PH—Postharvest Technology: Airflow Resistance of Green Gram

Pressure drops were measured in clean green gram beds at moisture content in a range of 8·36–16·65% d.b. for superficial air velocities which ranged between 0·0104 and 1·0875 m³ s⁻¹ m⁻² at bed depths of 0·2 to 0·6 m with bulk density ranging from 760 to 855 kg m⁻³. The airflow resistance of green gram increased with the increase in airflow rate, bulk density, bed depth and decreased moisture content. Results indicated that 1% increase in moisture content decreased the pressure drop by 2·43% whereas, 1% increase in bulk density increased the pressure drop by 6·6%. Modified Shedd's equation, Hukill and Ives equation and modified Ergun equation all with two parameters were examined. Airflow resistance was accurately described by modified Shedd's equation and an empirical equation, composed of airflow rate, moisture content and bulk density.     

PH—Postharvest Technology: Physical Properties of Okra Seed

The physical properties of okra seed were evaluated as a function of moisture content (m.c.). The average length, breadth and thickness of the seed varied from 5·92 to 7·30, 4·71 to 5·40 and 4·59 to 5·36 mm, respectively, as the moisture content increased from 8·16 to 87·57% d.b. The roundness and sphericity increased from 77·76 to 79·35% and 74·48 to 76·52%, respectively, with increase in moisture content from 8·16 to 19·56% d.b. and then decreased to 72·39 and 70·63%, respectively, with further increase of moisture content. In the moisture range of 8·16–87·57%, the seed volume increased from 0·067 to 0·124 cm³, 1000 seed weight, W₁₀₀₀ from 65·78 to 129·75 g and the angle of repose from 27·60 to 39·47°. The bulk density, true density and porosity decreased from 0·592 to 0·558 g cm⁻³, 1·107 to 0·986 g cm⁻³ and 46·34 to 43·20%, respectively, in the moisture range from 8·16 to 87·57% d.b. The static coefficient of friction increased on four structural surfaces namely, aluminium (0·390–0·484), bakelite (0·345–0·480), galvanised iron (0·368–0·493) and mild steel (0·389–0·480) as the moisture content increased from 8·16 to 87·57% d.b.     

Physical Properties of Vetch Seed

The physical properties of vetch seed were evaluated as a function of moisture content. The average length, width and thickness were 5·19, 4·33 and 3·63 mm, respectively, at 10·57% dry basis (d.b.) moisture content. In the moisture range from 10·57 to 20·63% d.b., studies on rewetted vetch seed showed that the thousand seed mass increased from 55·47 to 59·03 g, the projected area from 23·52 to 29·05 mm², the sphericity from 0·837 to 0·859, the true density from 1286·2 to 1369·9 kg m⁻³, the porosity from 33·08% to 39·68% and the terminal velocity from 9·94 to 10·33 m s⁻¹. The static coefficient of friction of vetch seed increased the linearly against surfaces of four structural materials, namely, rubber (0·350–0·387), aluminium (0·319–0·367), stainless steel (0·202–0·328) and galvanised iron (0·312–0·361) as the moisture content increased from 10·57 to 20·63% d.b. The bulk density and the shelling resistance decreased from 860·8 to 826·2 kg m⁻³ and from 148·73 to 62·68 N, respectively, with an increase in moisture content from 10·57 to 20·63% d.b.     

PH—Postharvest Technology: Thermodynamics of Moisture Sorption in Sesame Seed

Experimental data on the sorption isotherms of sesame seed were used to determine the thermodynamic functions (heat of vaporisation, spreading pressure, net integral enthalpy and entropy). The heat of vaporisation decreased with increase in moisture content and approached the latent heat of pure water at moisture content between 18 and 21% dry basis. The spreading pressure increased with increase in water activity and was not significantly affected by temperature. Net integral enthalpy decreased with increase in moisture content, and became asymptotic as the moisture content of 12% was approached. Net integral entropy decreased with increase in moisture content to a minimum value of 0·138 J kg⁻¹K⁻¹ at moisture content of about 3·7%. It then increased with moisture content to a maximum of about 0·63 J kg⁻¹K⁻¹ at about 12% moisture content and thereafter, remained nearly constant.     

