Americas and Oceania Group - International Plant Nutrition Institute

Effect of Potassium Rates on Litchi Quality in Guangdong
Project Leader: Dr. Lixian Yao, Guangdong Academy of Agricultural Sciences, Guangzhou, Guangdong.
E-mail: lyaolx@163.net
This 3-year study, initiated in 2009, aimed to investigate the effect of different ratios of K to N on litchi
yield and quality in Guangdong province. There were five K: N ratios employed ranging from 0.6 to 1.2 based
on the fixed N rate of 500 kg N/ha and P rate of 150 kg P 2 O 5 /ha. Appropriate amounts of Ca, Mg, Zn, B, and
Mo fertilizers were added to each treatment as identified by soil test and previous studies. The popular litchi
cultivar, Feizhixiao, was selected for the field experiment. All nutrients were applied four times in the odd
years: after harvest, before blossom, at young fruit setting and fruit expansion, and two times in the even year:
after harvest and between young fruit setting and fruit expansion. The results obtained from this experiment
along with other related studies will be used to develop the best nutrient management for litchi in southern
China.
Results showed that the K: N ratio at 1:1 generally favored all the growth parameters of litchi such as
phonological index, enzyme activity, plant hormones, fruit yield, and quality. The parameters tended to
gradually become unfavorable as the K: N ratio deviated from 1:1. The contents of hydrogen peroxidase
and starch in leaf, indoleacetic acid (IAA) in male flower, and fruit yield were the highest in the treatment
of K: N ratio at 1:1. Further, the fluorescent index of chlorophyll was moderate in late April and the highest
in late November. The percent of flowering trees and flowering branches at blossom, contents of Abscisic
Acid (ABA) and zeatin (ZT) in male flower as well as ZT in female flower were at moderate levels while
ABA contents in female flower were the lowest. Amino acids that are believed to govern fruit palatability
consisting of delicacy, sweetness, and fragrance (mainly from aromatic amino acids) were relatively richer
than the other treatments. The remaining parameters appeared to be similar in all treatments. Since economic
benefit is usually closely correlated to yield and input cost, this treatment resulted in the highest net income of
USD 9,040 in 2010 and USD 10,849 in 2011. This study demonstrates that optimal fertilization is crucial and
effective in improving litchi yield and farmer income. Guangdong-BFDP-09
Effect of Different Fertilizer Treatments on Chili Pepper Production in Hainan
Project Leader: Liangshang Xie, Hainan Academy of Agricultural Sciences Soil and Fertilizer Institute #9, Haikou,
Hainan. E-mail: lsxie@163.com
Project Cooperator: Zhang Wen
The study continued to verify the optimal fertilizer rates tested in 2010 for chili pepper, one of the most
widely grown vegetables during winter on this tropical island, and the results will be used to guide fertilizer
application for local technicians and vegetable growers. The experiment consists of six rates of N (0, 300,
375, 450, 525, 600 kg N/ha), P (0, 60, 120, 180, 240, 300 kg P 2 O 5 /ha) and K (0, 225, 300, 375, 450, 525 kg
K 2 O/ha). The rates were further fine-tuned based on the yield results from the previous field experiments. The
source, timing, and placement of the fertilizers, as well as field management remained the same.
Results showed that the chili pepper yields significantly increased with increased rates of N, P, and K,
but leveled off at 300 kg N/ha and 300 kg K 2 O/ha. Though the rate of 180 kg P 2 O 5 /ha produced the highest
pepper yield, the increment was modest. The result verified that 300 kg N/ha plus 300 kg K 2 O/ha were the
optimal rates for chili pepper in Hainan on acid, sandy soils. This fertilizer combination could produce 65
t/ha of chili pepper and net income of USD 11,391. Furthermore, it also achieved the highest agronomic
efficiency for N (147 kg pepper/kg N) and K (32 kg pepper/kg K 2 O). Based on the two years of experiments,
recommendations for NPK fertilization for chili pepper on the Hainan Island can be 300-60-300 kg N- P 2 O 5 -
K 2 O/ha. If soil testing indicates a high soil P, P fertilizer can be omitted from the fertilizer program every
other crop season or until further study is completed related to P use. Hainan-BFDP-08
Nutrient Losses from Sloping Lands as Affected by Nitrogen Sources and Surface Mulch in Sichuan
Project Leader: Chaowen Lin, Sichuan Academy of Agricultural Sciences Soil and Fertilizer Institute, Chengdu, China.
E-mail: linchaowen2002@yahoo.com.cn
The objective of this project was to further evaluate the effects of different N sources and surface mulching
methods on corn yield and nutrient losses from Sichuan’s sloping farmlands during the summer rainy season.
There were four N sources including ammonium N (ammonium bicarbonate, ABC), nitrate N (calcium
nitrate), amide N (urea), and controlled-release (CRU) urea and three types of surface mulching (no mulch,
wheat straw, and plastic film) employed in the field experiment. The fertilizer rates were 300-150-150 kg
N-P 2 O 5 -K 2 O/ha based on the previous experiments.
64 IPNI Interpretive Summaries