18 Dec 2008

Balanced Fertilization on Cash Crops in Southwest China

Balanced fertilization on production of high-yield Baxi banana

Application technologies of K, Mg and S for the first and second Baxi banana plant were studied. The vegetative growth, floral emergence, fruit’s agronomic characteristics, fruit yield and plantation efficiency of different fertilizer combinations including K, Mg and S were compared. Proper use rates of N and K were recommended for two generation Baxi banana, and it was pointed out that if soil was rich in Mg and the ratio of Mg/K was even low to 1.37, Mg was not necessary to be used in banana’s production.

  • Proper ratio of N and K fertilizations on banana production
Research using different rate of N and K fertilizers was conducted to explore proper ratio of N and K fertilization for banana production. The results showed when N and K fertilizers applied at the ratio of N:K2O 1:1.5 highest yield and economic return achieved, and better agronomic characteristic and quality of banana obtained ; but yield decreased when overdosing K; when
N:K2O increased to 1:1.7, agronomic characteristic and quality of banana decreased.

Spatial variability and required proper sample numbers of soil nutrients in banana orchard

156 samples were collected by grid sampling in banana orchard. Spatial variability of soil nutrients was studied according to semivariance analysis by GS+ software, and proper sample numbers of soil nutrients were calculated. It was pointed out that as 54 samples need to be gathered in 100-hectare studied area to meet the demand for scientific fertilization in banana by soil test.

  • Effect of precision nutrient management on NPK use efficiency, yield and quality of flue-cured tobacco
Research on precision NPK management in flue-cured tobacco planted soil was conducted by field experiment in a nutrient monitored village in Qujing. Results showed that on the basis of NPK treatment, missing anyone of the elements could decrease the use efficiency of the others. N use efficiency (NUE) was increased within the range of fertilizer rates as 0 kg/ha~135 kg/ha for N, or 0 kg/ha~240 kg/ha for P or 0 kg/ha~300 kg/ha for K. As the N, P and K application rates were beyond the range, the NUE decreased. Compared to N and K, P use efficiency (PUE) for flue-cured tobacco was quite low. However, PUE was 4.89% higher when 135kg N/ha, 150kg P2O5/ha and 240 kg K2O/ha were applied. Flue-cured tobacco required much higher K than any other nutrients. The highest KUE was measured as 35.76 % for the treatment with 135 kg N/ha, 195 kg P2O5/ha and 240 kg K2O/ha.

Yield and quality of flue-cured tobacco was very responsive to quantity and ratio of NPK fertilizers applied. Missing or overdosing N fertilizer tended to decrease tobacco yield, total sugar and protein but increase alkaloid, and finally lead to imbalanced nutrition and sugar to alkaloid ratio in the tobacco. Missing P or K could cause nutrient imbalance and thus, applied P and K increased sugar content with lower contents of alkaloid and protein.

As NPK use efficiency, flue-cured tobacco quality and economical benefit into account are concerned, application with 135 kg N/ha, 195 kg P2O5/ha and 240 kg K2O/ha is considered as the fertilizer recommendation for flue-cured tobacco in Qujing area.
  • Phosphate and potash significantly improved watermelon yield, sugar content and farmers' income

Research and demonstration trials have been conducted on watermelon for two years in the poverty alleviation project area – Tongxin County. The objectives are to raise watermelon yields and farmers’ income through balanced fertilizer technology. Soil testing revealed that N, P and K are major soil nutrient limiting factors in the region. Fertilizer trial was conducted accordingly. The results of the fertilizer trial were given in Table 1.

Table 1. Effect of different fertilizer treatments on watermelon yields and farmers’ income

*KCl 1650RMB/t, urea:1300RMB/t, super single phosphate:300RMB/t , watermelon:0.5RMB/kg

Results showed that watermelon yields significantly increased with addition of P and K. The optimal K rate was 150 kg/ha on this soil type, above or below which the yield decreased. Application of P had a more pronounced effect on melon yield than K. The optimal treatment increased sugar content of the melon by 2.5% compared to farmers' practice. The effects of P and K on farmers’ economic income showed the same pattern as the yield responses.

