Nitrogen and phosphorus management under long-term experiments

The investigations conducted at the Podu-Iloaiei Agricultural Research Station, Iaşi County, Romania, have studied the influence of different mineral fertilizers rates on wheat and maize yield and soil agrochemical characteristics. In bean-wheatmaize- sunflower-wheat crop rotation, the mean yield increases, obtained for each kg of a.i. of applied fertilizer, were comprised between 8.3 and 10.1 kg in wheat (N120P80- N160P80) and between 10.8 and 11.0 kg in maize (N150P80-N200P100). Generally, nitrogen use efficiency is low and, to achieve maximum yields, need for high doses of nitrogen which can increase the risk of environmental pollution. The N agronomic efficiencies and physiological efficiencies in wheat and maize declined with the increase of nitrogen rate. Wheat placed in rotation for five years, after sunflower at recommended dose (N160P80), physiological efficiency of nitrogen utilization was 43.4 kg grain per kilogram of nitrogen exported from soil, from fertilizer applied. Mean annual amounts of nutrients exported from soil by wheat in dry (14 yr.) and favourable (11 yr.) years in five year crop rotation have varied according to rates, between 34.5 and 100.7 kg at nitrogen and between 6.5 and 18.4 kg at phosphorus. The long-term use of bean - wheat - maize - sunflower - wheat rotation determined the diminution by 43.4% (2,772 t/ha) in the mean annual losses of eroded soil and by 38.5% (5.61 kg/ha) in nitrogen leakages by erosion, compared with maize continuous cropping

Soil erosion and conservation measures in Moldavian Plateau

The long-term experiments carried out at the Agricultural Research Station of Podu-Iloaiei, Iaşi County, Romania, tried to establish some fertilization systems for getting efficient yield increases, which maintain or increase the content of organic carbon from soil. These trials were set up on a 16% slope field, with a cambic Chernozem soil, which has a clayey-loam texture, a neuter to weakly acid response and a mean supply in nutrients. Analyzes performed on soil profiles after 44 years, on land with a slope of 16% and slope length of 310 m, shows that the entire length of slope soil fertility were very different, being influenced by processes of erosion and silting. Soil organic carbon, the depth of 0-20 cm, was between 45.94 t / ha, the foot slope and 27.45 t / ha in the mid-slope area with strong erosion. From the results obtained on erosion in different crop rotations, we have found out that in 16% slope fields from the Moldavian Plateau, soil losses by erosion were diminished below the allowable limit of 3-4 t/ha/year only in case of 4 year-crop rotations with two reserve fields, cultivated with legumes and perennial grasses, which protect soil. Annual soil losses by erosion, registered during the last 30 years, in the Moldavian Plateau, were between 0.246 t/ha in perennial grasses, on the second year of vegetation, and 8.976 t/ha in sunflower. The fertilization of wheat and maize crops at the rate of N80P80 + 60 t/ha manure has determined the increase with 5.5 t/ha (7.8%) in the content of organic carbon from soil, as compared to the rate of N140P100

Long-term effect of fertilizer and crop residue on soil fertility in the Moldavian plateau

Since 1965, at the Agricultural Research Station of Podu- Iloaiei, Iaşi County, Romania (47°12´ N latitude, 27°16´ E longitude), investigations were conducted on the influence of different fertilizer systems on production and soil fertility. For wheat and maize crops, placed in a three-year rotation (pea - wheat - maize), three fertilization systems were experienced: (1) mineral fertilization with nitrogen and phosphorus rates until N140P100; (2) manure fertilization (20, 40, and 60 t/ha), with and without mineral fertilization and (3) mineral fertilizers + hashed residue applied in autumn under the base ploughing. The paper presented the results of investigations concerning the influence of long-term fertilization (46 years) on some chemical characteristics of Cambic Chernozem from the Moldavian Plateau. The climatic conditions in the Moldavian Plain were characterized by annual mean temperature of 9.6oC and a mean rainfall amount, on 50 years, of 553.5 mm, of which 141.5 mm during September-December and 412.0 mm during January-August. After 46 years of experiences, in pea-wheat-maize crop rotation, the content of organic carbon from soil has decreased by 22.3% (4.2 g/kg soil) at the unfertilized control and by 14.4% (2.7 g/kg soil) at the rate of N120P80. In wheat and maize, nitrogen uptake by weeds was between 7 and 9.5 kg/ha from all the plots. Applying moderate rates of mineral fertilizers (N80P60), together with 6 t/ha wheat straw or 40 t/ha manure, has determined the increase in organic carbon content from soil by 0.5 and, respectively, 2.8 g/kg