Mathematical Modelling of Vacuum Pressure on a Precision Seeder

The purpose of this research was to determine the optimum vacuum pressure of a precision vacuum seeder and to develop mathematical models by using some physical properties of seeds such as one thousand kernel mass, projected area, sphericity and kernel density. Maize, cotton, soya bean, watermelon, melon, cucumber, sugarbeet and onion seeds were used in laboratory tests. One thousand kernel mass, projected area, sphericity and kernel density of seeds varied from 4·3 to 372·5 g, 5–77 mm², 38·4–85·8% and 440–1310 kg m⁻³, respectively. The optimum vacuum pressure was determined as 4·0 kPa for maize I and II; 3·0 kPa for cotton, soya bean and watermelon I; 2·5 kPa for watermelon II, melon and cucumber; 2·0 kPa for sugarbeet; and 1·5 kPa for onion seeds.The vacuum pressure was predicted by mathematical models. According to the results, the final model could satisfactorily describe the vacuum pressure of the precision vacuum seeder with a chi-square of 2·51×10⁻³, root mean square error of 2·74×10⁻² and modelling efficiency of 0·99.     

Evaluation of Air Oven Moisture Content Determination Methods for Rough Rice

The effects of air oven drying temperature and drying duration on moisture content determination of medium grain rough rice were studied for moisture content levels from 10·2 to 32·5% (w.b.). Six different methods were compared in this study. A moisture content determination model for an air oven was developed to describe the effect of drying temperature, drying time, and sample grinding on moisture content determination. Drying whole kernels for 72 h at 105°C had the smallest standard deviation. Regression equations obtained from the measured data were used to validate the model developed in this study. This model could be employed to evaluate the moisture determination methods for other varieties of rough rice and other crops obtained from previous literature.     

Soil properties, crop productivity and irrigation effects on five croplands of Inner Mongolia

In the Horqin Sand Land, more than half of the original pasture area has been converted to farmland over the last century. A field experiment was conducted from 2000 to 2001 on five croplands in the Horqin Sand Land of Inner Mongolia to examine differences in soil properties, crop productivity and irrigation effects across different soils in the region to assess their relative suitability for cultivation, in the face of continued pressure for conversion of these generally fragile, sandy soils to agriculture.Two irrigated croplands studied were originally sandy meadow (ISM) and sandy grassland (ISG), and three dry croplands were from sandy meadow (DSM), sandy grassland (DSG) and fixed sand dunes (DFD). Results showed that most measured properties of soils, and crop productivity, differed among the five croplands. The silt + clay fraction, bulk density, organic matter content, total N and P, available N and P, average soil moisture and temperature, plant height and aboveground biomass were as follows in the DSM|DSG|DFD soils: 51.1%|47.5%|24.3%; 1.44 g/cm³|1.49 g/cm³|1.58 g/cm³; 6.3 g/kg|4.6 g/kg|3.4 g/kg; 0.55 g/kg|0.33 g/kg|0.21 g/kg; 0.21 g/kg|0.17 g/kg|0.13 g/kg; 27.0 mg/kg|13.7 mg/kg|7.7 mg/kg; 2.9 mg/kg|2.9 mg/kg|3.0 mg/kg; 9.4%|7.0%|6.2%; 21.4 °C|21.7 °C|22.0 °C; 225 cm|220 cm|181 cm; and 2116 g/m²|1864 g/m²|1338 g/m². Corresponding values for ISM|ISG soils were: 54.3%|47.9%; 1.42 g/cm³|1.49 g/cm³; 8.5 g/kg|6.4 g/kg; 0.58 g/kg|0.42 g/kg; 0.20 g/kg|0.19 g/kg; 29.0 mg/kg|23.3 mg/kg; 4.7 mg/kg|7.9 mg/kg; 13.0%|10.1%; 21.0 °C|21.1 °C; 266 cm|245 cm; and 2958 g/m²|2702 g/m².In general, the ecological origin of a cropland was a stronger determinant of its current characteristics than was irrigation history, although irrigation was correlated with significantly increased organic matter content, some soil nutrient levels, and aboveground biomass productivity. Results indicate that fixed sand dunes should not be converted to cropland because of their very sandy and poorer soil, lower biomass productivity and greater wind-erosion risk. Although both the sandy meadow and sandy grassland may be reclaimed for farming, the cropland derived from the sandy meadow had higher resistance to wind erosion and higher crop productivity, so is somewhat more suitable than sandy grassland.     

