Summary
Integrated soil fertility management (ISFM) aims at the optimal and sustainable use of soil nutrient reserves,
mineral fertilizers and organic amendments. We explain in this reference how to calculate mineral and organic
IHUWLOL]HUQHHGVWRREWDLQWDUJHWLHOGVDVDIXQFWLRQRIWKHVRLOQXWULHQWVXSSOLQJFDSDFLWPDLQOQLWURJHQ1
phosphorus, P; potassium, K) and taking into account yield potential (determined by cultivar choice, sowing
GDWHDQGFOLPDWH$QDOVLVRIVRLOIHUWLOLWXVLQJODERUDWRUSURFHGXUHVLVVHOGRPSRVVLEOHLQIDUPHUV¶¿HOGV
and the relation between such analyses and rice growth is often poor, especially for nitrogen. This reference
offers another method to determine the soil nutrient-supplying capacity. The rice yield from a mini-plot, with
JRRG VRLOIHUWLOLWPDQDJHPHQW EXWZLWKRXW DSSOLFDWLRQ RI RQH QXWULHQW IRU LQVWDQFHZLWKRXW13 RU. LV
FRQVLGHUHGDVDQLQGLFDWRURIWKHFDSDFLWRIWKHVRLOWRVXSSOWKDWµPLVVLQJQXWULHQW¶
7RLQFUHDVHLHOGEWKDQXWULHQWXSWDNHDWPDWXULWQHHGVWRLQFUHDVHENJ1KDNJ32
O5/ha and
18 kg K2
2KD$ZHOOEDODQFHGIHUWLOL]DWLRQWKXVUHTXLUHVDQDSSOLFDWLRQRINJ1KDNJ32
O5/ha and 60
kg K2
2KDWRLQFUHDVHLHOGEWKDEDVHGRQDUHFRYHUUDWHRIDSSOLHGIHUWLOL]HURIIRU1DQG.DQG
of 20% for P. The recovery rate is the percentage of fertilizer effectively absorbed by the plant as compared
to the quantity applied. These relations are approximate and only valid for yields not exceeding 70 to 80%
of the potential yield. For higher yield targets, more nutrients have to be applied to get the same return, and
WKLVLVQRWXVXDOOFRVWHIIHFWLYH1LWURJHQORVVHVDUHLUUHYHUVLEOHWKXVLWLVYHULPSRUWDQWWRLQFUHDVHWKH
recovery rate of this nutrient. The recovery rate of nitrogen is strongly related to crop management. This
reference provides instructions to help increase this recovery rate. For P and K, losses are much less (P and
K are absorbed by the soil), and the residual effect of the fertilizer applied is often visible several years after
application. Organic fertilizer can, to a certain extent, replace mineral fertilizers, but large quantities need to be
applied as organic fertilizers have a low nutrient content. However, using both mineral fertilizers and organic
DPHQGPHQWVRIWHQKDVVQHUJLVWLFHIIHFWVLQFUHDVLQJWKHVRLO¶VQXWULHQWVXSSOLQJFDSDFLWLQWKHORQJWHUP
and in some cases increasing the recovery rate of mineral fertilizer nutrients.
Soil fertility depends on the soil’s origin (alluvial soils, soils derived from different types of parent
URFNHWFLWVWH[WXUHVWUXFWXUHDQGRUJDQLFPDWWHUFRQW