Critical season for soil erosion in the Moldavian plateau

Experiments conducted at Agricultural Research and Development Station of Podu-Iloaiei, Iaşi County, Romania, during 2002 - 2011, followed study runoff and soil erosion in different cultures, and establish critical season of soil erosion in this area. Establish critical season of soil erosion is necessary to satisfy the critical level of ground cover, which is required to maintain a low risk of soil erosion. Average annual soil loss by erosion, recorded in maize and sunflower were (mean on 10 years) of 6.753 and 7.385 t/ha/year, respectively. In sunflower and corn of the total soil loss recorded in the Moldavian Plateau, 19.7- 20.4% occurred in spring, 68.7 to 69.2% in summer and 6.1- 6.6% in the autumn. Differences of 4.5 to 4.9% of the total annual soil losses by erosion were recorded in winter, with snow melt. Season critic of soil erosion in the Moldavian Plateau, when recording the most aggressive rain event occurs in June and July. Mean soil loss due to erosion, recorded in June and July were 0.424 t/ha for winter rape, winter wheat 0.291 and 0.093 t/ha the perennial grasses in the second year of vegetation

ASPECTS REGARDING THE ENERGETICALLY EFFICIENCY OF IRRIGATION OF SOME CROPS IN NORTH-EAST ROMANIA

On the basis of some registered information in three areas from Moldova, it was calculated the energy balance and the energetically efficiency of the applied irrigation on eight species of plants. The information's obtained proved that the irrigation process is efficient from the energetically point of view for all the field crops which have been seen in south droughty zone and this process is less efficient in central and moderate warm and moist zone. In the cool moist zone from northern, the irrigation process is efficient only in a few cultures. On the slope lands, where the cultures need more water, the energetically efficiency of the irrigation process is greater than on a plat field. The greatest values of the balance and energetically efficiency were obtained in sugar beet, followed by alfalfa, maize for grain or silage, potato, wheat and sunflower, on the last places coming soybean and bean. There reacted favourable to irrigation the sugar beet, followed by maize for grain or silage, sunflower, potato and wheat, in bean and soybean being registered an energy balance very reduced

The evolution of chemical and biological characteristics in Cambic Chernozem, under the influence of crop rotation, fertilizers and soil erosion

Investigations conducted at the Agricultural Research and Development Station of Podu-Iloaiei, Iaşi County, during 2004-2008, have followed the influence of different crop structures and different fertilization methods on crop yield, erosion and soil fertility. Within the experiment, the following rotation schemes have been followed: wheat and maize continuous cropping, 2-year rotation (wheat-maize), 3-year rotation (peas-wheat-maize) and 4-year rotation + reserve field cultivated with legumes and perennial grasses (alfalfa + Lolium or Sainfoin + Bromus). The use of 3 and 4 year- rotations with annual and perennial meliorate plants has resulted in yield increases of 25 – 30 % (632 – 768 kg/ha) in wheat and 24-28% (973-1161 kg/ha) in maize, as compared to continuous cropping. The fertilization of wheat and maize crops at the rate of N60P40+30 t/ha manure has determined the increase by 3.0 g/kg (17.9%) in the content of organic carbon from soil, as compared to the rate of N100P80. The use of peas-wheat-maize-sunflower rotation + reserve field grown with legumes and perennial grasses has contributed to the increase by 2.2 g/kg (13.4%) in the content of organic carbon. The use of 4-year rotation + reserve field cultivated with perennial grasses and legumes on slope lands, poor in organic matter has determined the increase by 47% in soil potential and by 34% in enzyme potential, as compared to wheat-maize rotation. On 11% slope lands, the use of soybean-wheat-maize rotation + two reserve fields cultivated with perennial grasses has determined the diminution of soil losses by erosion at 0.985 t/ha, and on 16% slope lands, peas-wheat-maize rotation + two reserve fields, cultivated with perennial grasses has determined the diminution in soil erosion at 1.371 t/ha. On 16% slope lands, the crop structure, which determined the diminution in mean soil losses by erosion until 1.371 t/ha/year included 20 % straw cereals, 20% annual legumes, 20% row crops and 40 % perennial grasses and legumes