SE—Structures and Environment: Biofiltration of Odour and Ammonia from a Pig Unit—Biofiltration of Odour and Ammonia from a Pig Unit—a pilot-scale Study

A pilot-scale biofiltration unit was constructed at a pig finishing building on the University College Dublin research farm. The biofiltration system was investigated over three trial periods. Exhaust air from a single pen was extracted by a variable speed centrifugal fan and passed through a humidifier and biofilter. A 0·5 m depth of woodchips of over 20 mm screen size was used as the biofilter medium. The moisture content of the medium was maintained at 64±4% (wet weight basis) for trial one and 69±4% (wet weight basis) for trials two and three using a load cell method. The volumetric loading rate varied from 769 to 1898 m³ [air] m⁻³ [medium] h⁻¹ during the three trial periods. Odour and ammonia removal efficiencies ranged from 77 to 95% and 54 to 93%, respectively. The pH of the biofilter leachate remained between 6 and 8 throughout the experimental periods. The pressure drop across the biofilter ranged from 14 to 64 Pa. It is concluded that a wood chip media particle size >20 mm is suitable for use in biofiltration systems on intensive pig production facilities. This will minimize the pressure drop on the system fans to reduce overall operation costs. It is recommended that a filter bed moisture content (wet weight basis) of greater than 63% be used to maintain overall efficiency. An efficient air moisturizing system (humidification and bed sprinkling) along with a properly designed air distribution system must be incorporated in the overall design when operating at such high volumetric loading rates.     

Shrinkage Evaluation of Five Different Varieties of Coffee Berries during the Drying Process

The objective of this work was to evaluate the effect of moisture content variation on reduction of superficial area, volume and equivalent sphere diameter of coffee berries. Four varieties of Coffea arabica (cv Catuaí Vermelho, Catuaí Amarelo, Mundo Novo and Catimor) and one variety of Coffea canephora (cv Conilon) were used. From the results obtained, it was concluded that moisture content in the coffee berries affects its physical properties causing significant decrease of the superficial area, volume and diameter of the equivalent sphere during a drying process. The varieties of coffee had different shrinkage behaviour. The Conilon coffee had the highest level of berry shrinkage, the volume decreased 35% during the drying process from 1·38 to 0·12 dry basis (d.b.) berry moisture content. The shrinkage behaviour during the drying process was well explained by a polynomial model with coefficient of determination greater than 90%.     

库布齐沙漠植被恢复对风沙土壤碳通量与碳储量的影响

为阐明库布齐沙漠植被恢复过程中土壤碳通量的时空动态特征及主控因子，明确土壤有机碳含量和储量的变化趋势，本研究以流动沙地、半固定沙地、藻结皮固定沙地和地衣苔藓混合结皮固定沙地为研究对象，运用静态暗箱–气相色谱法对风沙土壤碳通量及水热因子进行观测，并对土壤有机碳含量和密度进行测定和计算。结果表明，生长季内风沙土壤碳通量变异较大，季节动态与土壤温度基本一致，且随植被恢复碳通量呈递增趋势：混合结皮固定沙地(210.28 mg/(m~2·h))>藻结皮固定沙地(177.45 mg/(m~2·h))>半固定沙地(117.34 mg/(m~2·h))>流动沙地(65.61mg/(m~2·h))；土壤碳通量与各层土壤温度均显著正相关，除流动沙地土壤碳通量与深层土壤含水量显著负相关外，其余样地碳通量均与表层土壤含水量显著负相关；风沙土壤有机碳含量和密度随植被恢复而递增：混合结皮固定沙地(1.32 g/kg,0.94 kg/m~2)>藻结皮固定沙地(1.03 g/kg,0.74 kg/m~2)>半固定沙地(0.45 g/kg,0.36 kg/m~2)>流动沙地(0.27...     

不同生长时期极端降水事件对人工针叶林净生产力的影响——以江西省吉安市千烟洲生态试验站为例

[目的]研究不同生长时期极端降水事件对生态系统碳通量的影响,为准确评估江西省吉安市千烟洲人工针叶林生态系统应对极端天气的响应机制提供理论基础。[方法]对比2008年与2010年植物生长初期(4月)与生长旺盛期(6月)碳通量对环境因子(净辐射RN、温度TA、土壤含水量SWC与增强型植被指数EVI)变化的响应差异。[结果] 4月份净生态系统生产力(NEP)降低22.87%,主要是初级生产总量和生态系统呼吸分别降低17.36%[GEP, 9.56 g/(m~2·d)]和2.84%[RE,2.86 g/(m~2·d)]导致,而6月份GEP降低3.58%[7.17 g/(m~2·d)]以及RE增长12.8%[20.37 g/(m~2·d)]导致NEP降低65.77%[27.55 g/(m~2·d)]。[结论]生长季初期TA降低对RE的抑制大于土壤含水量增加的影响,而生长旺盛期土壤含水量增加则会抵消降温对呼吸的抑制,造成更大的碳损失,因此后续研究森林生态系统碳通量对极端气候响应时还需要考虑植物生长时期的影响。     

