Agriculture Reference
In-Depth Information
information includes nitrogen content, phosphorus content, potassium content,
and trace elements. The physical and chemical indexes in soil includes water con-
tent, pH, saline and alkaline, organic matter, electric conductivity, and compact-
ness. Normally, traditional chemical methods are applied to detect these physical
and chemical indexes, which are costly, time consuming, laborious, and unsuitable
for fast and rapid detection. The time-domain reflectometry (TDR) method and
hydroprobe moisture instrument can be used for the detection of soil water content.
Recently, visible and NIR spectroscopy were applied in soil parameter detection. Li
(2003) studied soil moisture, soil organic matter (SOM), electric conductivity (EC),
NO
3
-N, and pH using visible spectroscopy. Yuan et al. (2009) studied total nitrogen
content and total phosphorus content using NIR spectroscopy. He et al. (2007) stud-
ied the potential of NIR spectroscopy to estimate N, P, K, organic matter (OM), and
pH content in a loamy mixed soil. The correlation coefficient (
r
) between measured
and predicted values of N, OM, and pH was 0.93, 0.93, and 0.91, respectively, and
the standard error of prediction (SEP) was 3.28, 0.06, and 0.07, respectively, which
showed that NIR had the potential to accurately predict these constituents in this
soil. Unfortunately, it also showed that NIR was not a good tool for P and K predic-
tion, with
r
= 0.47 and 0.68, and SEP = 33.70 and 26.54, respectively. Sinfield et al.
(2010) suggested that biosensors were more suitable for phosphorus content detec-
tion, and ion-selective electrode or ion-selective field-effect transistors were more
suitable for potassium content detection. Qiu et al. (2003) developed the soil water
content detection instrument with GPS systems. Wang et al. (2003) developed a soil
electric conductivity detection system; Tang et al. (2007) applied spectroscopic tech-
niques to develop a soil organic matter measuring instrument.
9.3 NUTRITIONMANAGEMENT
Nutrition management include soil and crop sampling, aerial photography for nutri-
tion maps, nutrition disputation based on GIS, and automation of operation of nutri-
tion management. An important outcome is to perceive the potential benefits of soil
and crop management by zones within fields rather than whole fields for increased
profitability and environmental protection. At the same time, GIS and GPS became
available and made possible the acquisition, processing, and utilization of spatial
field data as well as the development of a new kind of farm machinery with com-
puterized controllers and sensors. The usual methods used for sample sampling and
management, nutrition distribution based on GIS, and automations were introduced
for the understanding of nutrition management (Wang, 2011).
9.3.1 S
AMPLING
M
ETHOD
AND
M
ANAGEMENT
For soil sample management, the most commonly used method is grid sampling
(Robert, 2002). Akridge and Whipker (1999) indicated that 36% of dealers/consul-
tants used a sampling grid size greater than 1 ha for lower costs. However, many
studies indicate that the resulting nutrient status maps provide inaccurate spatial
nutrient needs if the sampling size is greater than 0.4 to 1 ha (Mallarino and Wittry,
2000). Another common practice in the Midwest for selecting soil sampling sites,