Evolution of some chemical properties of soil under influence of soil erosion and different cropping systems

Since 1968, at the Agricultural Research Station of Podu- Iloaiei, Iași County (47°12´ N latitude, 27°16´ E longitude), investigations were conducted on the influence of different crop structures and fertilizers on yield, erosion and soil fertility. The paper presented the results of investigations concerning the influence of long-term fertilization (43 years) on some chemical characteristics of Cambic Chernozem from the Moldavian Plain and on the yield of wheat and maize, placed under different crop rotations with perennial grasses and legumes. The objectives of this study was, to monitor runoff, soil loss and soil chemical properties in monocultures of wheat and corn, compared with different rotations and fallow land. The climatic conditions in the Moldavian Plain were characterized by annual mean temperature of 9.6oC and a mean rainfall amount, on 50 years, of 553.5 mm, of which 141.5 mm during September- December and 412.0 mm during January- August. In the last 20 years, the mean annual recorded quantity of rainfall was of 588.7 mm (100%), of which 369.5 mm (62.8%) determined water runoff and soil losses by erosion. Mean annual losses of soil by erosion, recorded in the last 20 years, in the Moldavian Plain, were of 0.161 t/ha in perennial grasses in the second growth year, 3.883 t/ha in beans, 6.369 t/ha in maize and 6.733 t/ha in sunflower. The crop structure, which determined, during 1991- 2010, the diminution in mean soil losses by erosion until 1.954 t/ha/year included 20 % straw cereals (wheat), 20% annual legumes (pea), 20% row crops (maize) and 40 % perennial grasses and legumes (Alfalfa + Lolium perene). After 43 years of experience, in the pea - wheat - corn - sunflower rotation + reserve field, cultivated with legumes and perennial grasses, soil organic carbon content increased with 14.7% (2.8 C g / kg), in comparison with wheat - maize rotation

Effects of long-term fertilization on the fertility of erosion-affected soils from the Moldavian Plateau

The paper presented the results of investigations concerning the influence of long-term fertilization (43 years) on some chemical characteristics of Cambic Chernozem from the Moldavian Plain and on the maize yield. On slope lands, the high rate fertilization of maize crop (N140P100) has determined, in the latest ten years, an average yield increase of 103% (3373 kg/ha), against the control, and applying a rate of N70P70+40 t/ha manure resulted in getting a very close yield increase (99%, 3258 kg/ha). The minimum supply level of mobile phosphorus in soil (37-72 ppm) in pea-wheat-maize rotation (37 ppm) was maintained in case of annual application of a rate of N100P80. The total carbon content in Cambic Chernozem from the Moldavian Plain has registered significant increases at higher rates than N140P100 and in case of organo-mineral fertilization. The annual fertilization of wheat and maize, at the rate of 70 kg N + 70 kg P2O5/ha + 6 t/ha stalks of wheat, has determined, compared to the unfertilized variant, the increase in the content of organic carbon from soil by 14.5% (2.4 g organic C/kg) on weakly eroded soils, and by 29.5% (4.2 g organic C/kg) on highly eroded soils. During the long-term fertilizing of wheat and maize with high rates of mineral fertilizers (N140P100), on highly eroded lands, the total content of carbon has increased by 16.9% (2.4 g organic C/kg soil), against the unfertilized control. Applying moderate rates of mineral fertilizers (N70P70), together with 60 t/ha manure, has determined, after 43 years of testing, the increase by 32% (5.3 g organic C/kg) in the content of organic carbon from soil, on weakly eroded soils, and by 42.3% (6.0 g organic C/kg soil) on highly eroded soils, compared to the unfertilized control. On 16% slope arable lands from the Moldavian Plateau, the mean annual soil losses by erosion, registered during 1986-2007, were of 1.640 t/ha in winter wheat, 4.618 t/ha in beans, 1.89 t/ha in the field cultivated with perennial grasses and legumes on the second year of vegetation, 9.176 t/ha in maize and 9.6 t/ha in sunflower

