AGRICULTURAL
Maize production
Calculate your yield potential for upcoming
season for risk management purposes
By Cobus Burger
SGS NviroCrop – Business Manager
Y
ield potential for dryland maize
are influenced by several fac-
tors, of which the following three
aspects can be highlighted as
the main information needed to calculate
crop potential for upcoming season:
Soil type combined with soil moisture
before the season’s plantings start;
Status of top- and subsoil (40 cm
depth) fertility;
Selected plant population.
Soil type explain the variation in
soil properties and it is then used in a
potential model per district or area. The
model was developed and calibrated
over a period of 20 years and is unique to
NviroCrop within the SGS group.
Here follows an example of some soils
with their calculated maize potential, with
the assumption that the soils nutrient sta-
tus is a good average:
Avalon-soil type in the Western Free
State (Hoopstad)
Yellow Apedal soil horizon down to 70 cm
and then a variable water table (Soft plin
tic) to 180 cm.
Profile wet before planting = 8.6 tons/ha
Profile half dry before planting = 5.7
tons/ha
Hutton-soil type in Northwest (Coligny)
Red Brown Apedal soil horizon down to
170 cm and then stone.
Profile wet before planting = 6.6 tons/ha
Profile dry before planting = 3.8 tons/ha
(deep soils is not always a benefit when
profiles are dry before planting. In this
example a not so deep soil profile of
120cm Hutton soil type would have had
a better crop potential for upcoming
season).
Soil fertility change quickly under certain
climatic conditions linked to removal by
the crop, sometimes more than we expect
and may lower your production in difficult
years. The past 5 x years we experienced
some extremely dry seasons during which
our crops root systems more likely fed in
the subsoil (40-50 cm) than in the more
fertile topsoil during wetter seasons. The
2016/17 season we experienced well dis-
tributed rain fall during the second part
of the growing season and the previous
year’s buildup of nutrients had been effec-
tively utilized by the crop.
The maize in general responded well to
this available fertility and above average
yields were the result. The risk is now, that
during a mid-summer drought the pres-
ence of poor subsoil chemistry, reduce
yields. Sampling in top soil well as sub
soil is recommended, to understand the
given risks for upcoming seasons crop.
The following graph deviate from the
standard nutrient removal curve that
everyone knows, to a graph that presents
the percentage of a nutrient that must be
stored in the crop during a specific grow-
ing stage, so that the crop can produce
optimal. The curve is much more insightful
when it comes to understanding why a
crop is producing good or bad yields.
Growth stages of maize vs nutrient uptake curve
V: Vegetative growth stage
16
SENWES SCENARIO | SPRING 2018
R: Reproductive growth stage