<strong>and</strong> K; <strong>and</strong> (iii) high fertility fields that showed strong responses to N, P <strong>and</strong> K. Yields with no fertilizer were less than 1 t/ha for all fields, while maximum yields were obtained when all macronutrients were applied. The yield with NPK ranged from 1.3 t/ha in degraded soils to 2.9 t/ha in medium fertility fields to 3.8 t/ha in the high fertility fields. The project results highlight the strong effects of soil fertility variability on maize productivity <strong>and</strong> the need to balance N, P, <strong>and</strong> K supply to optimize maize productivity. Efforts to intensify maize production in northeast Zimbabwe using NPK fertilizers should target the fields in the medium <strong>and</strong> high fertility categories, while long-term strategies to restore productivity in degraded fields will be necessary to make fertilizer use viable. Project results will be used to map the distribution of different fields in north-east Zimbabwe <strong>and</strong> develop decision support tools for use by extension systems to help farmers use fertilizer resources efficiently. Zimbabwe-01 v 62 IPNI Interpretive Summaries
Asia <strong>and</strong> Africa <strong>Group</strong> China Southwest Region: Dr. Shihua Tu Cucumber Yield, Nutrient Use Efficiency, Economic Returns <strong>and</strong> Soil Phosphorus Forms as Affected by Fertilization <strong>and</strong> Irrigation Systems in Yunnan Project Leader: Hong Lifang, Yunnan Academy of Agricultural Sciences Soil <strong>and</strong> Fertilizer <strong>Institute</strong>, Kunming, Yunnan. E-mail: gredbean@163.com Project Cooperator: Fu Libo This ongoing study initiated in 2010 continued to investigate the effects of different fertilizer practices on yield, economic return, <strong>and</strong> nutrient use efficiency of cucumber, one of the most commonly grown vegetables in Yunnan. The goal was to determine optimal fertilizer rates for cucumber production in the region. The experiment consisted of 26 fertilizer treatments involving different rates of N, P, <strong>and</strong> K, each receiving two types of irrigation (drip <strong>and</strong> traditional) <strong>and</strong> replicated three times. In addition, there were two forms of K (KCl <strong>and</strong> K 2 SO 4 ) used in the study to evaluate source differences. Based on the results obtained in 2010, fertilizer rates in 2011 were adjusted to 0, 120, 240, <strong>and</strong> 360 kg of N, 0, 60, 120, <strong>and</strong> 180 kg of P 2 O 5 , <strong>and</strong> 0, 195, 390, <strong>and</strong> 585 kg of K 2 O per hectare, of which rates of N <strong>and</strong> P were lowered <strong>and</strong> K was raised, <strong>and</strong> applied several times in a 10-day interval starting from seeding. Results showed that 2011 cucumber yields were higher than those in 2010, especially for drip irrigation. Drip irrigation increased cucumber yield by 7,960 to 11,380 kg/ha (20 to 30%) <strong>and</strong> saved water by 563 m 3 / ha (40%) compared to the traditional irrigation. The optimal (OPT) fertilizer treatment tested was 240-120- 390 kg N-P 2 O 5 -K 2 O/ha under both irrigation systems in 2011, a reduction of 60 kg N/ha <strong>and</strong> 30 kg P 2 O 5 /ha, but an increase of 30 kg K 2 O/ha compared to rates used in 2010. The net income of OPT was USD 14,787 for drip irrigation <strong>and</strong> USD 11,774 for traditional irrigation. The agronomic efficiencies of N, P, <strong>and</strong> K fertilizers were 45, 53, <strong>and</strong> 36 kg cucumber/kg nutrient under drip irrigation <strong>and</strong> 36, 46, <strong>and</strong> 31 under the traditional irrigation, respectively. Potassium chloride produced higher cucumber yield than K 2 SO 4 at all K rates in 2010, but this was reversed in 2011, possibly due to continued omission of S over for two years. This study revealed that in addition to meeting the proper 4R management of the crop, other agronomic practices such as proper irrigation method were crucial to improving crop yield <strong>and</strong> fertilizer use efficiency. Yunnan-BFDP-08 Effect of Balanced Fertilizers on Papaya Yield <strong>and</strong> Quality in Guangxi Project Leader: Tan Hongwei, Guangxi Academy of Agricultural Sciences Soil <strong>and</strong> Fertilizer, Nanning, Guangxi. E-mail: hwtan@public.nn.gx.cn Project Cooperator: Zhou Liuqiang This study, initiated in 2010, continued to evaluate the effects of different fertilizer treatments on fruit yield <strong>and</strong> quality of papaya grown in Nanning City, Guangxi. There were seven treatments including: an optimal treatment (OPT) <strong>and</strong> treatments individually omitting N, P, K, Mg, B, <strong>and</strong> Zn within the OPT. Since papaya response to Mo was insignificant in the previous year, it was omitted from this year’s design. The OPT treatment remained the same as set in 2010 at 900-190-960 kg N-P 2 O 5 -K 2 O/ha, plus 130 kg MgO/ha, 4.0 kg borax/ha, <strong>and</strong> 4.0 kg zinc sulfate/ha. Papaya yields significantly responded to N, P, <strong>and</strong> K application at two sites in spite of the considerable difference in their productivity. Yields were reduced by 18.6 t/ha (-41.6%), 8.6 t/ha (-19.1%), <strong>and</strong> 5.7 t/ha (-12.6%) with omission of N, P, or K, respectively. Omission of Mg or Zn reduced papaya yield by 3.4% <strong>and</strong> to 4.5%, respectively, while omission of B had little effect on yield, implying that the critical value for B needs to be adjusted as soil testing did indicate existing deficiencies. Agronomic efficiencies for different fertilizer application were 20.7 kg fruit/kg N; 44.8 kg fruit/kg P 2 O 5 ; 5.9 kg fruit/kg K 2 O; 12 kg fruit/kg MgO; 2,200 kg fruit/kg Zn, <strong>and</strong> 1,300 kg fruit/kg B, respectively. Based on the two-year results of OPT treatments, 1,000 kg of papaya fruit requires 3.3 to 4.2 kg of N, 1.3 to 1.8 kg of P 2 O 5 , 9.0 to 11.1 kg of K 2 O, 1.4 to 1.8 kg of MgO, 7.4 to 9.8 g of Zn, 2.7 to 3.6 g of B, respectively. Guangxi-BFDP-08 IPNI Interpretive Summaries 63
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