Effects of rice or wheat residue retention on the quality of milled japonica rice in a rice–wheat rotation system in China

In rice–wheat rotation systems, crop straw is usually retained in the field at land preparation in every, or every other, season. We conducted a 3-year-6-season experiment in the middle–lower Yangtze River Valley to compare the grain qualities of rice under straw retained after single or double seasons per year. Four treatments were designed as: both wheat and rice straw retained(WR), only rice straw retained(R), only wheat straw retained(W), and no straw retained(CK). The varieties were Yangmai 16 wheat and Wuyunjing 23 japonica rice. The results showed contrasting effects of W and R on rice quality. Amylopectin content, peak viscosity, cool viscosity, and breakdown viscosity of rice grain were significantly increased in W compared to the CK, whereas gelatinization temperature,setback viscosity, and protein content significantly decreased. In addition, the effect of WR on rice grain quality was similar to that of W, although soil fertility was enhanced in WR due to straw being retained in two cycles. The differences in protein and starch contents among the treatments might result from soil nitrogen supply. These results indicate that wheat straw retained in the field is more important for high rice quality than rice straw return, and straw from both seasons is recommended for positive effects on soil fertility.     

Effects of spermine and spermidine on the germination of rice seeds under different temperatures

Polyamine , including putrescine (Put) , spermidine(Spd), and spermine(Spm) , are a kind of regulating substances known extensively inhigher plants at present. Different results have been reported on the relationship between polyamines and seed germination (wheat, tobacco and potato). This study investigated the effects of spormine and spermidine on germination of rice seeds.     

Rice–wheat cropping system: tillage,mulch, and nitrogen effects on soil carbon sequestration and crop productivity

Maintenance of organic carbon in soil (SOC) is critically important for sustained agricultural productivity and environmental quality. This paper presents SOC resulting from differences in tillage types and demonstrates how mulch and nitrogen (N) application can mediate the tillage functions on SOC and crop productivities. The results are derived from a 4-year field-scale study carried out in a low-land under sub-tropical hot and humid environment of Nepal. It compared eight treatment combinations, viz., tillage (no-tillage and conventional tillage), mulch (no-mulch and 12 Mg ha^?1 year^?1 of mulch), and N application (recommended versus leaf color chart method) under rice–wheat cropping system. Seasonal grain and biomass yields of these crops were recorded and at the end of the 4-year study, quantified the organic carbon stock of soil; Within 15 cm of surface soil, SOC stock (Mg C ha^?1) was statistically (p < 0.05) higher on no-tillage plots (11.2–11.8) than on conventional tillage plots (9.2–10.5). The treatment effect was more pronounced on winter wheat productivity where conventional tillage combined with straw-mulch exceled the performance of no-tillage. Clearly, no-tillage had the environmental benefit, and conventional tillage had the crop productivity benefit.     

Effects of field high temperature on grain yield and quality of a subtropical type japonica rice—Pon-Lai rice

Typical japonica type rice is sensitive to high temperature. Pon-Lai rice is a special japonica type with adaptation to the subtropical climate in Taiwan. Facing climate change, rising temperatures would damage the yield and quality of rice production. This research was conducted using Pon-Lai rice in the field of a subtropical climate. We conducted 2 experiments, including a year-round experiment and collection of samples from different districts for building different temperature conditions. We analyzed the correlation between rising temperature and rice yield or quality. In our results, the critical period of temperature effect is 0–15 days after heading (H15). The threshold of high temperature damage in yield and appearance quality was 25–27 °C. Grain weight decreased about 2–6%, while the temperature of H15 was raised 1 °C above the thresholds. Perfect grain ratio and chalky grain ratio decreased and increased, respectively, while the temperature of H15 was raised above the thresholds. However, the high temperature in H15 affected the physicochemical characteristics. In addition, we found positive correlation between grain length to width ratio and perfect grain ratio. Grain length to width ratio could be an index of temperature effects for grain quality. In our study, when the temperature was below 30 °C, a rising temperature of H15 could damage rice yield and appearance quality, and change grain shape. Our results could provide reference for dealing with the warming future in other temperate rice-cultivated countries.     

