Question: I am working about rice fiels in Madagascar, and i wanted to ask you why there is serveral level of fertelization.

Jennifer Bates answered on 15 Nov 2016:

Hi,

So when you are growing any crop, you want to think about when and how you nourish it, rather than just feeding it all the time or in one big heap, and whether you even need to. Adding too much fertilizer for the sake of it is not good for the soil or water supply and can lead to problems like chemical leaching. Sticking to less chemical-based systems wherever possible to achieve the same grain yield is better, and often less labour intensive.

The International Rice Research Institute (http://irri.org/) recommends that rice farmers use a site-specific nutrient management scheme (http://www.knowledgebank.irri.org/step-by-step-production/growth/soil-fertility) to support their plants, which basically means understanding the needs of the crop in terms of each of its basic nutrients, throughout the growing cycle. That involves firstly working out what is the yield you want to get from your crop and how are you growing it? Then working out what is the existing (indigenous) fertilization cycle – is it sufficient to support your plants without input of extra food from you? What is available from soil, organic additions like leaf litter, crop residues, manure, and irrigation water? And then what is the difference between the hoped for yield and what you can get from the existing nutrient scheme? If it is not enough you need to work out what is lacking? Nitrogen, potassium or phosphorous. You want to make sure you have a balance equal to the amount of grain you want to get out and the time you put in.

And you need to make sure you add them at the right time – so nitrogen, if added, goes in 14 days after transplanting the seedlings or 21 days after sowing them, depending on how you are growing the rice (paddy or upland system?). The easiest way to check it it’s needed is to look at leaf colour! The IRRI provides handy charts. Phosphorus is added near transplantation or sowing, and potassium could be also if only a small amount is used, but if a lot is being used the it is added in two goes, 50% near transplantation/sowing and 50% near to when panicles (the bit that holds the grain) are developing.

Doing it gradually and based on the needs of the plant and soil help not only to protect the environment from too many chemicals being leached into it, but also help the farmer by saving them money (chemicals are expensive), can save time and effort, might stop too many weeds growing on over fertilized and yummy soil, and can protect the plant from over feeding and creating an extra stress on the plant’s systems.

Check out the IRRI website for info on rice agriculture, it will be useful for rice-based projects. 🙂