Good crop nutritional health supports several physiological and disease defense functions. Reduction in tissue potassium leads to:
Yield and quality penalties;
Inefficient nitrogen use;
Drought and/or cold susceptibility.
We assessed the effectiveness of POLY4 on tomato bacterial spot caused by Xanthomonas bacteria. This pathogen affects tomato yield and quality in many major tomato-producing countries.
In this second year trial, in partnership with University of Florida, fertilizer treatments were incorporated into the soil at the start of the trial. Plants were inoculated with a bacterial spot suspension at 53 and 67 days after planting. Disease severity and plant height were assessed 64 and 98 days after transplanting.
Various fertilizer sources were used to apply a range of K, S, Ca and/or Mg combinations.
• Supplying potassium significantly reduced
the severity of bacterial spot;
• POLY4 supplied potassium, sulphur, magnesium and calcium ensuring the highest reduction
The CRH of fertilizer is the value of relative humidity, above which a fertilizer will absorb moisture and below which it does not absorb moisture. Water absorption influences caking propensity which leads to difficulties in handling and spreading.
A typical curve from which CRH is determined compares uncoated POLY4 with coated MOP in the graph below. CRH values of 70% for MAP, DAP, MOP and urea, and lower values — near 55% — for blends have been reported.
Uncoated POLY4 has a CRH of 70%. This is similar to other substitute products such as MOP (72%), giving blenders and growers confidence in the product’s shelf life.
The compatibility of POLY4 is essential since many fertilizers are sold as blends. Incompatible products often result in caking, which is affected by humidity, particle shape and size, composition, storage duration, temperature and pressure.
Blending fertilizers require consideration of all components’ compatibilities to prevent caking and ensure safety. International Fertilizer Development Center (IFDC) is an established industry specialist. Using a wide range of likely fertilizer combinations, IFDC carried out advanced testing on POLY4 to determine blend compatability.
Testing took place over an extended period in order to mimic industrial conditions. Materials were combined and blended such that the total sample (100 grams), occupied two-thirds of a 200 mL glass bottle. The samples were then tightly capped and placed in a convection oven at a temperature of 30°C for 30 days. The mixtures/bulk blends were inspected daily for signs of incompatibility. The chemical analyses of tested materials were performed according to the Association of Official Analytical Chemists (AOAC) methods.
After testing, all mixtures remained free-flowing through the duration of the test. The results showed that POLY4 is a compatible input for blending into NPK fertilizers.
The potential storage life of fertilizer blends can be estimated during the accelerated caking test. Inclusion of POLY4 in steam-granulated NPK compounds reduced caking and improved caking resistance, which was tested using the small-bag technique. The results showed that using POLY4 in compounds gave a longer storage life, which is desirable for blenders and growers.
Resilience to handling is important during transit and for on-farm use of product. Minimising degradation improves spreading patterns supporting farm economics. Inclusion of POLY4 in steam-granulated urea and AN-NPK compounds reduced degadation from abrasion to near zero.
Fertilizers that generate dust make fertilizer-handling difficult and are undesirable by manufactures, blenders and customers. Dust presents an inhalation safety hazard and makes fertilizer handling difficult. The higher surface area of dust particles can lead to a greater attraction of moisture, consequently increasing caking propensity and lowering shelf life.
POLY4 positively reduced dust in steam-water granulated NPK compounds. For steam-water granulated urea-NPK an inclusion of ~50% POLY4 reduced dust by 82%. For steam-water granulated AN-NPK product, POLY4 lowered dustiness by 24%.