Sustainable landscape management encourages the systems created by nature: healthy soils supporting healthy plants. The foundation of an organic program requires the plants and soils to be viewed as extensions of one another, existing in a perfect symbiotic relationship. This holistic, "bottom up" focus contrasts with the conventional maintenance mindset of treating specific plant health conditions from the "top down" through the application of synthetic chemicals.
Bridging from Conventional to Organic Methods
The early phase of our transition efforts focused on reducing or eliminating the use of all inorganic fertilizers, chemical pesticides, fungicides, and herbicides, and significantly reducing the use of organic nitrogen fertilizers in our maintenance programs. Our experience convinced us that chemicals and synthetics can be systematically eliminated and replaced by programmed encouragement of the natural cycles of support. Understanding as much as possible about the environmental conditions within our landscape, including public use patterns as well as aesthetic expectations was vital to creating a successful maintenance program. As you'll see, our programs are continuously adjusted to meet the needs of the various landscape systems.
Our Organic Landscaping Program consists of seven primary components:
Organic Soils Management
Restoring and maintaining the natural nutrient cycling system is the heart of any organic landscape program. The benefits of this approach include improved nutrient and moisture availability and retention, disease suppression, aeration, and degradation of harmful pollutants achieved through non-chemical or synthetic methods.
Nutrient Retention: beneficial organisms keep valuable nutrients in the proper root zone. Bacteria and fungi also prevent leaching; a process that removes nitrogen and other nutrients from the soil. Preventing this material from contaminating the water table is another important benefit.
Nutrient Availability: the symbiotic relationship between fungi and roots helps plants filter needed micronutrients from the soil. Protozoa feed on bacteria and fungi, excreting nitrogen in a form easily absorbed by plants. An organic program focuses on building up the components needed to optimize nitrogen and nutrient cycling.
Moisture Retention: organic matter retains water in the root zone long enough to be taken up by plants, dramatically reducing overall water use. Irrigation needs were reduced by 33% on our organic test plots in 2008.
Pest and Disease Control: beneficial nematodes and fungi protect the roots of plants from potentially harmful organisms always present in the soil.
Aeration: organisms aerate and give structure to the soil by creating air holes and drain pockets. This process reduces compaction and maximizes water availability to the root zone.
Degradation of Pollutants: properly managed soil includes organisms that consume a wide-range of pollutants across a variety of environmental conditions.
Comprehensive soil testing forms the basis of any successful organic maintenance program. The following three tests are required to fully understand soil conditions:
Biological Analysis: testing for fungi and bacteria as well as beneficial predators (protozoa and nematodes) takes much of the guesswork out of selecting the proper compost/organic matter amendment strategy. The nutrient cycling systems of different plants may require specific fungal or bacterial dominated soils to function optimally. Biological testing is not a replacement of standard nutrient, chemical, and textural analyses. It is simply an additional tool that can help provide a fuller picture of what's going on in our soil.
Some of the specific biological measurements include:
- Mycorrrhizal fungi form narrow threads in compost and attach themselves to root structures. These microbial organisms consume exudates from plant roots. The nutrients become stored as food and moisture for plants - to draw on when needed - as well as nematode predators. The waste from the nematodes also becomes food for the plants - completing this natural nutrient cycle.
- Bacteria also play a key role in plant nutrition by immobilizing nutrients in the rhizoshepere. These microbes decompose organic matter and ingest root exudates, preventing them from leaching out of the soil. These valuable nutrients are tied up in the bacteria until they are eventually released in the ammonium (NH4+) waste of protozoa predators, for use by the plant.
Chemical Analysis: required to determine the following:
- pH Levels
- Cation Exchange Capacity (used to measure fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination)
- Individual Nutrients (most commonly: Nitrogen, Phosphorus, and Potassium)
- Soluble Salts
Textural Analysis: determines the percentage of sand, silt and clay in a given soil. The ratio of sand, silt, and clay in soil determines its ability to hold moisture and nutrients.
Compost is the aerobically decomposed remnants of plants and food created through the management of heat, moisture, and aeration. The result is a nutrient-rich environment for beneficial bacteria, fungi, and protozoa that can be applied directly to the soils. These microorganisms control pests (pathogenic organisms) and aerate the soil, providing the opportunity for extended root development. At Harvard, all herbaceous and woody materials - along with a growing portion of food waste from dining halls and cafeterias - are collected for composting. When composting, emphasis should focus on the creation of a high quality end product and not just a way to get rid unwanted waste. These are precious resources that when handled properly will yield extremely valuable results. At Harvard, we are creating the following three basic types of composts, each used to address particular needs within our landscape systems:
Bacterial Mix compost are more dominant in bacterial feedstocks (hay weeds, coffee grounds, herbaceous material). Common plants that prefer bacterial soils (grasses, annuals, perennials, and vegetables)
Fungal Mix compost are dominant in fungal feedstocks (dry leaves, sawdust, wood chips, shredded newspaper). Common plants that prefer fungal soils (trees and shrubs)
Vermicompost is the product of some species of earthworms as they breakdown organic matter. Most of our vermicompost is used as a solid in planters, but is also an ingredient in many of our compost tea recipes. This compost is typically the highest in available nutrients.