Relative abundance and damage of some insect pests of wheat under different tillage practices in rice–wheat cropping in India

Tillage changes the physical and chemical properties of soil and can also inhibit or enhance useful and harmful fauna. In agriculture, different tillage technologies are being tried to enhance crop productivity, but little concrete information seems to exist on their effects on pest abundance and damage. To address this lack of information, sowing of wheat was investigated under different tillage systems. In order to monitor pest abundance and damage in altered tillage systems, the present studies on the relative abundance and damage due to insect pests viz. pink stem borer (PSB, Sesamia inferens Walker), termites (Microtermes obesi Holmgren and Odontotermes obesus Rambur) and root aphid (Rhopalosiphum rufiabdominalis Sasaki) were undertaken in a rice–wheat cropping system during 2010–11 and 2011–12. Pest abundance and damage was monitored in four tillage systems i.e. conventional tillage (CT), zero tillage (ZT), ZT + mulch and rotary tillage (RT) under insecticide protected and unprotected conditions. The application of insecticide did not affect root aphid incidence or termite damage. However, significant differences in PSB damage in insecticide protected (0.9%) and unprotected (1.2%) conditions were observed. The investigations demonstrated that in CT, damage by PSB (0.6%) was minimum; however termite damage (2.2%) was maximum as compared to all other tillage conditions. In ZT, PSB damage (1.4%) was maximum and root aphid incidence (3.1 aphids/tiller) was minimum in comparison to other tillage conditions. ZT + mulch resulted in inter-mediate insect pest incidence/damage; however, RT was the least effective practice which showed relatively high incidence/damage of these three insects (1.2% PSB damage, 1.9% termite damage and 5.1 aphids/tiller). The insecticide × tillage interaction indicated that insecticide application is needed only in ZT and RT for PSB management.     

Soil organic carbon sequestration as affected by tillage, crop residue, and nitrogen application in rice–wheat rotation system

Despite being a major domain of global food supply, rice?Cwheat cropping system is questioned for its contribution to carbon flux. Enhancing the organic carbon pool in this system is therefore necessary to reduce environmental degradation and maintain agricultural productivity. A field experiment (November 2002?CMarch 2006) evaluated the effects of soil management practices such as tillage, crop residue, and timing of nitrogen (N) application on soil organic carbon (SOC) sequestration in the lowland of Chitwan Valley of Nepal. Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) were grown in rotation adding 12?Mg?ha^?1?y^?1 of field-dried residue. Mung-bean (Vigna radiata L.) was grown as a cover crop between the wheat and the rice. Timing of N application based on leaf color chart method was compared with recommended method of N application. At the end of the experiment SOC sequestration was quantified for five depths within 50?cm of soil profile. The difference in SOC sequestration between methods of N application was not apparent. However, soils sequestered significantly higher amount of SOC in the whole profile (0?C50?cm soil depth) with more pronounced effect seen at 0?C15?cm soil depth under no-tillage as compared with the SOC under conventional tillage. Crop residues added to no-tillage soils outperformed other treatment interactions. It is concluded that a rice?Cwheat system would serve as a greater sink of organic carbon with residue application under no-tillage system than with or without residue application when compared to the conventional tillage system in this condition.     

Effects of combinational treatment with ethephon and gibberellic acid on rice seedling growth and carbohydrate mobilization in seeds under flooded conditions

ABSTRACT

Early seedling growth, including seedling emergence and vigor, is crucial in direct seeded rice. In this study, we examined the effects of gibberellic acid (GA₃) and ethephon (ET) on the early growth of direct seeded rice, and on α-amylase activity and soluble sugar content in the seeds. Rice seeds were treated with water (control), ET, GA₃, or ET+ GA₃ and were allowed to grow for 21 days. The results showed that ET and GA₃ synergistically improved the lengths of mesocotyl, coleoptile, mesocotyl+ coleoptile, and first leaf. Moderate synergistic effects of ET and GA₃ were detected in the second and third leaves. ET+ GA₃ treatment induced higher α-amylase activities during early post-germination growth, which is consistent with the longer coleoptile, mesocotyl, mesocotyl+ coleoptile, and first leaf. In addition, ET+ GA₃ induced higher α-amylase activity in the seeds, and consequently, higher sucrose and glucose concentrations than other treatments. These results partially explain the regulatory mechanism underlying the synergistic interaction of ET and GA₃ on rice seedling growth in terms of starch and sugar metabolism in the seeds, and this knowledge is expected to facilitate the practical use of ET and GA₃ in direct seeded rice systems.     

