Effects of Nitrogen Nutrition on Grain Quality in Upland Rice Zhonghan 3 and Paddy Rice Yangjing 9538 Under Different Cultivation Methods

ACTA AGRONOMICA SINICA Volume 35, Issue 10, October 2009 Online English edition of the Chinese language journal Cite this article as: Acta Agron Sin, 2009, 35(10): 1866–1874.

RESEARCH PAPER

Effects of Nitrogen Nutrition on Grain Quality in Upland Rice Zhonghan 3 and Paddy Rice Yangjing 9538 Under Different Cultivation Methods ZHANG Ya-Jie, CHEN Ying-Ying, YAN Guo-Jun, DU Bin, ZHOU Yu-Ran, and YANG Jian-Chang* Key Laboratory of Crop Genetics and Physiology, Jiangsu Province, Yangzhou University, Yangzhou 225009, China

Abstract: For evaluating the differences between upland and paddy rice (Oryza sativa L.) as well as interaction between cultivation methods and nitrogen (N) levels, the upland rice cultivar Zhonghan 3 (japonica) and the paddy rice cultivar Yangjing 9538 (japonica) were planted in moist cultivation (MC) and bare dry-cultivation (DC). Each cultivar had 3 N-application treatments (100 kgí1 for low N, 200 kgí1 for normal N, and 300 kgí1 for high N) in MC and DC conditions. Compared with normal N treatment, HN reduced grain yield for both cultivars under DC and for the paddy rice cultivar under MC; whereas, it promoted the yield of upland rice under MC. With the increase of N application rate, the percentage of chalky grain and the chalkiness of upland rice increased under DC, however, the 2 indices were the largest in the normal N treatment and the smallest in the high N treatment under MC; for paddy rice, the percentage of chalky grains and the chalkiness showed a declined trend under DC but an in increased trend under MC. Under both MC and DC, the protein content enhanced in both upland and paddy rice when more N was applied, whereas the amylose content declined. The highest breakdown viscosity and the lowest setback viscosity were observed in upland rice treated with normal N and in paddy rice treated with low N. Compared with MC, DC improved the appearance quality and the nutrient quality of upland rice, and there was no significant variations in other quality indices between upland and paddy rice. The upland rice had better nutrient quality but poorer appearance and cooking qualities than paddy rice. The cooking and nutrient qualities showed lower correlations to the leaf N content in upland rice than paddy rice. These results suggest that the response of upland rice to cultivation method and N level is in great difference to that of paddy rice. Keywords: upland rice; paddy rice; dry cultivation; nitrogen; rice quality

To meet the challenge of drought in China, water-saving techniques have been developed and applied in rice (Oryza sativa L.) growing areas since the last decade in the 20th century, for example, dry-cultivation technique for paddy rice and acreages of upland rice in rainfed areas. Upland rice is a rice variant that can be grown in arid eco-environment without irrigation in the whole growth period. It possesses high resistances to drought and barren soil, and can save 70% of irrigation water compared to paddy rice. The interaction between nitrogen (N) and water supply under drought stress becomes one of the research priorities in nutritional physiology [1, 2]. There are many studies focused on rice quality under different N application levels, and most investigators believe that N supplement may increase protein

content and decrease amylose content [3–23]. With regard to rice grain quality, some experiments showed that the percentage of chalky grain and the chalkiness were reduced when more N fertilizer was applied [3–5]. However, reverse results were also reported [5–10]. Besides, reduced breakdown viscosity [14] and increased setback viscosity [15] were also reported in accompany with enhanced nitrogen application. The effect of cultivation method on rice grain quality was inconsistent in different experiments [24–31]. In some reports, dry cultivation resulted in the reduced percentage of chalky grains [28–30] and increased gel consistency and setback viscosity [29, 30]. However, Yang et al. [31] showed that dry cultivation decreased gel consistency and increased gelatinization temperature of rice grains; whereas, chalkiness

