Abstract
Cow manure is a good source of phosphorus (P). Here, we investigated whether the amount of P fertilizer can be reduced when cow manure is applied to paddy soil based on growth, P uptake, yield, and soil P status evaluation. Treatments included unfertilized control (CK); manure plus chemical nitrogen (N), potassium (K), and P fertilizer (MNK P); MNK and 75% P (MNK ¾ P); MNK and 50% P (MNK ½ P); MNK and 25% P (MNK ¼ P); and MNK. Manure was applied at the rate of 10 t ha−1 in fresh weight base. The P fertilizer was applied at 34.9 kg P ha−1 as full dose. Treatment with MNK resulted in the same growth, P uptake, and yield as that with the P fertilizer. P uptake and yield did not respond to P input from chemical fertilizer owing to high soil Olsen P levels. Moreover, MNK could maintain soil Olsen P and total P. Manure application resulted in a positive partial P balance. These results suggest that manure application can cut P fertilizer requirements in P-rich soils, while maintaining soil P for optimal rice growth and yield. By using cow manure in rice production, farmers can conserve finite P resources.
Highlights
The application of chemical phosphorus (P) fertilizer has been routine in agronomic practice since the second half of the twentieth century to increase rice productivity in the intensive agricultural system [1,2]
We investigated the growth, P uptake, yield, Olsen P, total soil P, and partial P balance (PPB) of a silage rice field under cow manure application combined with different levels of chemical P fertilizer
Reduction in chemical P fertilizer application rate showed no significant differences in the number of tillers, plant height, and soil-plant analysis development (SPAD) values during the entire cropping season
Summary
The application of chemical phosphorus (P) fertilizer has been routine in agronomic practice since the second half of the twentieth century to increase rice productivity in the intensive agricultural system [1,2]. Japan is one of the countries with no notable reserves of P for future use [8], and all phosphate rocks used in the manufacturing of chemical P fertilizer are imported [9] These sources of phosphate rocks are finite and presumed to last approximately 370 years at the current rates of exploitation [8,10]. In this context, it is possible, as well as essential, to reduce the use of chemical P fertilizer in Japanese paddy fields. Utilization of an alternative P source, such as manure, can be a good management practice to reduce dependance on chemical fertilizers, while maintaining the supply of P to the soil
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