Americas and Oceania Group - International Plant Nutrition Institute

Results showed that mulching the soil with wheat straw or plastic film significantly increased corn yield
by 6.4% or 7.2 % compared to the no mulch treatment. This further confirmed that any methods that could
conserve more soil moisture and prevent soil erosion and nutrient losses could produce more corn yield on the
non-irrigated sloping lands.
Among the four N sources without surface mulch, CRU produced the highest corn yield, followed by urea,
calcium nitrate, and ABC. When combined with surface mulch, all N sources significantly enhanced corn
yields. It is of interest that CRU and ABC were equally superior to urea and calcium nitrate on corn yields.
Ammonium bicarbonate use under wheat straw mulch slightly reduced corn yield compared to ABC under
plastic mulch. Ammonium bicarbonate, an inferior N source, once dominated China’s N fertilizer market,
but today is of least importance, performed the best under surface mulch, indicating that different agronomic
practices can affect the performance of a fertilizer considerably. By further analyzing amounts of soil erosion
and nutrient losses caused by different treatments, we determined that mulching treatments significantly
reduced nutrient losses through reduced soil erosion (44 to 58%) and reduced leaching or surface runoff (4.1
to 20.3 mm), enhanced N uptake by corn and finally corn yields, the same trend reported in the previous
years. Sichuan-BFDP-09
Response of Chinese Cabbage to Different Timings of Fertilizer Application in Chongqing
Project Leader: Zhengyin Wang, Southwest University Agricultural Resources and Environment Beibei District
Chongqing, Chongqing. E-mail: wang_zhengyin@163.com
Traditionally, P and K fertilizers are used as basal application to most crops, if not all. It is unclear what
extra benefit would accrue when these two fertilizer are used in split applications at different growth stages of
a crop. Thus, this study aimed to investigate the effect of split application of P and K along with N fertilizers
on yield and quality of Chinese cabbage in Chongqing, China in 2011. There were six fertilizer treatments
combining equal rates, but different timings, of N as urea, P as mono-potassium phosphate, and K as KCl
at 300-90-150 kg N-P 2 O 5 -K 2 O/ha. The six treatments included: (1) the conventional timing of fertilizer
application (i.e. 100% of P and K fertilizers applied basally, N fertilizer split between basal and top dressing
at rosette, cupping, and the fast growing stage; (2) N and P fertilizers split using the above mentioned stages
and only K fertilizer was applied basally; (3) N and K fertilizers were split as above and only P fertilizer
applied basally; (4-6) all N, P, and K fertilizers were split in above mentioned stages, but with three different
allocation percentages.
Results showed that at the same N, P, and K fertilizer rates, the conventional timing of fertilizer application
produced the least cabbage yield, while the treatment splitting N, P, and K fertilizers basally at 20% N, 30%
P 2 O 5 , 30% K 2 O, and topdressing only at rosette stage at 40% N 40%, 30% P 2 O 5 , 30% K 2 O and cupping stage
at 40% N, 40% P 2 O 5 , 40% K 2 O produced significantly higher yield than the other treatments. All the other
treatments had the similar yield level with non-significant differences. Further, all the splitting treatments
enhanced quality parameters by 2 to 5% for vitamin C, 13 to 33% for reducing sugar, 3 to 28% for amino
acids, and 0 to 26 % of reduction for nitrate N compared to the conventional timing of fertilization. The
highest yield treatment also improved the cabbage quality by enhancing contents of vitamin C and reducing
nitrate N in the leaf head, slightly decreasing reducing sugar and amino acids compared to the other splitting
treatments. Chongqing-BFDP-11-01
Response of Maize under Plastic Mulch to Controlled Release Urea (CRU) in Yunnan
Project Leader: Lifang Hong, Yunnan Academy of Agrocultural Sciences Soil and Fertilizer Institute, Kunming,
Yunnan. E-mail: gredbean@163.com
Project Cooperator: Mei Yong
The majority of field controlled-release urea (CRU) experiments conducted on maize in recent years were
arranged in north China where 80% of maize in China is grown. In 2011, a field experiment was carried out
in Yunnan, a big maize producer in south China, to investigate performance of CRU in a high fertility sloping
land soil under plastic mulch in humid climate with irregular drought spells in summer. The experiment
included four N rates (0, 105, 157.5, and 210 kg N/ha) replicated three times. Each rate of N was tested as
paired CRU and regular urea (RU) treatments for strict comparison of CRU effect. Two split N treatments
were also included, one with 40% RU basal at seeding and 60% as a top-dressing 53 days after seeding,
compared with 40% RU and 60% CRU both applied basal at seeding. All treatments received equal rates of P
and K fertilizers that were used as basal application.
Results indicated that all the CRU treatments produced higher maize yields compared to its counterpart RU
treatments. The yield increase, however, was not statistically significant, except the CRU versus RU at the full
N rate (210 kg N/ha). Maize yields were increased with an increase in N rates and leveled off at 157.5 kg N/
IPNI Interpretive Summaries 65