Received: 5 January 2009; Accepted: 15 April 2009. * Corresponding author. E-mail: [email protected] Copyright © 2009, Crop Science Society of China and Institute of Crop Sciences, Chinese Academy of Agricultural Sciences. Published by Elsevier BV. All rights reserved. Chinese edition available online at http://www.chinacrops.org/zwxb/ DOI: 10.1016/S1875-2780(08)60112-1

ZHANG Ya-Jie et al. / Acta Agronomica Sinica, 2009, 35(10): 1866–1874

varied among cultivars, and no significant difference in amylose content was observed. There are few studies on grain quality influenced by N nutrient in combination with cultivation method, and the conclusions are inconsistent [16–23]. For example, in some experiments, water-saving irrigation significantly reduced the crude protein content of rice grains and improved the chalkiness and amylose content [16, 17] under the same N level. Under the same irrigation, N supplement significantly promoted the protein content, chalky percentage, and chalkiness degree but reduced the amylose content [17]. In another experiment using hybrid rice, no significant variation of amylose content was caused by irrigation and fertilization treatments, but the protein content varied significantly [18]. Thus, we carried out experiments in this topic under moist cultivation and bare dry-cultivation with 3 N levels to provide theoretical and practical guidance to rice production that aimed at saving water, minimizing fertilizer application, high-yielding, and good quality.

1 1.1

Materials and methods Materials and experimental conditions

The upland rice cultivar Zhonghan 3 (japonica) and paddy rice cultivar Yangjing 9538 (japonica) were grown in the farm of Yangzhou University, Yangzhou, China after harvesting wheat (Triticum aestivum L.). The sandy soils contained basic nutrients as follows: organic matter of 2.05%, available N of 107.6 mg kg1, available phosphorus of 26.1 mg kg1, and available potassium of 95.4 mg kg1. The precipitation was 645.7 mm during the rice growth period from June to September. 1.2

Experimental design

The 2 cultivation methods were moist cultivation (MC, control) and barely dry cultivation (DC). The MC followed the conventional irrigation for rice high-yielding production, that is, keeping a water layer in the field from transplanting to regreening, alternating wet and dry soils during the other growth periods, and stopping water supply 1 week before harvest. The total quantity of irrigation was 5600 m3 ha1. In the DC treatment, the field was dry-plowed before making beds. The beds were fully watered from transplanting to 1 week after transplantation when plants were alive. Water was only supplied at vigorous tillering, booting, and heading stages with a total amount of 920 m3 ha1. From heading to maturity, the soil moisture was monitored by tensiometers (Nanjing Institute of Soil Science of the Chinese Academy of Sciences, Nanjing, China) that were installed in the field. The soil water potential ranged normally from 15 to 25 kPa, except for the obvious influence (0 to 10 kPa) after 3 rainfalls at grain filling stage (10–12, 26–28, and 38–42 d after heading) in DC plot. Low, normal, and high N levels

corresponding to N rate at 100 (LN), 200(NN), and 300 (HN) kg ha1, respectively, were applied at a ratio of 50% for basal fertilizer, 20% for tillering fertilizer, and 30% for panicle fertilizer. Calcium superphosphate and potassium chloride were applied at 750 and 300 kg ha1 before transplanting. Boundary ridges between plots (1 m in width) were separated by plastic film. The experiment was a blocked split–split–plot design, in which cultivation method was the main plot, and N level and cultivar were the split–plot and split–split plot (plot), respectively. The plot area was 1.5 × 6 m with 3 replicates. Seeds were sown on May 14, and the seedlings (dry-raised) were transplanted on June 16. The hill space was 10 × 25 cm with 2 seedlings per hill. 1.3

