Co-benefits of nutrient management tailored to smallholder agriculture. Global Food Security: 30, 100570
Chivenge, P., Saito, K., Bunquin, M.A., Sharma, S., Dobermann, A. 2021.
Summary by Dobermann, A.
Nearly 25 years ago IFA, along with other public and private sector funders, started supporting research on a new approach for site-specific nutrient management (SSNM), which, in essence, is a form of 'precision farming' for smallholder farmers. Over time, digital decision tools for SSNM were developed by several organizations for rice, wheat, maize, cassava and other crops in Asia and Africa. This paper summarizes the work done since the mid-1990s. It shows very robust performance benefits across different crops and environments. On average, using SSNM, yields of rice, wheat and maize increased by 12%, profits by 15% and agronomic nitrogen use efficiency by 40%. Compared to current farmers practices, 10% less nitrogen fertilizer, better timing of N application and more balanced nutrition with potassium were required to achieve that. The biggest challenge has been to scale this approach up from thousands of farmers to millions of smallholder farmers. This will require wider uptake by the private sectors as well. Opportunities exist to, based on the existing SSNM principles, databases and models, develop suitable farmer advisory solutions. The Consortium for Precision Crop Nutrition, https://www.precisioncropnutrition.net/, provides a new platform for more open innovation and public-private sector collaboration on SSNM. IFA members interested in that area are welcome to join.
Classic Plant Nutrition Paper
The quantitative mineral nutrient requirements of plants. Plant Physiology 11:749–764
Macy, P. 1936.
Summary by Dobermann, A.
Although the general needs of plants for various mineral elements had been recognized since the early- 19th century, no method had been accepted for measuring the quantitative mineral nutrient requirements of plants. Working at Cornell University, Paul Macy in this elegant paper developed a relationship between the percentage content of a nutrient in a plant and the sufficiency of the nutrient for growth. He didn’t really invent that concept, but he brought it forward hugely. Others before him had already proposed that there is a certain ‘sufficiency’ of a nutrient, but they also found that responses to nutrients added dependent on many different factors. The central idea in his paper is that there is a critical percentage of each nutrient in each kind of plant, above which there is luxury consumption and below which there is poverty adjustment, which is almost proportional to the deficiency until a minimum percentage is reached. He confirms this hypothesis using data from the literature and by conducting experiments with nitrogen in barley. Extreme effects of other factors on the yield and on the nitrogen content of the straw had no effect on that relationship. He concludes that the critical nutrient composition of a plant is an "ideal" but inherent characteristic of the plant, and that this concept could be used to determine fertilizer needs of particular crops on particular soils under the particular local conditions. Discoveries such as this one have laid the foundation for what we nowadays call precision farming, or site-specific nutrient management.