PH—Postharvest Technology: Diffusive Drying Kinetics in Wheat,Part 2: applying the Simplified Analytical Solution to Experimental Data

Reanalysis of the drying background in wheat showed that analytical solutions may be employed in this grain to estimate diffusion coefficients by using the simplified equation for short times instead of the time-consuming series. Sixteen thin-layer drying curves of hard wheat were measured (airflow ≈ 0·3 kg m⁻²s⁻¹) covering four air temperatures (35–70°C) at each of four initial moisture content levels (0·189–0·269 decimal, d.b.). Experimental curves of the moisture ratio versus time grouped by initial moisture content showed the expected strong accelerating effect of temperature on drying rate. Besides, when the same curves were grouped by temperature, the moisture ratios corresponding to higher initial moisture contents fell, after some time, consistently faster, showing that the diffusion coefficient should increase somehow with water concentration. The short time simplified diffusive equation fitted each curve very well, with values of the coefficient of determination above 0·99. Values of the diffusion coefficient for the whole kernel ranged from 1·4×10⁻¹¹to 7·1×10⁻¹¹m⁻²s⁻¹, presenting the classical Arrhenius temperature dependency (activation energy ≈ 27·0 kJ mol⁻¹), but with a pre-exponential factor that depends linearly on initial moisture content. This diffusive kinetics is expected to be useful for fast and accurate dryer simulation.     

Estimation of economic threshold level of alligator weed (Alternanthera philoxeroides (Mart.) Griseb.) to Tackle Grain quality and yield Losses in Rice

Alligator weed (Alternanthera philoxeroides) is the most troublesome invasive weed in transplanted rice ecosystems worldwide. A two-year field study was conducted to estimate economic threshold levels and the season long competitive effect of six alligator weed densities (0, 2, 4, 8, 16, and 32 plants m^?2) on yield and quality traits of transplanted rice. A gradual linear incline in dry weight of alligator weed was observed with an increase in its density from 2 to 32 plants m^?2. Maximum N (15.93–18.26 kg ha^?1), P (15.10–16.46 kg ha^?1) and K (16.34–17.81 kg ha^?1) uptake by alligator weed was recorded at its density of 32 plants m^?2. More micronutrient loss to the tune of 6.53, 47.92, 19.99, and 38.42 mg kg^?1 for Cu, Fe, Zn, and Mn, respectively was observed at the same density. Increasing density of alligator weed caused more losses in paddy yield (up to 21.37–23.78%), amylose and rice grain protein contents. According to a nonlinear hyperbolic regression model, maximum paddy yield loss of rice at asymptotic value of alligator weed density was 38.8% during 2011 and 42.4% during 2012. Economic threshold value of alligator weed was estimated 1.5 and 1.3 plants per m² during 2011 and 2012, respectively.     

An Observational Method for the Assessment of Biogas Production from an Anaerobic Waste Stabilisation Pond treating Farm Dairy Wastewater

A biogas production assessment method based on the visual monitoring of biogas evolution events in an anaerobic waste stabilisation pond was developed and applied to an anaerobic pond treating farm dairy wastewater in New Zealand. Major biogas-induced perturbations at the pond surface were classified as either type 1 or 2 events and other observed biogas activities as small bubble events. Mean counts of types 1 and 2 events varied from 7·3 to 30·0 per hour and 4·3–34·0 per hour, respectively, over the pond surface and the frequency of events decreased as both organic loading and temperature increased. Preliminary estimates of areal gas production rates, obtained using the observational method, ranged from 0·002 to 0·015 m³ m⁻² day⁻¹ for major eruptions and 0·0004–0·024 m³ m⁻² day⁻¹ for small bubble events, giving a total range of 0·002–0·039 m³ m⁻² day⁻¹. Pond temperatures at 2·75 m depth showed relatively minor fluctuations on a diurnal basis and ranged between 13 and 15°C from days 1–60, reaching a maximum of 24°C at day 190. Refinements proposed for future method development include an increased number and range of event categories, the automatic recording of events and the use of an improved cover. Further work is required to assess the general applicability of the method to anaerobic ponds.     

