Is it economically feasible to harvest by management zone?

The economics of harvesting wheat based on input management zones in the northern wheatbelt of Western Australia was studied using a simulated field of regular dimensions with varying zone sizes and layouts. Fertilizer application rates and crop yield and quality data from field trials of input management were used to estimate the gross crop revenue and harvesting costs from the different field layouts and zone combinations. As a general observation there was no consistency in the results; harvesting by zone generated more gross income in some combinations of field layout and yield quantity scenarios, but not in others. However, there were key factors in determining whether it was profitable to harvest by zone. These were prior knowledge of the potential yield and quality characteristics of grain from each zone in a field, and the layout of zones within a field.     

25%高氯·辛微乳剂防治棉铃虫、菜青虫试验

田间试验结果表明 ,2 5%高氯·辛微乳剂对棉铃虫和菜青虫具有较好的防治效果。用 10 0 0～ 150 0倍液防治棉铃虫 ,药后 5d防效和保蕾效果分别达 79%和 74 %以上 ;用 10 0 0～ 2 0 0 0倍液防治菜青虫 ,药后 7d防效达 94 %以上。与氯氰菊酯和高效氯氰菊酯的防效相当 ,优于常规农药辛硫磷。     

施肥对白背飞虱田间种群和水稻产量的影响研究

本文分析了氮、磷、钾化肥及农家肥对白背飞虱田间种群和水稻产量的影响.结果表明:氮素化肥是影响白背飞虱田间种群数量变动的主导因素,磷肥对白背飞虱的发生亦有一定的推动作用,农家肥和钾肥对白背飞虱有微弱的抑制作用.多施氮素化肥,即使配合施用较多的其它肥料,也不能减少田间虫口密度.较多的农家肥配合少量的氮素化肥,既可以减少白背飞虱田间发生量,又有利于提高水稻产量.     

韭菜迟眼蕈蚊幼虫田间分布型及抽样技术研究初报

以聚集指标及Iwao回归、Talor回归确定韭菜田韭菜迟眼蕈蚊幼虫的田间分布状态。结果表明,韭菜田韭菜迟眼蕈蚊幼虫呈聚集分布,服从负二项分布型,幼虫的聚集是由生物习性造成的。u统计量分析表明,韭菜田较为理想的抽样方式有Z字形、棋盘式和平行线法。10点、12点、14点抽样数据的离散度小,8点抽样误差大。     

远离城镇小尺度的农田土地利用变化分析——以北涝沟村为例

参照参与性农村评估法,对北涝沟村进行了多次实地考察,获取了可靠的土地利用变化的研究资料,应用转移矩阵和生态分析等研究方法对远离城镇的北涝沟村的土地利用变化及未来趋势和生态价值做了分析。结果表明:水田已经成为该村主要的土地利用类型,由旱地向水田的转化是其土地利用变化的主要特点。土地利用结构的变化提高了生态系统的服务功能和价值,并继续向着良好的方向发展。这为远离城镇小尺度的农田土地利用以及生态变化的人为调控和建设提供科学依据。     

田间枣树叶片复杂目标图像综合分割方法

设计了一种复杂图像分割的综合算法。首先对图像进行预处理,锁定大致目标范围,对图像进行增强,再基于阈值分割和Canny算子对图像进行初步分割。然后结合形态学处理方法及各种逻辑运算对分割结果进行优化处理,得到精确完整的目标图像。以田间枣树叶片图像为例进行实验,证明了该算法的可行性和有效性。该算法对叶片重叠、叶片灰度不均匀等复杂图像都有很好的分割效果,获得了边缘清晰、平滑、定位精确的边缘图像。     

The contribution of rock fragments to the available water content of stony soils: Proposition of new pedotransfer functions

The contribution of rock fragments to the soil available water content (SAWC) of stony soil has been quantified by measurements of bulk density and gravimetric water content at different water potentials on rock fragments of different lithologies: flints, cherts, chalks, gaizes and limestones. More than 1000 pebbles (2 cm < equivalent diameter of the rock fragment < 5 cm) have been sampled in stony soils developed from each of the five lithologies. We demonstrated that the water content at saturation of the studied pebbles was equal to the water content at −100 hPa and to the water content at field capacity. A linear relationship between the water content at −100 hPa and at −15,840 hPa enabled to derive a simple pedotransfer function to determine the available water content of the rock fragments. We also proposed a second simple pedotransfer function, which expresses the available water content from the dry bulk density of the rock fragments only. A simulation at the horizon scale for a loamy-clay stony horizon showed that the SAWC could be strongly misjudged when the rock fragments were not taken into account: for a stony horizon containing 30% of pebbles, the SAWC is underestimated by 5% for chert pebbles and by 33% for chalk pebbles.     