Plant sampling and measurements

1.3.1 Yield Fifty hills of rice plants were harvested from each plot to record grain yield at maturity. 1.3.2 Determination of main quality indicators Grains harvested were flowed by an air classifier (NP4350, USA). Percentage of chalky grains, chalkiness degree, ratio of grain length-to-width, amylose content, and the crude protein content were determined with reference to the national standards for high-quality rice (GB/T/7891-1999). Amylose content was determined by the rapid near-infrared grain quality analyzer (Foss TECATOR, Sweden). 1.3.3 Viscosity of rice starch Starch viscosity characteristics were determined with Super 3-type of Rapid Viscosity Analyzer (RVA, Newport, Australia), and analyzed with thermal cycle for Windows (TWC) software. In accordance with the American Association of Cereal Chemists (AACC) method (1995-61-02) and the standard method suggested by the Royal Australian Chemical Institute (RACI), when water content of rice was 12.00%, the sample was 3.0000 g and the distilled water was 25.0000 g. During mixing, the temperature in tank rose from 50qC (maintaining 1 min) to 95qC in 3.8 min at a rate of 11.84qC min1 (maintaining 2.5 min), and cooled down to 50qC at the same rate. Finally, the temperature was maintained for 1.4 min. The stirrer rotation speed was 960 r min1 at the initial 10 s, and turned to 160 r min1 afterwards. The RVA viscosity in centi-Poise (cP) was characterized with the parameters of peak viscosity, hot viscosity, final viscosity, breakdown viscosity, and setback viscosity. 1.3.4 Number of roots Rice roots were excavated from soil in approximate volume of 10 × 8.5 × 20 cm. The roots were carefully rinsed and detached from their nodal bases. Three hills were sampled from each plot at heading stages. The number of adventitious roots was counted. 1.3.5 Determination of N content in leaves Plants of 5 hills sampled from each plot at jointing, heading, and maturity stage were separated into living and dead leaf tissues, stem (including leaf sheath), and panicle (when available). All the

ZHANG Ya-Jie et al. / Acta Agronomica Sinica, 2009, 35(10): 1866–1874

plant samples were oven-dried at 80°C for 72 h. After milled through 0.5 mm mesh, the leave samples were ready for determining N concentration using a micro-Kjeldahl procedure. 1.4

Statistical analysis

Data were arranged with the Microsoft Excel 2000 software and statistically analyzed using SPSS10.0 package. The graphs were generated using SigmaPlot 8.02.

2

Results

2.1 Effects of N nutrition on grain yield of upland and paddy rice under MC and DC Under DC, Zhonghan 3 had the highest yield in NN treatment, which was higher than that in LN treatment by 81.7%. However, the yield difference between NN and HN treatment was not significant. A similar pattern of yield response to N supply was observed in Yangjing 9538, but the yield increases, compared to LN treatment, were 28.0% and 29.2% in HN and NN treatment, respectively. Under MC, Zhonghan 3 had the highest yield in HN treatment. Compared to LN, HN and NN treatment had a higher yield by 85.2% and 68.6%, respectively. The yield difference of Zhonghan 3 was significant between HN and NN treatment. For Yangjing 9538, the highest yield was observed in NN treatment, and the HN and NN treatments increased yield by 29.7% and 45.4%, respectively. However, the yield in HN treatment was significantly lower than that in NN treatment (Fig. 1). These results showed that the interaction between soil moisture and N fertilizer had a remarkable influence on rice yield in both paddy and upland rice. The average yield of Zhonghan 3 under DC was lower than that under MC by 7.7%. Similarly, the yield reduction of Yangjing 9538 under DC was 12.3%. Under MC, grain weight

