| dc.description.abstract | Evaluation of fertility status of the soil based on its capacity to supply
nutrients can help to improve productivity and increase fertilizer efficiency. Soil
testing is a method of evaluation of soil fertility status in order to know the level
of nutrient availability for a certain crop in a given soil type. Soil test phosphorus
(STP) is a measure of plant available phosphorus (P) in a soil extracted by various
extractant later the STP calibrated with crop response in order to determine P
fertilizer requirement. The basic aim of soil testing is to assess nutrient status,
thereby identifying current and potential need for fertilization. In Lembang
district, Indonesia Andisol covers appreciable area, and defined taxonomically its
andic properties and contains high allophanic materials. However, in volcanic ash
soil P is strongly sorbed by non-crystalline aluminum and iron materials, it lowers
P availability for plant uptake. Hence, inadequate P concentration in soil can
restrain plant growth in the district and low P fertilizer efficiency reduces farm
profitability.
This study, soil testing to establish P critical level for potato (Solanum
Tuberosum L.) in Andisol was conducted in Lembang district, west Java,
Indonesia in greenhouse from February – June 2018 at Indonesian Agricultural
Technologies Research Center (BPTP) in Lembang. In the study area farmers
grow intensively agricultural crops including potato. However, the farmers apply
blanket method of P fertilizer to grow potato is commonly practiced. The blanket
method of fertilizer application does not consider the spatial and temporal soil
fertility variations and farmers apply the same P fertilizer rate to their fields
regardless of fertility difference. As a result profitability of potato production can
be restrained by low P fertilizer efficiency. Therefore, the objective of this study
was soil testing to establish P critical level for potato in Andisol of Lembang by
graphical approach in order to increase P fertilizer use efficiency. Hence, soil P
tests are useful to identify soils deficient in P and provide a guide to determine P
requirement as to the magnitude of the crop's response to applied P. In turn, it
allows for the growers more efficient utilization of P fertilizer.
For the selection of representative soil across the area 30 soil samples (0-
15cm depth) were collected before the onset of the trial. Selected soil physical and
chemical properties such as soil texture, organic carbon, Cation Exchange
Capacity, exchangeable basic cations, total nitrogen, and available P were
analyzed by respective methods. Soil test P was extracted by Olsen extraction
method and the soil categorized in to low P (soils with P concentration <25 mg
kg-1) and high P (Soils with P concentration >46 mg kg-1) using standard rating of
Olsen extraction method. The number of treatments were 7 rates of phosphorus
fertilizer (0, 25, 50, 75, 100, 125, and 150 kg P ha-1), replicated thrice for both low
P and high P soil. Total number of pots were 42 (21 pots for low P soil and 21
pots for high P soil). After three weeks of planting soil samples taken from each
pots (5cm depth) in order to analyze Olsen extractable P.
Potato tuber yield was harvested after three months of planting. The
analysis of variance of the experiment result indicated that there were significant
(P < 0.05) responses of tuber yield to P fertilizer rates. Similarly, extractable P
concentration extracted after three weeks of planting by using Olsen extraction
method were also significantly differed (P < 0.05) among P fertilizer rates. The
correlation between relative tuber yield response and soil P measured with Olsen
method was indicated that the critical level of extractable P concentration for
potato using data of soil test P and corresponding relative tuber yield for all
treatments, tested by Olsen extraction methods 68.8 mg kg-1 and 191 mg kg-1for
low P and high P soils respectively determined by Cate-Nelson graphical method.
Result showed that the increase in soil P response to P fertilizer application was
linear up to 75 kg P ha-1 on low P soil and the increase in soil P response to P
fertilizer application was linear up to 50 kg P ha-1 on high P soil, but the increase
in yield was not significantly different beyond 75 and 50 kg P ha-1rate for low and
high P soils respectively. The highest tuber yield (17125 kg ha-1) was recorded
from 50 kg P ha-1 with mean relative yield response of about 100% on high P soil
and (16921 kg ha-1) with mean relative yield response about 100% on low P soil.
According to the results it can be concluded that potato tuber yield
responded to P fertilizer rate significantly different as compared with yield
obtained without P fertilizer on Andisol of the study area. The results of this
experiment clearly revealed the importance of soil test based P fertilizer
application for improving yield of potato and P fertilizer efficiency on Andisol of
Lembang district, Indonesia. In turn, farmer’s economic return can be increased.
Extractable P concentration extracted after three weeks of planting by using Olsen
extraction method was also significantly differed among P fertilizer rates. Using
the Cate and Nelson graphical method the critical level of soil extractable P
concentration for potato production was on low P soil 68.8 mg kg-1 and on high P
soil 191 mg kg-1 by Olsen extraction method. At soil test P values less these
critical values of extractable P, P fertilizer should be applied to increase potato
tuber yield. | id |
