optApp: Compute the optimal fertilizer application for a crop and...

In Rquefts: Quantitative Evaluation of the Native Fertility of Tropical Soils

Compute the optimal fertilizer application for a crop and location.

Description

Compute the optimal fertilizer application given a quefts model, the value of the crop product, and available fertilizer products, and their prices.

All computations are per ha and all prices should be in the same currency. Note that the value of the crop must be specified on a dry matter basis.

Usage

optApp(qm, fertilizers, dm_crop_value, min_use=0, max_inv=Inf)

Arguments

qm	A quefts model
fertilizers	data.frame with fertilizer products, NPK content and prices (see examples). There must be at least these five variables: "name", "N", "P", "K" (nutrient content as percentage) and "price_kg" (price per kg of the product
dm_crop_value	numeric. The value of the crop product per kg dry matter (!). That is you need to divide the actual value with the fraction dry matter content. E.g. divide by ~.85 for grains and ~0.35 for cassava
min_use	numeric. The minimum amount allowed for a product, to avoid very low application rates
max_inv	positive number. The maximum allowed total investment

Examples

# fertilizer product list
fert <- fertilizers()
# shortening some of the names for display
fert[,2] = substr(fert[,2], 1, 20)
# contents are expressed as a percentage.
ferts <- fert[c(8,15:17), 2:5] 
ferts$price_kg <- c(1, 1.5, 1.25, 1.5)

soiltype <- quefts_soil()
barley <- quefts_crop("Barley")
fertilizer <- list(N=0, P=0, K=0)
att_yield <- list(leaf_att=2200, stem_att=2700, store_att=4800, SeasonLength=110)
q <- quefts(soiltype, barley, fertilizer, att_yield)

x <- optApp(q, ferts, dm_crop_value=.25)
x
x$fertilizer

y <- optApp(q, ferts, dm_crop_value=.75)
y
y$fertilizer

Rquefts documentation built on March 17, 2026, 5:07 p.m.