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Interpretive Summaries:
2005 - Effect of Balanced Fertilization for Fish Grasses in Hubei
2004 - Effect of Balance Fertilization on Fish Grasses in Hubei
2003 - Effect of Balanced Fertilization on Fish Grasses in Hubei
Effect of Balanced Fertilization on Fish Grasses in Hubei, 2005
Fish grass is an important forage for fish-pond production systems with an estimated 70,000 ha planted in the Jianghan Plain of Hubei and 1,500,000 ha planted in southern China. Still, a large gap exists between supply and demand. Yield improvements will have a direct effect on total fish production. Grass production is still new to farmers and they lack knowledge concerning fertilization. A recent investigation found that nitrogen (N) fertilization rates in farmers' fields are commonly as high as 600 kg N/ha, while potassium (K) rates range between 75 to 150 kg/ha. Farmers generally depend on N alone, but this results in low yields and poor efficiencies for both farming and fisheries. Four field experiments and two balanced fertilization [N, phosphorus (P), K] demonstrations were carried out in 2005.
At Honghu County, a - K treatment supplying 270-180 kg N-P2O5/ha produced 56 t/ha of sorghum sudanense. Further supplementation with either 180 kg K2O/ha and 360 kg K2O/ha produced an additional 14.9 t/ha and 14.0 t/ha, and increased net profit by US$384/ha and US$288/ha, respectively. In Jiangxia County, six treatments were compared against farmer practice (FP) of applying 525-45-52.5 kg N-P2O5-K2O/ha in sorghum sudanense. A treatment supplying an additional 138 kg K2O/ha increased yield by 5 t/ha, or 9.0%, and returned US$42/ha more profit. Compared against a - K treatment providing 450-150 kg N-P2O5/ha and yielding 65.3 t/ha, further K supplementation, supplied as either potassium chloride (KCl), potassium sulfate (K2SO4), or K-Mag® (K2SO4 · 2MgSO4) at 240 kg K2O/ha increased yield (and profit) by 8.5 t/ha (US$160.5/ha), 6.7 t/ha (US$72.7/ha), and 12 t/ha (US$172/ha), respectively.
In Honghu County, compared to the zero-fertilization check yield of 20.2 t/ha, application of 180 kg N/ha, 180-135 kg N-P2O5/ha, 180-180 kg N-K2O/ha, and 180-135-180 kg N-P2O5-K2O/ha increased ryegrass yields (net profits) by 14.0 t/ha (US$133/ha), 31.8 t/ha (US$332/ha), 22.2 t/ha (US$199/ha), and 41.0 t/ha (US$413/ha), respectively. If compared to the N-only treatment which produced 34.3 t/ha, P, K, and PK increased yield by 17.8 t/ha, 8.2 t/ha, and 27.0 t/ha, respectively. In Jiangxia County, ryegrass yield changed greatly due to fertilization. Only 10 t/ha was achieved with - N treatments and not more than 60 t/ha was produced with - P or - K treatments. The NPK treatment providing 375-135-120 kg N-P2O5-K2O/ha produced a high yield of 76.9 t/ha. The most economic NPK treatment for ryegrass was 320-135-180 kg/ha.
There are 100,000 ha of forage lands used for fish production in Hubei and 70% are located in the Jianghan Plain. According to this research, at least 50 kg P2O5 and 120 kg K2O/ha should be applied to these fields. If more farmers use the recommendation, about 3,500 t P2O5 and 8,400 K2O is required for Jianghan Plain forage lands, which would increase farmers returns by US$28 million. Hubei-22
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