[hepr-vn] More N-fertilization is not the way to go for rice

[Vern Weitzel]

Subject: [SEA-SPAN] More N-fertilization is not the way to go for rice
Date: Thu, 14 Feb 2008 21:49:00 +0700
From: user at sea-user.org


More N-fertilization is not the way to go

By Zac B. Sarian
Source: Manila Bulletin, 14 Feb 08

During the celebration of the Bulletin�s anniversary last February 2, we had 
occasion to talk to Dr. William Padolina, former Science and Technology 
Secretary, and now deputy director general for partnerships of the International 
Rice Research Institute (IRRI) based in Los Baños.

He was inviting us to Los Baños so we could be updated on the latest 
research developments in rice which he said are very exciting. Any example of 
such research development?

He mentioned the improvment of the photosynthetic pathway of rice which is C3. 
Corn is much more efficient in utilizing the radiation from the sun to produce 
biomass and grains because it has a photosynthetic pathway of C4. The upgrade in 
the photosynthetic pathway of rice to C4 could mean more than 10 percent 
increase in yield. And that�s one of the strategies IRRI researchers have been 
pursuing.

The upgrade of the photosynthetic pathway is one of the new strategies to 
inrease rice yields. The old strategy of using more and more nitrogen 
fertilizers to hike yields will only damage the environment. Dr. John Sheely, 
IRRI crop ecologist and modeler, explains it best in an IRRI publication that 
came out way back in 2001, titled "Rice Research: the Way Forward." In the past, 
he said, higher yields have depended on increased use of organic and inorganic 
fertilizers to supply nitrogen to the plants. This no lopnger represents the way 
forward because the use of organic fertilizer often stimulates the emission of 
methane, and inorganic nitrogen fertilizers can stimulate the emission of 
nitrous oxide. Along with carbon dioxide, these are the two most damaging 
greenhouse gases and any proposal to boost rice production simply by increasing 
fertilizer use would risk making the world�s climate even worse.

The IRRI publication continues: "Converting a plant from C3 to C4 would involve 
a rearrangement of cellular structures within the leaves and more efficient 
expression of various enzymes related to the photosynthetic process."

"All the components for C4 photosynthesis already exist in the rice plant," Dr. 
Sheely says, "but they are just distributed differently and are not as active."

Dr. Sheely adds that "plants with C4 photosynthetic pathway are better equipped 
to cope with the climate changes that are expected as a consequence of global 
warming. They operate well at high temperature, they�re extremely 
water-efficient, and they require less nitrogen."