The distribution of volatile isoprenoids in the soil horizons around Pinus halepensis trees

We measured the terpene concentration in pentane and water extracts from soil horizons (litter, organic, top and low mineral) and from roots growing in top and low mineral horizons on a distance gradient from Pinus halepensis L. trees growing alone on a grassland. Terpene concentrations in pentane were higher than in water extracts, although β-caryophyllene showed relatively high solubility in water. The litter and roots were important sources of terpenes in soil. Alpha-pinene dominated in roots growing in both “top” (A1) and “low” (B) mineral horizons (123 ± 36 μg g⁻¹ or 14 ± 5 mg m⁻²) and roots in low mineral horizon (270 ± 91 μg g⁻¹ or 7 ± 2 mg m⁻²). Beta-caryophyllene dominated in litter (1469 ± 331 μg g⁻¹ or 2004 ± 481 mg m⁻²). Terpene concentration in soil decreased with increasing distance to the trunk. This is likely to be related to changes in litter and roots type on the distance gradient from pine to grass and herbs. The relative contributions of all compounds, except α-pinene, were similar in the mineral soils and litter. This suggests that litter of P. halepensis is probably the main source of major terpene compounds. However, long-term emissions of α-pinene from P. halepensis roots might also contribute to α-pinene concentrations in rhizosphere soils.     

Effect of Changing Temperature on the Deterioration of Soya Beans

Deterioration rates as indicated by carbon dioxide evolution for soya bean (Glycine max L. Merr.) stored under changing temperature conditions were quantified and compared with those predicted using equations. Experiments included soya bean moisture contents of 18, 22, and 26% (wet basis), constant storage temperatures of 15, 20, 25, and 30°C, and cyclical storage temperatures that changed between 15 and 25°C and between 20 and 30°C on a 24 h basis. Also, the growth of micro-organisms was identified after 10 days from the treatments by using the pour plate method.The results indicated an increase in deterioration by increasing storage temperature and moisture content of soya bean. Equations of carbon dioxide weight versus time for each moisture content and storage temperature were fitted. The longest allowable storage time to reach 0·5% dry matter loss (1132 h) occurred at lower moisture content and lower constant storage temperature, while the shortest allowable storage time (170 h) occurred at higher moisture content and higher constant storage temperature. The allowable storage times for soya bean stored under cyclical temperatures were close to the allowable storage time for soya bean stored at a constant temperature equal to the average cyclical temperature. Microbial infection levels increased with increasing storage temperature and moisture content. The increasing rate of micro-organism growth decreased by increasing the storage temperature over 25°C. However, this increasing rate of micro-organism growth for soya bean exposed to a cyclical storage temperature was usually lower than that for soya bean held at constant storage temperatures of about 20°C (the average of 15 and 25°C) and 25°C (the average of 20 and 30°C).     

Cesium and soil carbon in a small agricultural watershed

Scientific, political, and social interests have developed recently in the concept of using agricultural soils to sequester carbon. Studies supporting this concept indicate that soil erosion and subsequent redeposition of eroded soils in the same field may establish an ecosystem disequilibrium that promotes the buildup of carbon on agricultural landscapes. The problem is to determine the patterns of soil erosion and redeposition on the landscape and to relate these to soil carbon patterns. Radioactive ¹³⁷cesium (¹³⁷Cs) can be used to estimate soil erosion patterns and, more importantly, redeposition patterns at the field level. The purpose of this study was to determine the relationship between ¹³⁷Cs, soil erosion, and soil carbon patterns on a small agricultural watershed. Profiles of soils from an upland area and soils in an adjacent riparian system were collected in 5 cm increments and the concentrations of ¹³⁷Cs and carbon were determined. ¹³⁷Cs and carbon were uniformly mixed in the upper 15–20 cm of upland soils. ¹³⁷Cs (Bq g⁻¹) and carbon (%) in the upland soils were significantly correlated (r²=0.66). Carbon content of the 0–20 cm layer was higher (1.4±0.3%) in areas of soil deposition than carbon content (1.1±0.3%) in areas of soil erosion as determined by the ¹³⁷Cs technique. These data suggest that measurements of ¹³⁷Cs in the soils can be useful for understanding carbon distribution patterns in surface soil. Carbon content of the upland soils ranged from 0.5 to 1.9% with an average of 1.2±0.4% in the 0–20 cm layer while carbon below this upper tilled layer (20–30 cm) ranged from 0.2 to 1.5% with an average of 0.5±0.3%. Total carbon was 2.66 and 3.20 kg m⁻² in the upper 20 cm and upper 30 cm of the upland soils, respectively. Carbon content of the 0–20 cm layer in the riparian system ranged from 1.1 to 67.0% with an average 11.7±17.1%. Carbon content below 20 cm ranged from 1.8 to 79.3% with an average of 18.3±17.5%. Soil carbon in the upper 20 cm of the riparian profile was 10.1 and 15.0 kg m⁻² in the upper 30 cm of the riparian profiles. This is an increase of organic carbon by a factor of 3.8 and 4.7 for the upper 20 cm and upper 30 cm of the riparian profiles, respectively, when compared to the upland soil profiles.     

