Alleviating soil sickness caused by aerobic monocropping: Responses of aerobic rice to nutrient supply

Yield decline is a major constraint in the adoption of monocropping of aerobic rice. The causes of the yield decline in the continuous aerobic rice system are still unknown. The objective of this study was to determine if nutrient application can mitigate the yield decline caused by continuous cropping of aerobic rice. Micro-plot experiment was conducted in 2005 dry season (DS) in a field where aerobic rice has been grown continuously for eight seasons from 2001 DS at the International Rice Research Institute (IRRI) farm. Pot experiments were done with the soil from the same field where the micro-plot experiment was conducted and aerobic rice has been grown continuously for 10 seasons. Apo, an upland rice variety, was grown under aerobic conditions with different nutrient inputs in field and pot experiments. The field micro-plot experiment showed that micronutrients had insignificant effect on plant growth under continuous aerobic rice cultivation but the combination of N, P, and K mitigated the yield decline of continuous aerobic rice. A series of pot experiments studying the individual effects of nutrients indicated that N application improved plant growth under continuous aerobic rice cropping, while P, K, and micronutrients had no effect. Increasing the rate of N application from 0.23 to 0.90 g per pot in the continuous aerobic rice soil increased the vegetative growth parameters, chlorophyll meter readings, and aboveground N uptake consistently. Our results suggested that N deficiency due to poor soil N availability or reduced plant N uptake might cause the yield decline of continuous cropping of aerobic rice.     

Causes for soil sickness affecting early plant growth in aerobic rice

In aerobic rice, adapted varieties are grown in non-flooded and non-saturated soil. In the Philippines, occasional poor crop growth and yield failures have been reported. To investigate the underlying causes, we conducted 3 pot experiments using the aerobic rice variety Apo and so-called “sick soil” from a field where aerobic rice failed in four successive dry seasons. The (experimental) aerobic rice crop replaced the farmer's practice of wet-season lowland rice and dry season sweet potato cropping. We hypothesized that abiotic factors, especially the inter-relationship between high soil pH and impaired micronutrient uptake, restrict plant growth, and that ammonium sulfate has an ameliorating effect. Experiment 1 used “sick soil” collected from around yellowing and dying plants in a field experiment with aerobic rice yield failure, and “healthy soil” collected from around well-growing plants in the same field. We used three N fertilizer treatments (ammonium sulfate, urea, no application) and two soil water conditions (well drained and water-logged). In experiment 2, the treatments were a combination of sick and healthy soil, N fertilizer, soil acidification, and foliar application of Fe. Experiment 3 compared the irrigation water used at the experimental field site with reverse-osmosis water. Irrigation with water from the field site increased soil pH, impaired plant growth, and induced chlorosis. The application of ammonium sulfate reduced soil pH to values below 6 and increased plant micronutrient (Fe, Mn and Zn) contents and plant growth. In early vegetative plant growth, the high soil pH appeared to be the key determinant of “sick soil”, while root knot nematodes were most likely secondary causes for poor plant growth.     

氮肥管理对稻虾共作模式水稻产量和抗倒伏特性的影响

通过设置不同稻作模式（水稻单作、稻虾共作）和氮肥管理（不施氮、常规施氮、减氮）两因素交互试验,研究氮肥管理对稻虾共作模式水稻产量及抗倒伏特性的影响。结果表明,稻虾共作模式下常规施氮和减氮处理的水稻产量分别为7 539 kg/hm²和7 328 kg/hm²,比水稻单作模式降低29.4%~32.3%,这主要是由于试验当年水稻移栽后连续降雨导致缓苗不利所致,也与深水淹灌下水稻有效穂数、每穗粒数和千粒重下降有关。相比水稻单作,稻虾共作模式下水稻茎秆的株高、穂颈高、重心高、弯曲力矩和倒伏指数平均增加12.9%、17.9%、8.0%、20.9%和33.5%,第2节间茎壁厚、抗折力和折断弯矩平均降低38.7%、16.8%和16.6%。在稻虾共作模式中,与常规施氮处理相比,减氮处理仅减产2.9%,水稻茎秆抗折力增加13.5%、倒伏指数降低1.8%。相关分析表明,茎壁厚度与倒伏指数呈极显著负相关（p<0.01）,株高和弯曲力矩与抗折力呈显著负相关（p<0.05）。稻虾共作模式可保证水稻稳产,氮肥减施有助于提高该模式下水稻抗倒伏能力,降低倒伏风险。     