of Zhonghan 3 increased when more N was applied. Overall, Yangjing 9538 had the highest yield in NN treatment. The average yield of paddy rice was higher than upland rice by 13.9%. The results indicated that the responses of yield to cultivation methods and N fertilizer treatments were different between upland rice and paddy rice. Under DC, the increases of yield and N utilization efficiency were not distinct in both upland and paddy rice in HN treatment. Under MC, upland rice still showed a high yield potential, even under HN condition; whereas, paddy rice had the opposite performance. Under DC, yield reductions were observed in both upland and paddy rice, particularly in paddy rice. 2.2 Effects of N nutrition on grain quality in upland and paddy rice under MC and DC 2.2.1 Appearance of quality Under DC, Zhonghan 3 had the highest percentage of chalky grains and chalkiness degree in NN treatment. The chalky percentage in NN treatment was not significantly different to that in HN treatment, but the difference of chalkiness degree was significant. The ratio of grain length-to-width was the largest in the LN treatment. The percentage of chalky grains and chalkiness degree in Yangjing 9538 decreased under HN and NN conditions in contrast to those at LN condition. There was no significant difference between HN and NN. The ratio of grain length-to-width had a growing trend in HN and NN treatments than that in LN, but the discrepancies were not significant (Table 1). Under MC, the percentage of chalky grains and the chalkiness degree of Zhonghan 3 were the highest in NN treatment with significant differences to LN and HN treatments. The ratio of grain length-to-width was the largest in HN treatment with a significant increment to that in LN treatment. Compared with the LN treatment, HN and NN treatments reduced the percentage of chalky grains and chalkiness degree of Yangjing

10 Zhonghan 3

Yangjing 9538

Grain yield (t ha1)

8 6 4 2 0 DC

MC

DC

MC

Cultivation method LN

Fig. 1

NN

HN

Effect of N nutrition on grain yield of upland and paddy rice under dry cultivation (DC) and moist cultivation. (MC) LN: Low nitrogen (100 kg ha1); NN: Normal nitrogen (200 kg ha1); HN: High nitrogen (300 kg ha1).

ZHANG Ya-Jie et al. / Acta Agronomica Sinica, 2009, 35(10): 1866–1874

Table 1 Effect of N nutrition on grain yield in upland and paddy rice under DC and MC Cultivation method

Percentage of

Chalkiness

Ratio of grain

chalky grains (%)

degree (%)

length-to-width

LN

23.1 cd

12.4 c

2.93 a

NN

25.8 b

16.2 b

2.86 ab

HN

25.5 b

12.7 c

2.87 ab

Average

24.8 NS

13.8 NS

2.89 NS

25.3 bc

12.9 c

2.77 b

NN

28.5 a

19.1 a

2.77 b

N level

Zhonghan 3 DC

MC (Control) LN HN

22.8 d

12.4 c

2.94 a

Average

25.5

14.8

2.83

LN

22.0 a

13.8 a

1.69 b

NN

19.3 bc

10.6 b

1.77 ab

HN

17.8 cd

10.0 b

1.82 a

Average

19.7 NS

11.3 NS

1.76*

15.8 d

8.5 c

1.67 b

NN

19.0 bc

10.9 b

1.69 b

HN

21.0 ab

12.0 ab

1.68 b

Average

18.6

10.5

1.68

Yangjing 9538 DC

MC (Control) LN

In each cultivar, values followed by different letters denote significant difference among N treatments at P < 0.05. The means are compared between MC and DC; an asterisk stands for significant difference at P < 0.05 and “NS” for non significant difference. DC: Dry cultivation; MC: Moist cultivation. LN: Low nitrogen (100 kg ha1); NN: Normal nitrogen (200 kg ha1); HN: High nitrogen (300 kg ha1).

9538. There were no significant differences in the ratio of grain length-to-width in 3 N levels (Table 1). In Zhonghan 3, slightly lower percentage of chalky grains and chalkiness degree of Zhonghan 3 were observed under DC than under MC, and the ratio of grain length-to-width was larger under DC than under MC; but there was no significant difference between DC and MC. In Yangjing 9538, the percentage of chalky grains and the chalkiness degree were slightly higher under DC than those under MC, but the ratio of grain length-to-width was significantly larger under DC. Compared with Yangjing 9538, Zhonghan 3 had higher percentage of chalky grains, chalkiness degree, and ratio of grain length-to-width by 31.4, 30.2, and 66.1%, respectively (Table 1). These results indicated that N supplement from the LN to NN under both DC and MC resulted in enhanced percentage of chalky grains and chalkiness degree in Zhonghan 3, but the 2 indices declined when the N nutrient reach the high level. With the increase of N level, the percentage of chalky grains and chalkiness degree in Yangjing 9538 declined under DC, but increased under MC. DC improved the appearance of quality in upland rice and slightly degraded that in paddy rice.

