Americas and Oceania Group - International Plant Nutrition Institute

ha for RU and at 105 kg N/ha (50% of the full N rate) for CRU. Agronomic efficiency of both CRU and RU
decreased with increasing increments of N application, ranging from 9.5 to 12.6 kg kernels/kg N for CRU and
3.1 to 8.4 kg kernels/kg N for RU. Nevertheless, some of the CRU granules remained intact or with partial
N release at harvest time due to protection of the plastic mulch on the soil surface from rainwater infiltration,
resulting in inefficient use of CRU by maize and underestimated maize response. Thus, even in this humid
climate, the right method of CRU placement needs further study to safeguard complete N release from the
coating during the maize growing season. Yunnan - BFDP -11
Response of Winter Rapeseed to Controlled-Release Urea in Sichuan
Project Leader: Sun Xifa, Sichuan Agricultural Sciences and Chongqing Ag-tech Extension Center Soil and Fertilizer
Institute, Sichuan, Chongqing. E-mail: sunxifa@163.com
Project Cooperators: Wenqiang Feng and Yusheng Qin
The objective of this field experiment was to evaluate the response of winter rapeseed to controlled-release
urea (CRU) under rain-fed conditions in Sichuan Basin. The deliverables from the project will be the impact
on crop yield, N uptake, and economic benefit. The field experiment in 2011 was conducted on an alluvial
loam soil with four N rates (0, 90, 135, and 180 kg N/ha) and three replications. Each rate of N was tested
as paired CRU and regular urea (RU) treatments for strict comparison of CRU effect. Two split application
treatments were included, one with 40% RU basal at transplanting and 60% RU top dress one-month after
transplanting, and the second split used 40% RU and 60% CRU both applied at transplanting. All treatments
received equal rates of P and K fertilizers that were used as basal application.
Results showed that at the same N rate, the RU treatment always produced much higher or significantly
higher rapeseed yield than the CRU treatments. The RU 40%+CRU 60% applied as basal application
achieved the highest seed yield among all the treatments. Rapeseed yield increased with an increase in N
rate and leveled off when N rate was above 135 kg/ha for RU, but with no yield drop for CRU. This implies
that under conditions without irrigation, a dry growing season (accumulative precipitation of 110 mm, but
unevenly distributed in 7 months) severely restricted N release from the CRU and thus, rapeseed growth.
As a result, CRU could not supply sufficient N to rapeseed no matter what N rates there were in dry season.
Accordingly, all the RU treatments had higher N recovery by 4 to 10% and agronomic efficiency by 1 to 2 kg
seed/kg N compared with its counterpart CRU treatments. The result further suggested that though CRU is an
excellent N fertilizer in wet or irrigation conditions, caution should be taken when it is used under dry season
with no irrigation. Sichuan-BFDP-08
Right Fertilizer Timing Promoted Sugarcane Yields in Guangxi
Project Leader: Hongwei Tan, Guangxi Academy of Agricultural Sciences Soil and Fertilizer Institute, Nanning,
Guangxi. E-mail: hwtan@public.nn.gx.cn
Project Cooperators: Liuqiang Zhou and Rulin Xie
In order to showcase the effect of right fertilizer time on sugarcane yields to growers, industry, technicians,
and fertilizer retailers, educational field trials were conducted in a sugarcane base located in Laibin, Guangxi
in 2011. The field trials consisted of four treatments with different combinations of fertilizer timing: basal
+ topdress at tillering stage, basal + topdress at cane elongation stage, basal + topdress at tillering stage and
at cane elongation stage, and basal + topdress at seedling stage and at cane elongation stage (the farmers’
practice). All the treatments used the same source and rates of fertilizers: 450-135-320 kg of N-P 2 O 5 -K 2 O/ha.
The trials were used as an on-site training site for the above mentioned groups in 2011.
Results showed that the treatment of basal + topdress at tillering stage and at cane elongation stage
produced the highest cane yield, 3.7 to 6.0 t/ha (7.8 to 8.5%) more than the farmers’ practice. Net income
was increased by USD 468 to 496/ha (7.7 to 8.5%). The other two treatments also increased cane yields and
net income compared to the farmers’ practice, but significantly less than the treatment of basal + topdress
at tillering stage and at cane elongation stage. Thus, this treatment can be considered as the best timing
combination for sugarcane production in Laibin region. The trials convinced local farmers that the effect of
properly timing of fertilizers can generate significant improvements in sugarcane yield and net income by
using the same fertilizer source and application rates. Guangxi-BFDP-11
66 IPNI Interpretive Summaries