Rice Uptake and Recovery of Nitrogen with Different Methods of Applying 15N-Labeled Chicken Manure and Ammonium Sulfate

Abstract

The effects of different methods of fertilization on rice uptake and recovery of nitrogen were studied using ¹⁵N-lablled chicken manure (CM) and ammonium sulfate (AS). The results showed that the application method of totally basal dressing of organic and inorganic fertilizers can increase the N uptake by rice from the fertilizers. The N uptake from CM was obviously higher than that from AS. The N partitioning to rice grain was also higher than other application methods. The effect on increasing yield was obviously higher than the method of application of chemical fertilizers only. This method had such benefits as increasing N use efficiency, increasing N residue in soil and reducing N loss. High rice yield can be obtained while the soil fertility can be maintained with this method. So it is an effective and practical method of fertilization technique thus can be recommended to rice growers.     

Effects of Water-Saving Irrigation and Nitrogen Fertilization on Yield and Yield Components of Rice (Oryza sativa L.)

Abstract

The effects of nitrogen (N) application (32, 72 and 112 kg N ha-¹ in 2000, and 32, 92 and 152 kg N ha-¹ in 2001) and water-saving irrigation and their interaction on grain yield and yield components of the rice cultivar Champa-Kamphiroozi, which is a local cultivar in a semi-arid area in the south of Islamic Republic (I.R.) of Iran, were investigated. The plants were cultivated under sprinkler irrigation (1.0 ET_p and 1.5 ET_p), intermittent flooding (1-day and 2-day intervals) and continuous flooding (control). The experiments were conducted on a clay loam-clay soil under a semi-arid environment using four replications in a split plot design with irrigation method as main plots and N levels as subplots. The results indicated that intermittent flooding irrigation at 2-day intervals was as effective as continuous flooding for grain yield, showing high water-use efficiency (WUE). The soil moisture tension in the root zone before each irrigation under this condition was –300 to –400 cm. Sprinkler irrigation and intermittent flooding increased WUE by 20 to 60%, compared with continuous flooding, and the increase in N application rate to 112-152 kg ha-¹ increased grain yield under any irrigation condition. Under sprinkler irrigation, grain yield was low and percentage of unfilled grain was high, although WUE was high. However, by adopting sprinkler irrigation, the amount of nitrogen fertilizer application necessary for cultivation was reduced. Furthermore, when nitrogen application must be limited due to groundwater pollution, the amount of nitrogen fertilizer necessary for cultivation can be reduced.     

施用土壤酸化剂和调整播期防治膜下滴灌水稻苗期缺铁黄化的效果研究

黄化是石灰性土壤上水稻膜下滴灌常见的营养障碍,显著影响作物生长发育和产量。以水稻品种T-43为试验材料,采用两因素裂区试验研究播期和土壤局部酸化对改善膜下滴灌水稻苗期缺铁黄化的作用。主区设置三种不同的播期,即在土温达到12℃(T1)、15℃(T2)、18℃(T3)时播种;副区为不同的土壤酸化剂:硫酸铵+硝化抑制剂(AS)、磷酸(PP)、柠檬酸(CA)和对照(CK)。结果表明,三种酸化剂处理均显著降低土壤pH值,提高了土壤有效铁含量,其中AS效果最显著。AS、PP和CA处理的苗期水稻叶片中有效铁含量较CK分别提高14.4%、11.3%和9.2%。三种酸化剂提高了水稻苗期根系活力和根系的根长、表面积、根体积,以AS处理效果最好。晚播较早播显著提高了水稻苗期根系活力,增加了水稻根系的根长、表面积、根体积。晚播使水稻苗期叶片活性铁含量提高了11.2%,叶片SPAD值显著增加。酸化剂的施用有助于克服水稻苗期缺铁黄化,以硫酸铵(生理酸性盐)结合硝化抑制剂最佳,适当的推后播期也能有效改善膜下滴灌水稻缺铁黄化。     