In generally, upland rice presented a worse appearance of quality than paddy rice. 2.2.2 Cooking and nutritional quality Under DC, the amylose content decreased significantly in Zhonghan 3 treated with NN and HN compared with LN, and the protein content significantly increased. The amylose content was not significantly different between NN and LN treatments, but the protein content was reverse. The amylose content and protein content were similar in Yangjing 9538. Under MC, Zhonghan 3 had significantly lower amylose content in HN treatment than that in LN treatment, and had no significant difference between NN and LN treatments. The protein content was not significantly different between NN and HN treatments, but both higher than that in LN treatment. In Yangjing 9538, similar results were observed (Table 2). In comparison with MC, DC resulted in increased amylose content and protein content in Zhonghan 3 and no significant variations in Yangjing 9538 showed no significant difference in amylose content and protein content. The amylose content and protein content in Zhonghan 3 were higher than those of Yangjing 9538 by 23.6 % and 5.0%, respectively. The average yield of Yangjing 9538 was higher than that of Zhonghan 3 by 13.9% (Table 2). These results showed the positive effect of N supplement on protein content but negative effect on amylose content under both MC and DC. The nutrition quality of upland rice was improved under DC, but the effect on cooking quality was not significant. However, DC had no significant effect on cooking and nutritional quality in paddy rice. Upland rice was better in the nutritional quality, but inferior to cooking quality than paddy rice. 2.2.3 RVA profile parameters Under DC, Zhonghan 3 had the highest peak viscosity and breakdown viscosity, and the lowest final viscosity and setback viscosity. However, there was no significant difference among treatments. With the increase of N level, Zhonghan 3 showed declined hot viscosity and higher gelatinization temperature, whereas Yangjing 9538 had declined peak viscosity, hot viscosity, breakdown viscosity, and final viscosity and higher setback viscosity and gelatinization temperature. However, the differences of breakdown viscosity and setback viscosity were not significant between NN and HN. Similar patterns of the RVA profile parameters were observed in Yangjing 9538 under both conditions of MC and DC (Table 2). In Zhonghan 3, the average peak viscosity and hot viscosity were higher under DC than those under MC, but the breakdown viscosity, final viscosity, setback viscosity, and gelatinization temperature were lower under DC. Significant differences were observed in final viscosity and setback viscosity. In Yangjing 9538, these parameters were lower under DC than those under MC, of which the difference in final viscosity was significant. Compared with Yangjing 9538, Zhonghan 3 presented higher peak viscosity, breakdown

ZHANG Ya-Jie et al. / Acta Agronomica Sinica, 2009, 35(10): 1866–1874

Table 2 Effects of N nutrition on cooking and nutrition qualities and RVA profile parameters of rice under DC and MC Cultivation method N level

Amylose content (%) Protein content (%)

PKV (cP)

HTV (cP)

BDV (cP)

FNV (cP)

SBV (cP)

PT (qC)

Zhonghan 3 DC

LN

20.92 a

6.93 d

3001 a

1478 a

1523 a

2822 b

179 b

80.7 a



NN

18.78 b

7.74 bc

3049 a

1474 a

1575 a

2783 b

266 b

81.5 a



HN

18.53 ab

8.85 a

2952 a

1419 ab

1534 a

2794 b

159 b

81.5 a



Average

19.41 NS

7.84*

3001 NS

1457 NS

1544 NS

2800*

201*

81.1 NS

MC (Control)

