Plants as Source of Fertilizer and Forage
When the Mindanao Baptist Rural Life Center (MBRLC) Foundation, Inc. started its operation in the early 1970s in Kinuskusan, Bansalan, Davao del Sur, farmers from the nearby areas came and complained of low and declining farm income as their foremost problem.
One farmer reported that his corn production had dropped from 3.5 tons per hectare to about 0.5 ton per hectare. Other farmers said that yields of other crops had also-dropped 60-80% in the same period.
“Some farmers started planting permanent crops like banana, coffee, coconut, and fruit trees to augment their income,” recalled Harold R. Watson, the former MBRLC director. “But still, yields of the permanent crops were also very low.”
Trying to figure out what was really the cause of low yields, Watson and his colleagues at the MBRLC found out the main culprit: depletion of soil and nutrients through soil erosion.
“Soil erosion is an enemy to any nation – far worse than any outside enemy coming into a country and conquering it because it is an enemy you can see vividly,” said Watson in 1985, when he received the Ramon Magsaysay Award for peace and international understanding. “It’s a slow creeping enemy that soon possesses the land.”
Watson was bestowed the Nobel Prize of Asia for encouraging international utilization of Sloping Agricultural Land Technology (SALT) and other sustainable farming systems which MBRLC has developed through the years.
“Basically, SALT is a method of growing crops, both annual and permanent crops, between contoured rows of nitrogen-fixing species set up four to six meters apart,” explains Roy C. Alimoane, the current director of MBRLC.
The nitrogen-fixing species are planted densely in double rows to make hedgerows that serve as erosion barriers. When the shrubs are 1.5 to 2 meters tall, they are cut back to about 40 centimeters and the tops are piled in the 3-5 meter alleys where crops are growing. “The leaves of the shrubs make very good nitrogen-rich fertilizer and also add organic matter of the soil,” Alimoane points out.
A study conducted at the MBRLC showed that a farm tilled in the traditional manner erodes at the rate of 1,163.4 metric tons per hectare per year. A SALT farm erodes at the rate of only 20.2 metric tons per hectare per year.
The rate of soil loss in a SALT farm is 3.4 metric tons per hectare per year, which is within the tolerable range. Most soil scientists place acceptable soil loss limits for tropical countries like the Philippines within the range of 10-12 metric tons per hectare per year. The non-SALT farm, on the other hand, has an annual soil loss of 194.3 metric tons per hectare.
In the beginning of the SALT system, MBRLC used ipil-ipil (known in the science world as Leucaena leucocephala). According to Watson, “ipil-ipil” helps to enrich soil and aid neighboring plants because of its foliage rivals manure in nitrogen content. Studies done in Hawaii showed that if the foliage is harvested and placed around nearby crops, they can respond with yield increases approaching those applied with commercial fertilizer.
There were more reasons: ipil-ipil’s aggressive root system breaks up impervious subsoil layers, improving moisture penetration . and decreasing surface runoff. Nutrients from deep strata are gradually deposited, on the surface through decay of the leaves and other plant parts; soil organisms increase, topsoil humus builds.
Then something went awry. The ipil-ipil was attacked by a psyllid (Heterophsylla cubana). In a workshop held in Bogor, Indonesia in 1989, the experts chorused: “The psyllid has been a threat to both industrial and small-farm use of leucaena for some areas. This pest has seriously reduced the value of the species for fodder, shade, and other uses.”
It was bad news for most farmers. But the good news was: MBRLC was already testing several other hedgerow species for its SALT system. “Even before our ipil-ipil was attacked by psyllid, we had already several options what to use, said Watson.
The MBRLC tested almost 50 species, mostly legumes. “The word legume basically means `pod bearing plant’ and the most common examples are beans and pulses,” said Jeff Palmer, who was head of the testing and development department of the center. Many plants in the legume family, however, are nitrogen fixing (NF) but there are also many which are not.
“Since verifying the nitrogen fixing ability of a plant involves a difficult technical process, we have always used the rule of thumb that a plant which produces good NF nodules on the roots must be nitrogen fixing,” Palmer said. “To qualify as having `good NF nodules,’ the plant must have many nodules which are moist and pinkish in color when crushed.”
As hedgerows for its SALT system, the following criteria were also added: coppices readily under heavy pruning (12 times per year), produces at least 25 metric tons of fresh biomass per hectare per year based upon 5-meter double hedgerow intervals, readily sets seed for farmer reproducibility, reproduces vegetatively, tolerates insects and pests, grows well when planted closely, adapts to a wide variety of soils and climates, grows ipto a tree (if left unattended), usable for forage, deep rooted, and with several uses (fencing, fuel, feed, etc.).
The top four species that MBRLC considered “very good” are Desmodium rensonii, Fleminqia mucrophylla, Indigofera anil, and Gliricidia sepium. “We recommend that farmers plant these four species in their farm. If one species is attacked by pests, there are three other species left,” said Alimoane.
Fleminqia macrophylla may be the most widely adaptable NF contour hedgerow species for Asia since it also originates in this part of the world. “Flemingia is the best hedgerow species in terms of providing a long lasting ground cover after trimming,” Palmer said. It is also a good forage for dairy goats.
Desmodium rensonii is “fairly unknown around the world” but is “possibly the best animal feed in the tropics,” Palmer said. With a crude protein content (23%) rivaling alfalfa in the temperate climates, rensonii has been successfully tested at the center as an animal feed for goats, sheep, cattle, rabbits, swine, and fish.
Indigofera anil shows promise in hedgerow systems, as an animal feed and as a fuel wood crop. In simple tests at the MBRLC, Nubian goats fed with a diet of 100% indigofera for over a year have grown well and even kidded.
Gliricidia sepium, locally known as kakawate, is one of the best hedgerow species around. This can also be given to goats, provided, it is combined with other forage crops like Desmodium rensonii and/or Flemingia macrophylla. Most people plant this species using cuttings but it can also be planted using seeds. “Directseeded planting have better tap root formation and less lateral root invasion into the alleyways of the SALT system,” Palmer said.
Unfortunately, kakawate seems only to set seed well in areas with dry zones having at least 4-6 month dry period. This is the reason why seeds for sale on this species are not available at the MBRLC.
Desmodium rensonii and Indigofera and are sold at the MBRC at Php350 per kilo. Flemingia macrophylla, hawever, can be obtained at a lesser price: PhP300 per kilo. “We can only provide seeds to our buyers when these are available,” Alimoane said. “So, they need to contact us first.”