Rquefts (version 1.2-3)

revSupply: Estimate soil nutrients supply

Description

Estimate the apparent base (unfertilized) soil supply of N, P and K based on nutrient omission trial data and a "reverse" QUEFTS approach. The apparent supply is found with optimization.

Usage

revSupply(obs, crop, soil, Ya, leaf_ratio, stem_ratio, SeasonLength = 120, ...)

Value

numeric vector with the N, P, and K supply in kg/ha

Arguments

obs

data.frame with observed data from a nutrient omission trial. It must have these four columns: "N", "P", "K" and "Y"; that give the N, P, and K fertilizer application and the crop yield in kg/ha

Ya

numeric. Attainable yield

soil

list with named soil parameters. See quefts_soil

crop

list with named crop parameters. See quefts_crop

leaf_ratio

positive numeric (typically between 0 and 1) indicating the leaf weight relative to the storage organ weight. For example: 0.46 for maize, 0.17 for potato, and 0.18 for rice

stem_ratio

positive numeric (typically between 0 and 1) indicating the stem weight relative to the storage organ weight, For example: 0.56 for maize, 0.14 for potato, and 0.67 for rice

SeasonLength

positive integer

...

additional arguments supplied to optim

References

?

Examples

set.seed(777)
trial_data <- data.frame(treat = c("CON", "NPK", "NPK", "PK", "NK", "NP"),
                  N = c(0, 120, 120, 0, 120, 120),
                  P = c(0, 30, 30, 30, 0, 30),
                  K = c(0, 60, 60, 60, 60, 0),
                  Y = c(2000, 6000, 6000, 2500, 4500, 5500) + rnorm(6, 0, 500))
Ya <- max(trial_data$Y) + 1000
crop <- quefts_crop("Potato")
soil <- quefts_soil()

revSupply(trial_data, crop, soil, Ya, leaf_ratio=.17, stem_ratio=.14)