LN

19.96 ab

6.57 d

3082 a

1427 a

1655 a

3004 a

78 b

80.9 a



NN

19.63 ab

7.44 c

3158 a

1481 a

1678 a

2822 b

336 b

81.3 a



HN

16.12 c

8.06 b

2647 b

1313 b

1334 b

3081 a

434 a

81.7 a



Average

18.57

7.36

2962

1407

1555

2969

7

81.3

Yangjing 9538 DC

LN

16.08 a

6.57 c

3066 ab

1582 ab

1484 ab

2691 ab

374 bc

75.2 b

NN

15.31 ab

7.35 b

2861 bc

1420 c

1442 abc

2510 c

351 bc

76.0 b

HN

14.46 bc

7.94 a

2583 d

1236 d

1310 c

2361 d

230 ab

86.1 a

Average

15.29 NS

7.29 NS

2837 NS

1412 NS

1412 NS

2521*

318 NS

79.1 NS

LN

16.19 a

6.64 c

3195 a

1623 a

1572 a

2779 a

417 c

74.8 b



NN

15.87 a

7.35 b

2870 bc

1452 bc

1418 bc

2595 bc

275 abc

76.0 b



HN

14.16 c

7.59 b

2655 cd

1360 cd

1295 c

2505 c

150 a

85.9 a



Average

15.41

7.19

2907

1478

1428

2626

280

78.9

MC (Control)

In each cultivar, values followed by different letters denote significant difference among N treatments at P < 0.05. The means are compared between MC and DC; an asterisk stands for significant difference at P < 0.05 and “NS” for non significant difference. DC: Dry cultivation; MC: Moist cultivation. LN: Low nitrogen (100 kg ha1); NN: Normal nitrogen (200 kg ha1); HN: High nitrogen (300 kg ha1).

viscosity, and hot viscosity with no significant differences, and significant lower (67%) setback viscosity (Table 2). Under both DC and MC conditions, the highest breakdown viscosity and the lowest setback viscosity appeared in NN treatment for upland rice and in LN treatment in paddy rice. With the increase of N level, breakdown viscosity and setback viscosity were reduced. This indicated that the cooked rice tended to softness and stickiness in upland rice treated with NN; whereas, such a change was observed in cooked rice of paddy rice treated with LN. Further supplements with N fertilizer would degrade cooking quality, and upland rice had stronger tolerance of rice taste and texture to N than paddy rice. 2.3 Effects of N nutrition on adventitious root number of upland and paddy rice under MC and DC Under DC, the increment of N nutrition resulted in more adventitious root at heading stage in Zhonghan 3 and Yangjing 9538. Under MC, the dynamic trend of adventitious root number was similar in both cultivars (Fig. 2). Compared to MC, DC reduced the average number of adventitious root of Zhonghan 3 and Yangjing 9538 at heading stage by 30.3% and 12.3%, respectively. The adventitious root number was 56.5% lower in Zhonghan 3 than in Yangjing 9538. The results indicated that the adventitious root number of upland and paddy rice increased when more N was applied. The adventitious root number was smaller under DC than MC for

both paddy and upland rice. Compared to upland rice, paddy rice had more adventitious roots approximately 2.3 folders. 2.4

Correlations of leaf N content with grain quality

In both cultivars, the grain protein content and setback viscosity were positively correlated with leaf N content at jointing, heading, and maturity and the change of leaf N content from heading to maturity with the correlation coefficient ranging from 0.7921 (P < 0.05) to 0.9875 (P < 0.01) and 0.1611 (P > 0.05) to 0.9850 (P < 0.01), respectively. However, amylase content and breakdown viscosity were negatively correlated with leaf N content with the coefficient ranging from 0.5670 (P > 0.05) to 0.9225 (P < 0.01) and 0.3947 to 0.9629 (P < 0.01), respectively. The leaf N content of Zhonghan 3 showed weaker correlations with protein content, amylose content, breakdown viscosity, and setback viscosity at jointing, heading, and maturity stage as compared with Yangjing 9538, and the decline of leaf N content from heading to maturity was also weakly correlated with the above quality parameters in Zhonghan 3 (Table 3). This indicated that cooking and nutrition qualities responding to N nutrition in a lower degree in upland rice than paddy rice.