Improvement of Rice Seedling Establishment in Sulfate-Applied Submerged Soil by Application of Molybdate

Abstract

Sulfide ion generation in strictly reduced soil might be a factor impairing rice seedling establishment. The molybdate ion is known to suppress the microbial transformation of sulfide ions from sulfate ions. I investigated the effect of molybdate on rice establishment in sulfate-applied submerged soil. The establishment of rice seeds sown in sulfate-applied submerged soil was markedly improved by application of potassium molybdate at a rate of 1.5?15 mmol kg-¹ dried soil. The application of potassium molybdate delayed the decline of the sulfur concentration in the soil solution near the seeds and the appearance of circular black stains, or insoluble iron sulfide indicating the generation of sulfide ion, around seeds in the soil. Irrespective of the application of molybdate, the redox potential near the seeds was low enough to allow generation of sulfide ions, implying that molybdate suppresses the generation of sulfide ions with no effect on redox potential. These results suggest that the application of molybdate could improve rice seedling establishment in sulfur-rich submerged soil by suppressing the generation of sulfide ions, that is a possible factor suppressing the establishment of rice seeds sown in sulfur-rich submerged soil.     

Biotic and abiotic causes of yield failure in tropical aerobic rice

Aerobic rice is a new production system for water-short environments. Adapted varieties are usually direct dry seeded and the crop grown under aerobic soil conditions with supplementary irrigation as necessary. Occasionally, yield failures occur which may be related to soil health problems. In the dry season of 2006 and 2007, we conducted a field experiment in the Philippines, to identify the major causes of such yield failure. Four treatments were implemented: (i) Control of direct dry-seeded rice (improved upland variety Apo), (ii) Biocide application, (iii) transplanting into aerobic soil, and (iv) 1 year fallow. Yield in the Biocide treatment was 2 t ha⁻¹ in both years. In all other treatments, yield was 0–0.3 t ha⁻¹. Plants grown in the Biocide treatment showed a reduced degree of galling of roots caused by root-knot nematodes (RKN) and better general root health than the Control treatment. Potentially pathogenic fungi were isolated from root samples (Pythium sp., Fusarium sp., and a Rhizoctonia-like species). Abiotic effects of the Biocide treatment were an increase in KCl-extractable N (initial season 2007) and a decrease in initial soil pH. In the Control treatment, soil pH increased from 6.5 to 8.0 over the two seasons. In 2007, plant tissue analysis indicated Mn deficiency in the Control treatment. Plants that were subjected to foliar micronutrient sprays reacted positively to Fe and Mn sprays in the Control treatment, and Mn spray in the Biocide treatment. We concluded that the Biocide application led to favorable soil conditions by reducing biotic stresses such as RKN and improving nutrient availability. In the other treatments, an interaction of RKN and micronutrient deficiencies with increasing soil pH led to yield failure.     

Effects of water management and organic fertilization with SRI crop practices on hybrid rice performance and rhizosphere dynamics

A field experiment was conducted to investigate the effects of intermittent versus continuous irrigation, together with different degrees of organic fertilization, on the growth and yield of hybrid rice, looking also at the functioning of the rhizosphere as this is a key element affecting crop performance. The crop management practices employed generally followed the recommendations of the System of Rice Intensification (SRI). The aim of the research was to learn how water management and organic fertilization together would affect crop outcomes. Under intermittent water application as recommended with SRI management (aerobic irrigation, AI), grain yield increased by 10.5–11.3%, compared to standard irrigation practice (continuous flooding, CF). The factor that contributed most to higher yield was increased number of grains per panicle. It was seen that under the range of organic fertilization treatments evaluated, intermittent irrigation compared with CF promoted greater dry matter production and higher leaf area index (LAI) during the main growth stages. Also, the combination of intermittent irrigation and organic material applications significantly increased soil redox potential (Eh), compared with CF, and also the numbers of actinomycetes in the rhizosphere soil. Actinomycetes were evaluated in this study as an indicator of aerobic soil biota. It was seen that with intermittent irrigation, the application of organic material improved the functioning of the rhizosphere and increased yield. However, these results based on 2 years of study reflect relatively short-term effects. The effects of longer-term water management and soil fertilization regimes should be also examined, to know whether these effects continue and, if they do, whether they become greater or less.     