Influence of field re-ponding pattern and plant spacing on rice root–shoot characteristics,yield, and water productivity of two modern cultivars under SRI management in Indian Mollisols

A 2-year field experiment was conducted during the wet seasons (July–October) of 2008 and 2009 on a Typic Hapludoll Mollisol in Indo-Gangetic Plains Region (IGPR) to: (i) investigate the effects of field water re-ponding intervals and plant spacing on the growth, yield, and water productivity (WP) of two rice cultivars under system of rice intensification (SRI) management, and (ii) assess comparative performance of SRI versus ‘best management practices’(BMP) of rice cultivation. This experiment was designed with 14 treatments, 12 under SRI, and 2 BMP (controls). SRI treatments comprised of 3 irrigation regimes viz, irrigation at 1, 3, and 5 day(s) after disappearance of ponded water (DADPW), 2 plant spacings (20 × 20, 25 × 25 cm), and 2 rice cultivars (Pant Dhan 4 and Hybrid 6444). Two BMP (control) treatments comprised of standard cultivation recommendations for flooding and spacing. The experiment was laid-out in a factorial randomized complete block design with three replications. Statistical analysis of data revealed significant variations in root–shoot characteristics and rice yield under SRI between years, reflecting different rainfall patterns. During 2009, a low rainfall year, the panicle numbers m^?2, dry root weight m^?2, root volume m^?2, filled spikelet number panicle^?1, and filled spikelet weight panicle^?1 were significantly higher, which resulted in a rice grain yield enhancement by 5.1 % over 2008, when there was unusually heavy rainfall. Climate × irrigation regime interaction revealed a non-significant influence of irrigation regimes on growth and yield during 2008, whereas in 2009, irrigation at 1 DADPW and 3 DADPW increased grain yield by 12.8 and 8 %, respectively over 5 DADPW. Better root–zone soil moisture regimes, balancing water, and oxygen availability were responsible for higher yields under irrigation at 1 and 3 DADPW. In 2008, soil moisture content (SMC) in 0–15 cm layer was 91, 86, and 82 % of field capacity (FC) at panicle initiation, and 88, 80, and 77 % at panicle emergence stage when irrigation was at 1, 3, and 5 DADPW, respectively; the lower layers (15–30, 30–45 cm) retained their SMC between 87 and 94 % of FC at both stages. During 2009, SMC in all the three layers at both stages was more than 85 % of FC when irrigating at 1 DADPW, and a little more than 70 % for the 0–15 cm layer and >80 % for the other two layers when irrigation was done at 3 DADPW. SMC dropped to below 60 % of FC in the 0–15 cm layer and remained between 67 and 77 % of FC in the other two layers, with lower yield resulting when irrigations were applied at 5 DADPW. However, WP was the highest with irrigation at 5 DADPW (38.5 kg ha cm^?1). Wider plant spacing (25 × 25 cm) resulted in generally and significantly higher grain yield and WP. On an average, SRI (6.1 t ha^?1) resulted in yield advantage of 0.9 t ha^?1 over BMP (5.2 t ha^?1). Overall, it is inferred that in SRI, wider planting (25 × 25 cm) with field re-ponding at 3 DADPW if there is adequate water availability and at 5 DADPW under limited water supply conditions, may lead to higher rice yields and WP in sub-humid tarai Mollisols of IGPR and comparable agro-climatic conditions in Indian sub-continent.     

Assessment of different methods of rice (Oryza sativa. L) cultivation affecting growth parameters, soil chemical, biological, and microbiological properties, water saving, and grain yield in rice–rice system