3

Discussion

Although the effects of N nutrition on quality traits and parameters of rice grain were inconsistent in different experiments,

ZHANG Ya-Jie et al. / Acta Agronomica Sinica, 2009, 35(10): 1866–1874

Root number per hill

400

Zhonghan 3

Yangjing 9538

300

200

100

0

DC

DC

MC

MC

Cultivation method LN

Fig. 2

NN

HN

Effect of N nutrition on adventitious root number of upland and paddy rice under different cultivation methods DC: Dry cultivation; MC: Moist cultivation. LN: Low nitrogen (100 kg ha1); NN: Normal nitrogen (200 kg ha1); HN: High nitrogen (300 kg ha1).

Table 3 Correlation coefficients of leaf N content with quality parameters of grain (n = 6) Growth stage

Zhonghan 3 Protein content

Jointing

0.9807**

Amylose content 0.5670

Yangjing 9538 BDV

SBV

Protein content

Amylose content

BDV

SBV

0.3947

0.1611

0.7921*

0.8358**

0.9029**

0.9850**

Heading

0.9380**

0.7853*

0.5639

0.4072

0.9875**

0.9192**

0.9179**

0.8308*

Maturity

0.8614**

0.6230

0.5279

0.3278

0.9566**

0.9225**

0.9629**

0.8633**

From heading to maturity

0.8789**

0.8377**

0.5179

0.4294

0.9848**

0.8927**

0.8606**

0.7851*

* P < 0.05; * P < 0.01.

it is generally accepted that there is a positive effect of N nutrition on grain protein content and a negative effect on amylose content [3–23]. Sun et al. [14] and Ye et al. [15] reported that the maximum viscosity and breakdown viscosity reduced accompanying with the increase of N application, but the setback viscosity had an increment. In this study, the highest breakdown viscosity and the lowest setback viscosity were observed in upland rice treated with NN and in paddy rice treated with LN. When more N fertilizer was supplemented, the breakdown viscosity was reduced and the setback viscosity was increased, leading to worse cooking and tasting qualities, because larger breakdown viscosity was responsible for soft texture of rice, a negative setback viscosity for sticky rice, and a positive setback viscosity for hard and rough rice [32]. The upland cultivar tended to be in soft and sticky quality in the NN treatment, but the paddy rice cultivar had similar change in the LN treatment. This indicates that upland rice possesses a higher tolerance to N nutrition than paddy rice in terms of taste and texture of rice. Compared with paddy rice, the leaf N content of upland rice had weaker correlation with protein content, amylose content, breakdown viscosity, and setback viscosity at jointing, heading, and maturity stages, indicating an insensitive response to N uptake of upland rice. The reasons are possibly in 2 aspects. First, upland rice has less

adventitious roots per hill (approximate 0.43 folder of paddy rice at heading stage), resulting in relatively weak ability of N uptake. Second, compared with paddy rice, upland rice has a series of characteristics in favor of stems growth and grain filling, such as faster decline of Soil and Plant Analyzer Development (SPAD) value and N content in flag leaves after anthesis, lower relative N content, lighter leaf color, larger C/N ratio, and relatively larger quantity of carbohydrate accumulation [33, 34]. The effect of soil moisture on grain quality of rice varies in different experiments [24–31]. Guo et al. [28], Li et al. [29], and our earlier study [30] found that the percentage of chalky grains decreased under DC. Besides, Guo et al. [28] also reported different amylase content of upland and paddy rice between water-sowing and dry-sowing cultivations; both gel consistency and setback viscosity were promoted. However, Yang et al. [31] revealed that the percentage of chalky grains under DC increased in japonica rice but decreased in indica rice; chalkiness varied in different cultivars. DC decreased gel consistency of grain and increased gelatinization temperature. We also observed different response of grain quality of upland and paddy rice to cultivation method in this study. For example, Zhonghan 3 has lower percentage of chalky grains and chalkiness, higher protein content, and better appearance

