within the furrow suppresses root growth due to the osmotic effect of increased soil salt levels. Agronomists and cooperatives in south Brazil are currently running a major campaign to combat this. The campaign recommends the broadcast application of potassium and also promotes the replacement of traditional blends.
An NPK starter blend that partially replaces MOP with POLY4 and replaces SSP with TSP offers many benefits. POLY4based blends provide a comprehensive and better balanced mix of nutrients, with more sulphur and magnesium and – beneficially – less chloride.
The provision of two different sources of potassium within the blend (Figure 6) also guarantees its season-long availability for plant root absorption. These changes to standard blends, especially the inclusion of POLY4, matches nutrient release to the soybean growth cycle. They also confer positive advantages in terms of farm logistics and soil structure.
Supporting soil
When asked, Brazilian soybean farmers will often rank the weather as their highest challenge. Less than ten percent of agricultural land in Brazil is irrigated, the majority being rain-fed. This reliance on rainfall can be a disadvantage, given that Brazil is experiencing longer periods of dry weather and drought as a consequence of climate change and extreme weather conditions. These increasingly arid conditions have repercussions as they force plant roots to grow deeper in search of water and nutrients.
Aluminium toxicity and nutrient deficiency in Brazil’s acidic soils are two other issues of major concern to farmers. Indeed, the aluminium toxicity of soils is a primary constraint on crop biomass production in Brazil and the main factor limiting plant growth. Because of this, farmers need to regularly re-apply lime or gypsum to depress soil aluminium concentration. However, the neutralisation of aluminium by gypsum is only a temporary fix, especially within the deep soil profile (20-40 centimetres). Toxicity generally returns quickly after applications stop.
In 2018, a São Paulo State University (UNESP) study examined the soil benefits of POLY4 versus those of gypsum. The study compared sulphur and calcium delivery and observed potassium and magnesium distribution within the soil profile. Results showed that gypsum only improves calcium availability in the upper soil profile, while the calcium released by POLY4 was available at all depths. In doing so, POLY4 encouraged root growth, supported nutrient and water uptake, and helped to protect crops from drought stress. In addition, the higher solubility of the sulphate in POLY4, relative to gypsum, enhanced soil SO4 concentrations at both shallow horizons and deeper in soils.
Additionally, the 2018 study showed that POLY4 improves potassium availability to roots as deep as 60 centimetres. The product also enhances magnesium availability in the root zone at soil depths of 40 centimetres and below. It was concluded that POLY4 was able to add more magnesium to soils both at shallow depths and deep down. Gypsum, in contrast, promoted the leaching of magnesium. After nine months, it increased magnesium availability at a depth of 40 centimetres but depleted availability at shallow soil levels.
Overall, our 2020/21 trial results show that POLY4 offers a balanced and sustained supply of essential plant nutrients throughout the crop cycle – making it a highly-attractive, natural, multi-nutrient option for soybean fertilization.
A sustainable solution
Soybean cultivation in Brazil has improved in recent years, due to greater understanding of agronomic and climate factors, and the introduction of soil conservation management practices. Over the years, this has allowed degraded land to be converted for productive agricultural use. Likewise, no-tillage systems and more efficient fertilizer use have both contributed to greater productivity in the Cerrado region, and made management systems possible that allow two crops to be harvested annually.
Using POLY4 as part of a soybean fertilizer plan delivers a range of obvious benefits. These include yield improvements, more balanced crop nutrition, sustained nutrient delivery, and more efficient on-farm operations. But ensuring the sustainability of our agriculture and food systems is also an economic and environmental imperative.
In particular, every effort needs to be made to maintain the existing fertility of arable land and ensure that resources are used efficiently. Balanced nutrient supply undoubtedly plays a vital role here, being the key driver of fertilizer use efficiency. The use of POLY4, a natural resource with an inherent low carbon footprint, can clearly help. In Brazil and other countries globally, we believe POLY4 will contribute to the development of sustainable agricultural solutions that will be economically viable for farmers and their communities for generations to come.
About the authors
Lino Furia is the lead regional agronomist and Valter Asami a regional agronomist for Latin America at Anglo American Crop Nutrients. Reinaldo Bello is the company’s head of the Americas. For more details of the company’s under-construction, UK-based Woodsmith Mine project go to page 49.