Composting must be done carefully and systematically. Here are the keys to successful composting.
Temperature: for best results, temperatures within the entire compost pile must stay between 130-160 degrees F for approximately two weeks. Maintaining this temperature range is critical; warm enough to kill off weed seeds and pathogens yet still allowing for cultivation of beneficial organisms.
Aeration: during the two weeks when temperatures of at least 130 degrees F are required, turn the pile 2-3 times per week to allow air to infiltrate. This step is essential for maintaining proper temperatures and encouraging the development of beneficial soil organisms to breakdown organic material.
Moisture: too much or too little moisture will negatively impact the quality of the compost. A moisture rate of 35% to 45% is optimum. To determine this, grab a handful of compost from the center of the pile and squeeze it. The material should be moist to the touch but not drip. Too dry: add water and mix thoroughly. Too wet: turn more frequently and cover to protect from rain. The following are two basic compost recipes:
For Grasses, Annual, Perennials, and Vegetables Bacterial Mix - Feedstock Ingredients
- 45% Bacterial: hay, weeds, coffee grounds, herbaceous material
- 30% Fungal: dry leaves, sawdust, wood chips, shredded newspaper
- 25% Nitrogen: grass clippings, vegetable waste, legumes, manure
For Trees and Shrubs Fungal Mix - Feedstock Ingredients
- 45% Fungal: dry leaves, sawdust, wood chips, shredded newspaper
- 30% Bacterial: hay, weeds, coffee grounds, herbaceous material
- 25% Nitrogen: grass clippings, vegetable waste, legumes, manure
Important: To select the proper compost, identify the types of plants within your landscape. In general, turf, grasses, and perennials require higher bacterial populations, while more complex landscapes with trees and shrubs benefit from higher fungal populations.
Compost Teas are a specific liquid biological amendment made by coaxing the beneficial organisms from the compost and depositing them into an aerated water solution with various food sources. The advantage of the tea is that recipes can be developed and fine-tuned to target specific conditions and plant needs. Careful application of compost teas can speed up the process of balancing the soil biology... but achieving the proper mix requires time and testing. Remember, that the better the compost, the more effective the tea!
The following are some additional considerations for Compost Tea:
- During the brewing process bacterial populations, on average, double every half hour.
- Applications are particularly favorable for trees and lawns which require the beneficial organisms but not necessarily a high percentage of organic matter.
Pest and Disease Control
Our program uses only non-toxic methods for treating and preventing pests and disease by relying on the following processes and techniques:
- Aerating to reduce plant stress
- Monitoring moisture because inadequate moisture levels can weaken plants and make them susceptible to pest problems.
- Applying compost teas to suppress powdery mildew.
- Introducing and cultivating beneficial insects which prey on destructive insects.
- Manually removing infected tree and shrub branches.
- Manually removing weeds.
Properly managing water consumption is a vital component of sustainable landscape management. The goal of any irrigation program should be to apply the right amount of water in the right locations and at just the right time. Besides being wasteful and expensive, over-watering causes leaching of valuable soil nutrients and can damage plant health. Organic landscaping greatly increases moisture retention by encouraging deeper root growth so that conventional irrigation schedules can be significantly reduced or eliminated entirely. However, during periods of drought and transplanting operations additional water may be required.
Water is most efficiently applied through in-ground irrigation systems. While these systems typically have automated control features, it's important to closely monitor their use to ensure adequate coverage. We have also found that frequent adjustment to the automation schedules in response to changing environmental conditions is still required.
Proper Planting & Pruning Techniques
Proper pruning and installation of any landscape is essential. The following are a few techniques for ensuring the landscape gets a good start.
- A comprehensive soil analysis is needed to determine the baseline biological requirements.
- Plants should always be transported and handled carefully to avoid damage.
- Plants should be installed following the American National Standard for transplanting of trees, also known as ANSI A300.
- Careful pruning of inner and outer foliage encourages a natural growth pattern, increases photosynthesis, enhances the health of the plant, and reduces wind resistance.
Plant Selection and Placement
Location, location, location! It applies to plant placement as well. Choosing the proper plants and placing them in optimum areas is vital to building a sustainable landscape. Plants need good soils and adequate natural sunlight to flourish. They also need a spot where their natural size and shape will be uninhibited. Considerations of plant size, color, and suitability to the surroundings should include anticipated interaction with people as well as existing and future plants. Always think ahead before planting!