ZHANG Ya-Jie et al. / Acta Agronomica Sinica, 2009, 35(10): 1866–1874

and nutrient qualities under DC than under MC. This result is consistent with our earlier report [30]. Yangjing 9538 has slightly higher percentage of chalky grains and chalkiness, higher protein content, no significant changes of other quality parameters under DC than under MC. This is not consistent with the findings in other experiments, and the discrepancy might be related to variety, cultivation environment, and the soil moisture at filling stage. In studies with the combination of cultivation method (soil moisture) and N nutrition, Chen et al. [16] and You et al. [17] showed significantly reduced milled rice percentage, crude protein content, and gel consistency and improved chalkiness and amylose content in scanty irrigation treatments with same N level. Under the same irrigation condition, the milled rice percentage, crude protein content, percentage of chalky grains, chalkiness, and gel consistency increased when the N level was promoted, and the amylose content was reduced simultaneously [17]. In an opposite view, Cheng et al. [18] pointed out that there was significant effect of irrigation and fertilization on protein content in early-season of hybrid rice, and the amylase content was slightly influenced. The effect of cultivation method by N nutrition on grain quality of upland has not been reported yet. In this study, under both DC and MC, the upland rice cultivar presented a reduction of amylose content and an increment of protein content with raising N level, which was similar to the paddy rice cultivar. In contrast, the percentage of chalky grains and the chalkiness were in different variations between upland and paddy rice under the 3 N levels. In the upland rice cultivar, the highest percentage of chalky grains and chalkiness appeared in the NN treatment under both DC and MC; however, the paddy rice cultivar had the largest values in LN treatment under DC and in HN treatment under MC. The inconsistent results and conclusions across different experiments might be owing to the variety speciality of quality in response to N nutrition and the complex growing environments, such as temperature, light, and water conditions. In particular, a rice variety has its optimal N requirement during the growing period, and the excessively low or high N input will increase the chalkiness of grain. Completely different performances of grain yield were observed in upland and paddy rice growing in HN by MC condition compared with NN by MC condition, of which upland rice significantly increased yield and paddy rice significantly decreased yield. This implies that the yield of upland rice, similar to grain quality, is less sensitive to N level than that of paddy rice. Therefore, in rice cultivation aiming at high yield and good quality, management measures should be carried out subject to cultivar characteristics. For instance, upland rice cultivars can be supplied with moderately higher N rate than paddy rice cultivars in dry cultivation. In spite of paddy or upland rice cultivars, high yield depends on strong ability of N absorption, utilization, and transportation to

panicles [14]. Although increasing N fertilizer amount and the delayed fertilizing may improve rice nutritional quality, the cooking and tasting quality are degraded. The optimal combination of soil moisture and the application amount and time of N fertilizer need to be studied in details.

4

Conclusions

Under DC, N application over normal level had no contribution to yield promotion in both upland and paddy rice. Under MC, upland rice had the potential of yield increase because it was less sensitive to N application than paddy rice. With the increase of N level, the percentage of chalky grains and chalkiness showed the “up–down” trend in upland rice under DC and MC; whereas, they were continuously reduced in paddy rice under DC and continuously enhanced in paddy rice under MC. Under DC and MC, with the increase of N level, amylose content decreased and protein content increased in both upland and paddy rice. The highest breakdown viscosity and the lowest setback viscosity were observed in upland rice under NN and in paddy rice under LN. Compared with MC, DC improved appearance and nutrient qualities of upland rice, and caused no significant differences in other quality parameters. These quality parameters also had no significant changes in paddy rice between DC and MC conditions. The correlation coefficients between cooking and nutrient qualities and leaf N content were smaller in upland rice than in paddy rice.

Acknowledgments This study was supported by the grants from the National Natural Sciences Foundation (30671225 and 30771274), the Natural Sciences Foundation of Jiangsu Province, China (BK2006069), and the Scientific Starting Fund for Senior Researchers in Yangzhou University, China.

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