Agriculture Reference
In-Depth Information
Los Baños (CES-UPLB) was used, whereas the experiment in the 2010
WS and the 2010/11 DS was conducted at the Experimental Station of
the International Rice Research Institute (IRRI) in Los Baños (ES-IRRI).
Both experimental sites were located in close vicinity (about 1 km apart)
in Laguna Province, Philippines (14°11' North, 121°15' East, 21 masl),
in a typical lowland rice production area with the dominant soil type “an-
thraquic Gleysols” [26]. Detailed soil characteristics were analyzed only
for the field at ES-IRRI (Table 1) but the soil at CES-UPLB was similar.
The soil at both sites had a fine texture (clayey loam) and a high cation
exchange capacity (CEC). Topsoil pH values at CES-UPLB in the 2009
DS and WS were 6.9 and 6.8, respectively, while pH values of 6.9 (2010
WS) and 6.5 (2011 DS) were observed at the ES-IRRI site. The soil or-
ganic carbon concentrations at both farms were relatively high, ranging
between 1.5% and 1.9%. Related to this, organic N concentrations were
also high at both farms (0.15-0.27%). The high soil organic matter content
also caused high P availability as indicated by high Olsen P values, which
were far above the critical low level of 10-15 mg·kg
−1
[27]. Similarly, the
exchangeable K was adequate for both experimental sites at the start of the
cropping seasons [27].
TABLE 2:
Inorganic fertilizer treatments in all four experimental seasons as ratio of the
recommended rate (RR) and as actual nutrients applied in the dry and wet season.
Fertilizer Rate
Unit
Dry Season
Wet Season
0% RR
N-P
2
O
5
-K
2
O in kg·ha
−1
0-0-0
0-0-0
25% RR
N-P
2
O
5
-K
2
O in kg·ha
−1
30-15-15
22.5-7.5-7.5
50% RR
N-P
2
O
5
-K
2
O in kg·ha
−1
60-30-30
45-15-15
100% RR
N-P
2
O
5
-K
2
O in kg·ha
−1
120-60-60
90-30-30
or
0% RR
N-P-K in kg·ha
−1
0-0-0
0-0-0
25% RR
N-P-K in kg·ha
−1
30-7-13
22.5-3-6
50% RR
N-P-K in kg·ha
−1
60-13-25
45-7-13
100% RR
N-P-K in kg·ha
−1
120-26-50
90-13-25