Use of balanced fertilizer technology apprears to be a quick and efficient approach to increasing farmers’ income. This approach has been extended to a large area in the county with the local government’s strong support.
  • Nutritional characteristics and K and Mg fertilizer combination in Baxi banana
K and Mg fertilizer combination is important in banana’s production, hence, the nutritional characteristics of Baxi banana (the most popular variety in China) and effect of K and Mg fertilizer combination on its growth were researched. The results of field trial showed that pseudostem and leaf are major parts to accumulate nutrients; the leafy Mg/K ratio fluctuates most greatly during Baxi banana’s growth period; to obtain high yield of 60 metric tones per hectare, 275.3 kg N, 24.6 kg P, 900.0 kg K, 151.2 kg Ca, 73.2 kg Mg, 24.0 kg S, 2091.7 g Fe, 2910.6 g Mn, 228.6 g B and 435.6 g Zn is to be absorbed by the plant. As soil is rich in Mg and Mg/K ratio reaches to 6.87, while great deal of K is applied, Mg addition doesn’t have obvious influence on banana’s foliar nutrition, plant growth, fruit’s agronomic characteristics, fruit quality and yield as well. So, Mg fertilizer is not necessary to be used.
  • Balanced Fertilizers improved Orange Yield and Quality

As invited by the Zizhong Citrus Association, our collaborators from Soil and Fertilizer Institute, Sichuan Academy of Agricultural Sciences conducted an on-site training course of balanced fertilization for citrus farmers. The event was organized by the Zizhong Citrus Association. More than 50 citrus growers were turned out. The courses covered the citrus nutrition, identification of nutrient deficiency symptoms, deficiency correction and high yield and quality orchard management, etc. In the citrus orchard, growers learnt how to differentiate different nutrient deficiency symptoms, saw the effect of balanced fertilization on orange yield, tasted the difference of the orange receiving different fertilizer treatments, and deeply impressed by the effect of balanced fertilization on orange production. The whole story was covered and broadcast by the Neijiang City TV.

The orange was not harvested on the day of training course conducted and thus, there was no yield data available. However, orange quality was analyzed before the training. It showed that the vitamin C in the fruit was increased by 5 mg/100g, sugar content by 8%, and smoothness of the fruit skin by 10%.

Figure 1 Farmers are concentrated on the field lecture Figure 2 The citrus trees receiving BF bore more fruits

  • Potash Significantly Increased Vegetable Yields

Vegetable production increased dramatically in southwest China in recent years because of higher economic return and the government's promotion and incentives as part of reducing production of low quality grain in their new crop program. This has stimulated farmers' interest in using more input for higher yields and profit. Most farmers have tried to achieve this goal by applying large doses of N and P fertilizers but using little or no K to their vegetable crops. According to soil analyses, this fertilizer practice has led to build-up of N and P but depletion of K in these soils. Preliminary work conducted over the last two years shows that a balanced use of NPK fertilizer significantly increased yields of lettuce by 3,787 kg/ha (21.4%), cabbage by 12,925kg/ha (27.7%), garlic bulbs by 709 kg/ha (19.0%), eggplant by 1,750 kg/ha (28.2%), and sweet pepper yields by 5,474-11,701 kg/ha (33.1%-71.3%) in Sichuan and Chongqing. This can be applied to a total of 617 thousand ha of vegetable fields on the Chengdu Plain and in Chongqing. The estimated need for increased K2O use per year on vegetables will reach about 26 thousand tons.

Potassium deficiency symptoms on cauliflower are shown below: K deficiency symptom at early stage on the left and at mature stage on the right.

  • Effect of balanced fertilization on yield and quality of fruit vegetables grown on three acidic soils

Cowpea and pimiento, sweet chilly pepper, are the common fruit vegetables grown in the Chongqing suburbs. However, due to intensified acidification of the vegetable soils, it has made pests and diseases in rampancy and consequently reduced vegetable quality and farmers’ income. The objective of this study was to explore the optimal fertilizer recommendations for production of cowpea and pimiento in Chongqing by using the systematic approaches through field experiments and demonstrations. It was found that balanced fertilization increased the yield of pimiento by 5.4%-66.4% and cowpea by 8.6%-33.6% on three acidic soils. On the basis of this study, optimal fertilizer recommendations were put forward accordingly.

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