Table of Contents
Nutrient Management
A healthy crop requires a perfect match of nutrient supply with plant demand: enough to support high yield, the right mix to avoid deficiencies, and availability at the right time to achieve optimal growth.
NPK is Not Enough
Plants acquire most nutrients, dissolved in water, through their root system from soil and other indigenous sources such as decomposing crop residues. However, the indigenous nutrient supply, particularly nitrogen (N), phosphorus (P) and potassium (K), is typically insufficient to achieve high and profitable yield in cereal crops such as rice and maize. Additional nutrients, supplied by fertilizers, will need to be added to safeguard yields and food supply. However, with surging prices of farm inputs, especially fertilizer, farmers and policy makers may be tempted to cut costs by reducing the use of one or more fertilizer nutrients – a risky strategy. At some point, less fertilizer use can mean lower crop yield, less profit for farmers, and – eventually higher risk of food shortage in the country.
According to Dr Christian Witt, Director for Southeast Asia Program of the International Plant Nutrition Institute (IPNI), high fertilizer prices are the result of a tightening global market that follows the basic principles of supply and demand. The demand for food – and thus, fertilizers – has been increasing through the years, driven by population growth and increasingly diversified diets as income in developing countries grow.
Fertilizer production of some nutrients, on the other hand, has not always kept pace with demand and it will take some time and investment in production facilities to correct this. While the situation has eased a little in 2009, fertilizer prices may continue to remain relatively high in the near future. Farmers – especially those with low cash flows – will need to change their fertilizer strategies and make better use of fertilizers to optimize their production systems. Fortunately, new technologies are now available to assist farmers in their decision making.
As part of the comprehensive program of the Philippine government to raise food sufficiency level and ensure adequate, accessible, affordable and nutritious food for Filipinos dubbed as FIELDS (Fertilizer, Irrigation, Extension, Loans, Dryers and other post harvest facilities, Seeds and other genetic materials), the Bureau of Agricultural Research (DA-BAR) in partnership with the Bureau of Soil and Water Management (BSWM), the University of the Philippines Los Baños (UPLB) and the International Plant Nutrition Institute (IPNI), launched a national initiative to increase the productivity and profitability of maize (corn) farming through site-specific, integrated crop and nutrient management.
Site-Specific Nutrient Management
The project on Site-Specific Nutrient Management (SSNM) for Maize in the Philippines is part of a multi-national research initiative that aims to i) quantify and understand the yield potential of maize in favorable environments of Southeast Asia and ii) develop and evaluate a new SSNM appro ach and best crop management practices for maize through on-farm research in major agro-ecological zones of the Philippines, Vietnam, and Indonesia. Concepts of SSNM were first developed for irrigated rice in Asia, but its principles are generic and applicable to other cereal crops like maize. The SSNM approach strives to enable farmers to adjust fertilizer use to fill the deficit between the nutrient needs of a high-yielding crop and the nutrient supply from naturally-occurring indigenous sources, including soil, crop residues, manures, and irrigation water. SSNM does not specifically aim to either reduce or increase fertilizer use. Instead, it aims to apply supplemental nutrients from fertilizer at optimal amounts and times to match the needs of the crop.
SSNM provides guidelines and tools for site-specific management of N, P, K – the major nutrients needed by the crop, as well as other essential elements. One of the tools available for managing N is the leaf color chart (LCC). The LCC is a plastic ruler-shaped strip containing four or more panels ranging in color from yellowish green to dark green. It is used to assess the crop’s need for N based on the color of the leaves. Plants with dark green leaves indicate little or no immediate need for N. Yellowish green leaves indicate a relatively higher and urgent need of the crop for N fertilizer. Originally developed for rice, the LCC is also suitable for maize providing farmers with a good diagnostic tool for detecting N deficiency during the season. Following the strategy used in rice, the principles of SSNM for maize were developed through a series of researcher managed on-farm and on-station experiments covering a wide range of bio-physical and socio-economic conditions in Southeast Asia. In the Philippines, on-farm trials were conducted in the three key maize-producing provinces of Isabela, Bukidnon, and Nueva Ecija/Tarlac in 2005-2007. Data from these trials showed that the SSNM concept has significant potential to enhance the productivity and profitability of maize farming in favorable irrigated and rainfed environments. With SSNM, yield increased on average by 1.0 t/ha and net benefit by PhP5,170/ha as compared with the farmer’s practice across all sites and seasons. In August 2008, a new 2-year project in partnership with the Regional Integrated Agricultural Research Centers (RIARCs) commenced with exploratory trials in all 16 regions in the country to develop, evaluate, and disseminate improved nutrient and crop management strategies for maize from 2008 to 2010. First results presented at a review and planning workshop in April 2009 confirmed earlier studies. Based on data from seven regions obtained in 2008/09, used led to a yield advantage of about 1 t/ha compared to the farmers’ practice with even greater yield improvements in reached with refined SSNM strategies to be tested in 2009. Field trials further revealed a lower contribution of Bio-N and organic matter application to nitrogen supply than previously assumed. Based on first season results, Bio-N and applied organic matter (ranging from 500 kg/ha to 5000 kg/ha depending on the source) contributed only about 23 kg N/ha or one bag of urea/ha and not 46 kg N/ha or two bags of urea/ha as previously assumed. Work is underway to provide farmers with options particularly where the risk of crop failure is high (i.e. from flooding or drought). Low-risk strategies (with lower input costs) are under development at sites where farmers face a high risk of crop failure while the standard SSNM strategy would be deployed in the more favorable environments where farmers consistently achieve high yield and profit. Inspite of higher fertilizer prices, there is still hope for profitable yields to Filipino farmers. Site-specific strategies coupled with best management practices promise higher returns through higher yields and effective fertilizer use.
For more information, please contact Mrs. Jocelyn Labios, Agricultural Systems Cluster College of Agriculture, University of the Philippines, College of Agriculture, Los Baños, Laguna, 4031 Tel nos: (+ 63 49 536 4455, fax: + 63 49 536 5282/4455) Email : jdlabios816@yahoo.com