Field experiments were conducted at DRR farm located at ICRISAT, Patancheru, in sandy clay loam soils during four seasons, Kharif 2008, Rabi 2008–2009, Kharif 2009 and Rabi 2009–2010, to investigate growth parameters, water-saving potential, root characteristics, chemical, biological, and microbial properties of rhizosphere soil, and grain yield of rice (Oryza sativa L.) by comparing the plants grown with system of rice intensification (SRI) methods, with organic or organic + inorganic fertilization, against current recommended best management practices (BMP). All the growth parameters including plant height, effective tillers (10–45 %), panicle length, dry matter, root dry weight (24–57 %), and root volume (10–66 %) were found to be significantly higher with in SRI-organic + inorganic over BMP. With SRI-organic fertilization, growth parameters showed inconsistent results; however, root dry weight (3–77 %) and root volume (31–162 %) were found significantly superior compared to BMP. Grain yield was found significantly higher in SRI-organic + inorganic (12–23 and 4–35 % in the Kharif and Rabi seasons, respectively), while with SRI-organic management, yield was found higher (4–34 %) only in the Rabi seasons compared to BMP. An average of 31 and 37 % of irrigation water were saved during Kharif and Rabi seasons, respectively, with both SRI methods of rice cultivation compared to BMP. Further, total nitrogen, organic carbon%, soil dehydrogenase, microbial biomass carbon, total bacteria, fungi, and actinomycetes were found higher in the two SRI plots in comparison to BMP. It is concluded that SRI practices create favorable conditions for beneficial soil microbes to prosper, save irrigation water, and increase grain yield.     

Response of N2O emission to straw retention under two contrasting paddy water conditions: a field experiment over rice–rice-fallow rotation

Paddy and Water Environment - Few studies are available on comprehensive impacts of straw retention and water regimes on nitrous oxide (N2O) emission from rice–rice-fallow rotation systems. A...     

Cooperative effects of sand application and flushing during the sensitive stages of rice on its yield in a hard saline–sodic soil

Application of sand can ameliorate rice paddy fields converted from saline–sodic land. However, the requirement of huge amount of sand has been limiting its practical application. In this study, flushing during saline sodic-sensitive stages of rice plant growth was incorporated into the ameliorating system to reduce the sand usage. A split-plot design was adopted with sand application (SA) with two levels as main plots and flushing during the sensitive stages (FL) with two levels as subplots in a hard saline–sodic soil, Northeast China. Four treatments included CK (no-sand, no-flush flooding), NF (non-sand, flush flooding), SN (sand, no-flush flooding), and SF (sand, flush flooding). The results showed that both SA and FL significantly affected all the investigated yield parameters. The combined effect of SA and FL on the grain yield was additive in the first year in respect of the effect on panicle density and seed weight per panicle; while it showed synergistic effect on the seed weight per panicle and grain yield in the second year. The rice yield in different treatments was in the order of SF > SN > NF > CK in both years, with the highest yield (4.37 t ha^?1) obtained by SF treatment in the second year. Our results demonstrate that half the traditional amount of sand in combination with water-flushing during the saline–sodic-sensitive growth stages of rice is sufficiently effective in ameliorating saline–sodic soil and thereby enhancing rice grain yield in saline–sodic paddy fields.     

Effects of 42-year long-term fertilizer management on soil phosphorus availability,fractionation,adsorption–desorption isotherm and plant uptake in flooded tropical rice

Soil phosphorus(P) fractionation, adsorption, and desorption isotherm, and rice yield and P uptake were investigated in flooded tropical rice(Oryza sativa L.) following 42-year fertilizer and manure application. The treatments included low-input [unfertilized control without N, P, or K(C0N0)], farmyard manure(FYM)(C1N0), NP(C0NP), NPK(C0NPK), FYM + NP(C1NP), and high-input treatment, FYM + NPK(C1NPK). Grain yield was increased significantly by 74%over the control under the combined application of FYM + NPK. However, under low- and high-input treatments, yield as well as P uptake was maintained at constant levels for 35 years.During the same period, high yield levels and P uptake were maintained under the C0 NP, C0 NPK,and C1 NPK treatments. These are unique characteristics of a tropical flooded ecosystem, which is a self-sustaining system for rice production. The Fe–P fraction was highest compared to the Ca–P and Al–P fractions after 42 years of fertilizer application and was significantly higher under FYM + NPK treatment. The P adsorption capacity of soil was highest under the low-input treatment and lowest under long-term balanced fertilization(FYM + NPK). In contrast, P desorption capacity was highest under NPK and lowest in the control treatment. Long-term balanced fertilization in the form of FYM + NPK for 42 years lowered the bonding energy and adsorption capacity for P in soil but increased its desorption potential, increasing P availability to the plant and leading to higher P uptake and yield maintenance.