Zeolite for Agricultural Crops

Zeolite-enriched manure for agricultural fields

Natural zeolites have been used successfully since the 1960s for fertilizing agricultural crops. Utilizing zeolite’s cation exchange capability, they are first saturated with a concentrated ammonium ion solution and then incorporated into crop soils. Because surface-colonizing microbes can access nitrogen sequestered within zeolite, zeolites saturated with ammonia-N have proven to be an excellent long-term, slow-release fertilizer when applied to agricultural crops. The key difference here is that the ammonia zeolite sequesters comes only from the animal manures naturally – in other words, they have already been paid for though feed rather than having to pay more for synthetically manufactured ammonia.

In fact, incorporating zeolite into CAFO operations is a technologically simple approach for minimizing ammonia losses from CAFOs thereby improving animal health and occupational safety. Furthermore, unlike fresh manure, zeolite-enriched manure can be stored or composted with no loss of nitrogen. This allows farmers to apply the zeolite-enriched manure to agricultural fields at any time without creating environmental risks. Applying zeolite-enriched manures to agricultural fields has many advantages over applying ordinary (unprocessed) manure:

• The sequestering of ammonia by zeolite maintains a N:P ratio in the zeolite-enriched manure that is more balanced with respect to crop nutrient requirements. When applied to field crops, this more nutrient-balanced natural fertilizer reduces the risk of phosphorus saturation in soils and subsequent soluble phosphorus leaching into surface and groundwater.

• Because of ammonia sequestering, the zeolite-enriched manure can be applied at different times of year while still maintaining a high N content, but with minimal odors and a greatly reduced risk of nitrate leaching into surface and groundwater.

• Zeolites incorporated into soils can still take up and release ammonia produced from organic decomposition in the soils and from subsequent fertilizer additions –which promotes further on-farm recycling of nitrogen originally purchased as feed.

• The cation-exchange properties of zeolites also increase the capacity of fields to safely sequester trace heavy metals found in manures.

• The ability of zeolite to absorb water makes composted manure volumes smaller and easier to manage and transport; later it can release absorbed water into the soil during dry periods.

• Unlike ordinary fresh manure, the relatively dry compost does not coat crop leaves, which causes salt burns and reduces photosynthetic activity.

• The consistency of zeolite-enriched manure is more uniform, reducing the risk of over or inconsistent application.

• Zeolite-enriched manure increases soil filtration rates, which in turn increases nutrient availability to crops, stabilizes soil moisture, and reduces surface erosion and associated losses of nitrogen and phosphorus.

• Since zeolites do not break down under ambient conditions, field crops will continue to benefit long after the composted manure is applied and totally decomposed. Zeolite accumulation in agricultural soils will benefit both water retention/management and crop yield consistency and sustainability.

Zeolite-enriched manure versus synthetic fertilizers

Farmers who do not utilize on-farm produced livestock manure for crop production must purchase synthetic fertilizers. Although there is a long tradition of using livestock manure for fertilizing field crops, the uncertainty of the manure’s nutrient content (due to nutrient losses during storage from leaching, runoff, and volatilization) and its variable consistency have made synthetic fertilizers an attractive, albeit expensive, alternative. However, manure composted with natural zeolites provides an even better alternative. Table 1 below summarizes the relative benefits to livestock manure management and field crop applications of applying zeolite-enriched manure versus ordinary (i.e., no processing) manure, composting manures without natural zeolites, and the use of synthetic nitrogen-phosphorus-potassium (N-P-K) fertilizers.

Table 1. Relative agricultural benefits of livestock manure enriched with natural zeolites compared with ordinary (fresh or aged) manure or synthetic N-P-K fertilizer.

Adapted from Krason and Knud-Hansen (2004)

This demonstrates that composting animal manures with natural zeolites can resolve both the environmental and economic concerns of CAFOs, and a major liability of manure disposal can be converted into a valuable natural organic fertilizer with a balanced N:P ratio and minimal N losses from the farm to the environment. Zeolites allow a greater percentage of the original feed nutrients to be incorporated into beneficial products. Recycling these nutrients within the farm promotes both agricultural and economic sustainability, a central concept behind integrated farming systems. Zeolite-enriched manure can also become a valuable marketable commodity for the farmer.

Zeolite for water efficiency

Natural zeolites can absorb up to 70% of their weight in water when completely dry or dehydrated. Water is contained within the lattice, honeycomb crystalline structure. And, unlike bentonite clay, zeolite does not compress, expand or change shape when hydrated and dehydrated. This unique capacity for dehydration-rehydration – that is, to absorb water when available and release this water during dry times – can provide a huge benefit for all agricultural systems.

For manure management, zeolite significantly accelerates the drying time making manure storage and transport easier. This is also important in animal stalls as well. With zeolites taking up excess water in the manure, together with ammonia sequestration, the animals are less prone to hoof infections or mastitis in dairy cows. A drier, less odorous environment is much healthier for the animals, as well as for CAFO operators.

Zeolite-enriched agricultural soils provide a valuable benefit during times of both rainfall and drought. Acting as a crystalline sponge, zeolite will absorb water during heavy rainfalls, reducing agricultural runoff from the fields. This helps keep nutrients on-farm, while reducing erosion impacts following storm events. During dry periods zeolite will dehydrate, releasing water previously stored within its lattice structure.

This unique property of zeolite is especially important for agricultural systems in semi-arid conditions of the western US. Water is an extremely valuable commodity and can be a huge on-farm expense. The more zeolite-enriched manures are applied to agricultural fields, the better these fields will be able to minimize deleterious impacts on both crops and soils during storm and drought conditions. Water demands for irrigation should be more consistent and also quantitatively reduced throughout the growing season – in other words, better and more consistent crops produced with lower farmer expenses for purchased water and inorganic fertilizers.