[EN] 03. IRRI Agronomy Challenge 2: First Fertilizer Application

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Description:

Achim Dobermann, deputy director general for research at the International Rice Research Institute (IRRI; http://irri.org), and Leigh Vial, head of IRRI's experiment station, begin IRRI Agronomy Challenge II. It is the continuation of a special project in which they demonstrate how to grow a productive rice crop in a 25 x 100-meter field on IRRI's research farm.

Here, Achim makes the first fertilizer application about 1 week after transplanting.

Achim's commentary:

28 December: I came back about a week after planting to apply the first dose of fertilizer. We went through the basics of that in our post last year.

We found that using the Nutrient Manager decision tool made this all very easy because answering the series of simple questions about our field and the previous and planned management practices took only about 5 minutes. Most importantly, it resulted in an "actionable" recommendation we could easily implement. So, what's going to be different this time? Actually, not that much.

In terms of IT technology, we have an exciting new version of Nutrient Manager for Rice available in the Philippines (version 2.2.), which has been re-programmed in HTML 5 language. The main advantage of that is that the software has become device-independent, i.e., it runs in the "cloud" on any hardware, including desktops, laptops, tablets, or any of the available smartphones. Soon, it will also receive further extensions in functions towards making other critical crop management decisions.

In terms of agronomy, we have to consider that this time we have planted an inbred and a hybrid variety. That has three major implications for nutrient management: (i) the hybrid should have a higher yield potential and thus also higher attainable yield than an inbred cultivar; hence it will need some more nutrients too, (ii) previous research has shown that to fully exploit the higher yield potential a hybrid is more likely to benefit from a small late N application at heading stage than an inbred, and (iii) the growth duration is different and hybrids may also have more early vigor than inbred, affecting the timing of fertilizer applications.

The hybrid we have chosen, Mestiso 26 (IR82372H), is expected to mature about 1 week earlier than the inbred NSIC Rc302 (IR05A272). So, I ran the Nutrient Manager separately for each of the two cultivars, assuming a target yield of about 7 t/ha for the inbred (about 70-80% of yield potential for an average dry season climate at Los Baños) and 7.5 t/ha for the hybrid.

In practical terms, the differences in timing of applications are quite small, so we'll aim to do it all on the same days for both varieties (the late date range of the hybrid, which is close to the early date range of the inbred). In terms of product choices, we'll keep things simple an go with 14-14-14 compound fertilizer for the basal (early) application, which translates into about 4 bags/ha for the inbred and 4½ bags/ha for the hybrid.

It took me about half an hour to complete this first broadcast application, although I had to do an extra pass on the hybrid to apply a little more fertilizer that had been left over.

I realize, more and more, that spreading fertilizer by hand on the soil surface is not going to help us much with increasing fertilizer efficiency in the future. At this early stage, the seedlings are barely growing and cannot take up nutrients quickly. Moreover, the machine we used planted at 30-cm row spacing, leaving a lot of empty surface space on which the fertilizer granules fell.

I wish we had the possibility to place it close to the rows of young plants, into the soil, but we don't have such a machine yet. Adding fertilizer boxes to the mechanical planter would also add more weight to it, complicating the planting operation. I'm dreaming that someday we'll have a small- or medium-size crop care machine that can do more precise applications of fertilizers and pesticides in row-planted rice crops, perhaps even with precision guidance.