Mechanical Behaviour of Hazelnut under Compression Loading

Aci Findik, Cakildak, Tombul, and Güney Karasi varieties of hazelnut were loaded between two parallel plates to determine the specific deformation, rupture force, and rupture energy required to initiate shell and kernel rupture. The tests were carried out at two deformation rates of 0·52, and 0·91 mm s⁻¹, four moisture contents of 6, 11, 15, and 18% w.b., and three axes (X,Y,Z). The X-axis is the longitudinal axis through the hilum, while the Y-axis is the transverse axis containing the major dimension at right angles to the longitudinal axis, and the Z-axis is the transverse axis containing the minimum dimension. Physical characteristics of nut and kernel such as mass, dimensions, geometric mean diameter and sphericity were determined. Specific deformation and rupture energy of the shell generally increased in magnitude with an increase in moisture content while rupture force decreased for compression along the X- and Y-axis. The highest nut shell specific deformation, rupture force and rupture energy among the four varieties were obtained for Aci Findik nuts loaded along the Z-axis at a deformation rate of 0·52 mm s⁻¹. The Tombul and Güney Karasi varieties had the highest kernel rupture force and rupture energy, respectively.     

Sorption Isotherms of Tomato Slices and Onion Shreds

Experiments were conducted to determine the equilibrium moisture content of tomato (cv Roma) slices and white onion shreds at temperatures of 30, 40 and 50°C and relative humidities of 15–85% obtained from an air conditioning unit. The samples were placed on trays and the equilibrium moisture contents were determined once the samples attained the constant mass. The equilibrium moisture content–equilibrium relative humidity data were fitted to the modified Henderson, Chung-Pfost, modified Halsey, modified Oswin, and modified GAB models. The modified Henderson and modified Halsey models fitted well for the tomato slices and onion shreds, respectively, based on the coefficient of regression, mean relative percent error and standard error of moisture. The values of these parameters were, 0·985, 2·58 and 0·52, respectively, for the modified Henderson model for the sliced tomatoes and 0·991, 2·01 and 0·42, respectively, for the modified Halsey model for onion shreds.     

太湖地区水稻土的物理特性与少免耕法的关系

本文从土壤物理特性和作物生长的关系探讨了耕作的要求.土壤水分能量特性可被机械扰动改变,这是导致土壤粘闭的重要原因.水稻土的含水量和有效水均以表土高,而下层低,含水量和容重成线性负相关(n=62,r=-0.909^**).土壤扰动可提高持水量,长年免耕在干旱年份可能会出现水分不足问题.土壤含水量、气容量和机械强度三者的变化相互联系.由三个因素决定的小麦生长最佳范围是在水分吸力0.02-0.5巴内,而田间持水量大于塑性限,所以秋季耕作必然导致土壤粘闭.免耕土壤的容重一般在1-1.25g/cm₃之间,是稻麦生长的较佳环境,所以水稻土本身存在适合稻麦免耕生产的条件.根据水稻和三麦分别52和23组次对比试验,水稻免耕增产19斤/亩,三麦49斤/亩,均达到极显著水平(p=0.01).平田地区连续三年免耕土壤不恶化,囊水型土壤第二年开始有变差趋势,但产量不减低.免耕有保护土壤结构的作用,但不利于结构发展.