Effect of municipal sewage sludge on winter rape and soybean production and heavy metal contamination of soil

Investigations conducted during 2004-2008 at the Podu-Iloaiei Agricultural Research Station have studied the influence of different rates of sewage sludge on yield and soil agrochemical characteristics. Sewage sludge was applied annually at rates of 20, 40 and 60 t/ha, together with mineral fertilizers, differentiated according to the growing plant. Applying rates of 20 t/ha DM sewage sludge resulted in the accumulation of mobile phosphate stock in soil of 58 ppm; the microelement content (mobile forms from soil) was of 19.0 ppm at Cu, 0.51 ppm at B, 149 ppm at Zn and 397 ppm at manganese. The obtained results have shown that by applying a rate of 30 t/ha of raw sewage sludge (18.5 l t/ha dry matter), the allowable maximum limits stipulated by Norm 86/278/EEC, were not exceeded. By applying rates of 60 t/ha raw sewage sludge (37 t/ha dry matter), the limits established by Norm 86/278/EEC and Order no. 49 from January 14, 2004 have been exceeded only at zinc. The application of the rates of 40 t/ha sewage sludge has resulted in increasing the degree of plant supply by mineral elements (especially, nitrogen and phosphorus). It has also resulted in a mean annual supply of 3.8 t/ha highly humificated organic matter; this explains the increase in soil humus content (after 4 years) from 2.82 to 3.79%. The use of fermented sewage sludge, at a rate of 40 t/ha, has resulted in getting mean yield increases of 65 % (1075 kg/ha), in winter rape, and of 63 % (937 kg/ha), in soybean. For slope lands degraded by erosion, sewage sludge with other organic resources may contribute to the improvement in soil characteristics. The application of rates of 20 t/ha sewage sludge DM has resulted in the accumulation of mobile phosphates in soil of 58 ppm, and the content of microelements, mobile forms from soil, was of 19.0 ppm at Cu , 0.51 ppm at B, 149 ppm at Zn and 397 ppm at manganese

Influence of different organic resources on crop yield and soil fertility in the Moldavian Plateau

Investigations conducted during 2003-2007 at the Podu-Iloaiei Agricultural Research Station have studied the influence of different sewage sludge, manure and crop residues on yield quality and quantity and soil agrochemical characteristics. Experiments were set up in a five year-crop rotation (soybean-wheat-maize-sunflower-wheat). Sewage sludge was applied annually at rates of 20, 40 and 60 t/ha, together with mineral fertilizer, differentiated according to the growing plant. The Cambic Chernozem used for experiments had a clayey-loam texture (415 g clay, 305 g loam and 280 g sand), a weakly acid reaction and a mean supply with mobile phosphorus and a very good one with mobile potassium. Applying rates of 24.6 t/ha DM sewage sludge resulted in the accumulation of mobile phosphate stock in soil of 49 ppm and the microelements content (mobile forms from soil) was of 12.4 ppm at Cu, 0.47 ppm at B, 142 ppm at Zn and 382 ppm at manganese. The combined use of mean rates of mineral fertilizers (N70P70), together with 40 t/ha manure or 6 t/ha crop residues from wheat and maize crops, has resulted in improving soil physical and chemical characteristics and getting yield increases in wheat of 2313-2214 kg/ha (136-130 %), on weakly eroded lands, and 2074-2001 kg/ha (178-172 %) on highly eroded lands, compared to the unfertilized control. Both on weakly and highly eroded lands, the mineral fertilization with lower rates than N140P100 kg/ha has determined the decrease in humus content from soil until 2.49- 3.05 %. On highly eroded lands, the humus content was kept at values of 3.42-3.49% only by the annual application of the rate of 60 t/ha manure or N70P70+ 60 t/ha manure