Measured and simulated denitrification activity in a cropped sandy and loamy soil

Summary Denitrification activities were measured over a 3-year period in a coarse sandy soil and a sandy loam soil. In all years the crops were spring barley in combination with Italian ryegrass as a catch crop. The denitrification loss was measured using the acetylene inhibition technique on soil cores. Furthermore, a simple model was developed, based on daily values of soil moisture and soil temperature, to calculate the denitrification loss. Soil temperatures for the model were measured, whereas soil moisture was derived from a water-balance model. Measurements of denitrification gave an annual loss of 0.6 kg N ha^-1, and the model calculated a loss of 1–2 kg N ha^-1 in the coarse sandy soil. In the sandy loam soil annual losses were measured as 1.5, 3.0, and 13.0 kg N ha^-1 in 1988, 1989, and 1990, respectively. The corresponding values from the model simulation were 14, 9 and 14 kg N ha^-1.     

What happens to earthworm casts in the soil? A field study of carbon and nitrogen dynamics in Neotropical savannahs

In the Oxisols of the eastern plains of Colombia, the large native anecic earthworm Martiodrilus sp. is an abundant ecosystem engineer producing long-lasting casts and burrows. Casts deposited in the soil by this species have been estimated at several tonnes per hectare per year. The physical and chemical processes occurring in these casts have never been studied. In this study, we compared the dynamics of water content (WC), total C (C_tot), and available N (N_avail) contents, and the distribution in size of aggregates in ageing below-ground casts of this species and in the bulk soil. In a native herbaceous savannah and a sown grass/legume pasture (Brachiaria humidicola, Arachis pintoi, Desmodium ovalifolium and Stylosanthes capitata), fresh surface casts were experimentally injected into artificial burrows of 1 cm Ø and 10 cm depth and sampled at different dates during a total period of 120 days. The injection procedure used resulted in a 34% decrease in WC of the casts from the sown pasture and reduced the mean mass diameter (MMD) of the aggregates of casts from the savannah by 19%. Other properties were not significantly affected by the procedure.For injected casts in both grasslands, MMD and C_tot were stable during cast ageing while WC and N_avail were initially at levels several times higher than the bulk soil and decreased to similar bulk soil values with ageing. The C_tot was twice and one third higher in casts compared with the bulk soil in the pasture and the savannah, respectively. Overall means for cast MMD (8.3 and 7.4 mm) were twice as high as those in the bulk soil (3.8 mm) in the savannah and the pasture, respectively. However, MMD was not significantly different between the casts and the bulk soil in two occasions in the pasture. Available nitrogen (N_avail) in injected casts was initially greater than bulk soil levels, reaching maximum levels just after injection (116 and 93 mg kg⁻¹) and remained significantly greater during 1-2 weeks, in the savannah and the pasture, respectively. In conclusion, the tonnes of casts deposited in the soil profile by Martiodrilus sp. each year are likely to contribute greatly to plant nutrition and to the regulation of the soil structure. For each anecic earthworm species, the ecological impact of its below-ground casts is likely to be as important as its surface casts.     

太湖地区稻麦轮作农田氮素淋洗特点

通过排水采集器模拟试验研究了太湖地区不同施肥水平下农田N素淋洗特点。结果表明,N的渗漏损失以硝态氮（NO3^--N）为主,并发生在麦季,铵态氮（NH4^ -N)淋洗量则很少,NO3^--N的量占渗漏液总N量的43%-72%,浓度为20-110mg/kg;渗漏水中N的含量与土壤N的淋洗量随施肥量的增加而增加,麦季土壤中NO3^--N肥量的3.7%-12.2%;与纯化肥处理比较,化肥 猪粪处理增加了农田N的淋失,化肥 秸秆处理减少了土壤中N的淋失,与麦田渗漏水相比较,稻田渗漏水除水稻生长早期的部分样品外,NO3^--N和NH4^ -N含量均很低,分别在1mg/kg和0.5mg/kg以下。