【Short Report】Grain Yield and Leaf Area Growth of Direct-Seeded Rice on Flooded and Aerobic Soils in Japan

Abstract

Direct-seeding has been proposed as a water- and labor-saving method to grow irrigated rice. Our objective was to compare the effects of flooded and aerobic conditions on the yield stability of direct-seeded rice. We set up four trials in the field: aerobic, near-saturated and flooded soils with direct seeding, and flooded soil with transplanting. Grain yield of direct-seeded rice was comparable to that of transplanted under flooded conditions. However, the yield of direct-seeded rice under aerobic conditions was up to 21% lower than that under flooded conditions. This poor performance was associated with reduced leaf growth during the vegetative stage. Our results indicate that the yield stability of direct-seeded rice could be lowered by the water-saving irrigation, compared with the conventional flooded culture. In order to save irrigation water, physiological research on direct-seeded rice should target the vulnerability of rice to aerobic soils or to soil moisture fluctuations.     

不同水分管理条件下蚓粪对水稻镉积累的影响

通过盆栽试验,研究了在淹水灌溉和湿润灌溉条件下蚓粪施用对土壤理化性质及水稻积累镉的影响.结果表明,湿润灌溉下土壤pH值高于淹水灌溉,蚓粪加速了淹水灌溉下土壤Eh值的下降;淹水灌溉下土壤Fe2+含量显著高于湿润灌溉,蚓粪的施用进一步提高了土壤Fe2+含量;与不施蚓粪相比,淹水灌溉下施用蚓粪显著降低了土壤DTPA-Cd含量...     

Effect of Field Drainage on Root Lodging Tolerance in Direct-Sown Rice in Flooded Paddy Field

Abstract

To elucidate the effect of drainage of paddy fields on root lodging tolerance in direct-sown rice, we measured the pushing resistance (R), diameter of hill at the base (Dm), shoot dry weight (Ws) and root dry weight (Wr), in rice varieties grown using several irrigation management schemes that differed in the frequency and length of field drainage during the growing season. Soil hardness was also monitored to investigate the relationship between the variance of soil physical properties caused by different irrigation treatments and root lodging tolerance. Pushing resistance moment (Rh), i.e., product of pushing resistance (R) and height of pushed part of hill (h), showed higher values in rice grown in fields drained more frequently or for longer periods. A similar pattern was found in rice grown in field plots where root penetration to the subsoil layers was prevented by laying an unwoven cloth between the topsoil and subsoil layers. Higher values for pushing resistance efficiency based on root dry weight (Kr : Rh/Wr/Dm) were also found in plots subjected to more frequent or prolonged drainage, irrespective of rice variety. Soil hardness was progressively increased by each field drainage during the growing season, and showed a highly significant relationship with Kr. The above results suggest that field drainage increases the root lodging tolerance in direct-sown rice through improvement of anchoring ability caused by increased soil hardness.     

Rhizosphere Aeration Improves Nitrogen Transformation in Soil,and Nitrogen Absorption and Accumulation in Rice Plants

Two rice cultivars (Xiushui 09 and Chunyou 84) were used to evaluate the effects of various soil oxygen (O₂) conditions on soil nitrogen (N) transformation, absorption and accumulation in rice plants. The treatments were continuous flooding (CF), continuous flooding and aeration (CFA), and alternate wetting and drying (AWD). The results showed that the AWD and CFA treatments improved soil N transformation, rice growth, and N absorption and accumulation. Soil NO₃^– content, nitrification activity and ammonia-oxidising bacteria abundance, leaf area, nitrate reductase activity, and N absorption and accumulation in rice all increased in both cultivars. However, soil microbial biomass carbon and pH did not significantly change during the whole period of rice growth. Correlation analysis revealed a significant positive correlation between the nitrification activity and ammonia-oxidising bacteria abundance, and both of them significantly increased as the total N accumulation in rice increased. Our results indicated that improved soil O₂ conditions led to changing soil N cycling and contributed to increases in N absorption and accumulation by rice in paddy fields.     

秸秆覆盖下旱作水稻的生长发育特征研究

通过半腐解秸秆覆盖旱作、地膜覆盖旱作、裸地旱作比较试验,研究了在田间覆盖条件下旱作水稻的生长发育以及产量形成特征。结果表明,在水稻生长期,降雨量为440 mm条件下,与其他旱作相比,采用半腐解秸秆覆盖,水稻生育前期植株个体生长受到一定抑制,但生育中后期有利于水稻植株的生长发育,分蘖成穗率较高,冠层叶长,叶面积大,光合功能强,每穗结实粒数多,粒重大,产量高。     

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.     

Role of early vigor in adaptation of rice to water-saving aerobic culture: Effects of nitrogen utilization and leaf growth

Early vigor and rapid canopy development are important characteristics in aerobic rice culture, where they are highly susceptible to soil water deficits. To elucidate the response of rice's vegetative growth to water management regimes, we evaluated the leaf growth and the concomitant nitrogen (N) utilization of nine cultivars grown in flooded and aerobic culture in 2 years. In aerobic culture, the soil water potential at a depth of 20 cm frequently reached −60 kPa in 2007, but remained above −30 kPa in 2008. The average leaf area index (LAI) in the middle of the vegetative growth stage, N uptake and leaf N content per unit leaf area (specific leaf N; SLN) in aerobic culture were comparable to those in flooded culture. However, there was a significant cultivar × water regime interaction in LAI: cultivars with higher LAI during the vegetative growth stage achieved higher yield in aerobic rice culture. IR72 and Takanari (high-yielding cultivars of flood-irrigated rice) showed poor leaf growth as well as lower N uptake and higher SLN in aerobic culture compared with flooded culture. Our results show that early vigor is closely associated with yield stability to the soil moisture fluctuations in aerobic rice culture, even if weeds are properly controlled. Greater N uptake from aerobic soil and better balancing between the N demand for leaf growth and the N supply to the leaves under fluctuating soil moisture would be, at least in part, relevant to a rice cultivar's adaptation to aerobic conditions.     

Intermittent drainage in paddy soil: ecosystem carbon budget and global warming potential

Intermittent drainage of rice fields alters soil redox potential and contributes to the reduction of CH₄ emission and thus may reduce net global warming potential (GWP) during rice cultivation. Incorporation of green biomass helps maintaining soil organic matter, but may increase CH₄ emission. We investigated net ecosystem carbon budget (NECB) and net GWP under two water management regimes—continuous flooding and intermittent drainage—having four biomass incorporation levels (0, 3, 6 and 12 Mg ha^?1). Water management and biomass incorporation level demonstrated significant (P < 0.05) interaction effect on the NECB and GWP. Intermittent drainage decreased the NECB by ca. 6–46 % than continuous flooding under same rates of cover crop biomass (CCB) incorporation. Moreover, intermittent drainage reduced seasonal CH₄–C fluxes by ca. 54–58 % and net GWP by 35–58 % compared to continuous flooding. There was also no significant reduction in rice yield because of intermittent drainage under similar CCB. This implies that incorporation of 3 Mg ha^?1 CCB and intermittent drainage could be a good option for reducing net GWP and higher grain yield.     

Alleviative effects of mixed-cropping with rice on the growth inhibition of pearl millet caused by flooding at reproductive stage

Flooding has globally become common, and thus cultivation techniques to adapt to the stress are required. We have developed a technique called “close mixed-planting” using flood-adapted rice (Oryza sativa L.) and upland crops with tangled root systems, showing that this technique can mitigate the damage caused to upland crops by flooding. However, the plant response during the reproductive stage has not yet been examined. In this study, we estimated the alleviative effects of close mixed-planting on the growth inhibition and physiological damage to pearl millet (Pennisetum glaucum) caused by flooding at the reproductive stage in northern Namibia. Pearl millet and NERICA4 (Oryza spp., interspecies of O. sativa and O. glaberrima) were used. Four-week-old single- and mixed-crop pearl millets were transplanted and grown for 22 days, and then flooding treatment was administered for 28 days. The growth and physiological parameters of single pearl millet were significantly decreased by flooding stress, and the parameters did not recover during a 14-day recovery period compared with those of unflooded single and mix-cropped pearl millet. On the other hand, the damage to mix-cropped pearl millet by flooding was suppressed. Thus, the mixed-cropping mitigated the anoxic stress of pearl millet caused by flooding at the reproductive stage and contributed to the improved growth after the recovery period. This result suggested that the close mixed-planting with rice can contribute to the mitigation of flooding damage not only at the vegetative stage but also at the reproductive stage of pearl millet in the semi-arid African country, Namibia.     

Manganese nutrition improves the productivity and grain biofortification of fine grain aromatic rice in conventional and conservation production systems

Manganese (Mn) deficiency is prevalent in rice-growing regions resulting in poor paddy yield and human health. In this study, role of Mn, applied through various methods, in improving the productivity and grain biofortification of fine grain aromatic rice was evaluated. Manganese was delivered as soil application (SA) (0.5 kg ha^?1), foliar spray (FA) (0.02 M Mn), seed priming (SP) (0.1 M Mn) and seed coating (SC) (2 g Mn kg^?1 seed) in conventional (puddled transplanted flooded rice) and conservation (direct seeded aerobic rice) production systems at two different sites (Faisalabad, Sheikhupura) in Punjab, Pakistan. Manganese application, through either method, improved the grain yield and grain Mn contents of fine grain aromatic rice grown in both production systems at both sites. However, Mn application as SC and FA was the most beneficial and cost effective in improving the productivity and grain biofortification in this regard. Overall, order of improvement in grain yield was SC (3.85 t ha^?1) > FA (3.72 t ha^?1) > SP (3.61 t ha^?1) > SA (3.36 t ha^?1). Maximum net benefits and benefit–cost ratio were obtained through Mn SC in flooded field at Faisalabad, which was followed by Mn SP in direct seeded aerobic rice at the same site. However, maximum marginal rate of return was noted with Mn SC in direct seeded aerobic rice at both sites. In crux, Mn nutrition improved the productivity and grain biofortification of fine grain aromatic rice grown in both conventional and conservation production systems. However, Mn application as seed treatment (SC or SP) was the most cost effective and economical.     

Field Evaluation of Coffee Grounds Application for Crop Growth Enhancement,Weed Control,and Soil Improvement

Abstract

The use of coffee grounds in crop fields were evaluated in terms of crop growth enhancement, soil improvement, and weed control during four successive cropping seasons for two years. Six summer and three winter green manure crops were grown from June 2009 to May 2011. In the first cropping season, the growth of all green manure crops was significantly inhibited by the application of 10 kg m^–2 of coffee grounds. However, the inhibitory effects spontaneously diminished after the second cropping season (about 12 months later), and the growth of guinea grass, sorghum and sunflower was about 2-fold higher than that of the control. The application of horse manure at 10 kg m^–2 effectively alleviated the inhibitory effects, even though the high concentration of coffee grounds was included. Although top dressing application of coffee grounds at 16 kg m^–2 permitted weed control, the impact maintained enough only for half a year. Coffee grounds application effectively increased both carbon and nitrogen contents of soil and reduced CN ratio. The soil amendment effects were significantly higher in terms of nitrogen enrichment and CN ratio improvement as compared with the horse manure application. These results indicated that coffee grounds are useful to enhance long term crop growth, short duration weed control, and soil improvement in agricultural fields by considering the inhibitory effects on the plant growth for half year after the application. Agricultural use of coffee grounds was also discussed in term of fallow periods in crop rotation.