THE EFFECT OF FORECROP GREEN FERTILIZERS ON THE YIELDING AND GROWTH OF SUGAR MAIZE ‘LANDMARK F₁’

Romualda Jabłońska-Ceglarek, Robert Rosa
Department of Vegetable Crops, Podlasie University in Siedlce, Poland

ABSTRACT

The effect of green fertilizers in the form of forecrops was studied on the yielding and growth of sugar maize ‘Landmark F₁’. The maize was cultivated directly after organic fertilization. The plants intended for green fertilizer were sown in the first 10 days of April, and they were ploughed over in the first 10 days of June. The yielding of sugar maize was related to the course of the weather conditions in particular years of the experiment. Its highest yields were obtained in 2002. Application of organic fertilization caused an increase of maize yields as compared to the cultivation without organic fertilization. It yielded the best after field pea, a mixture of vetch with field pea and after manure. The weather conditions in particular years of the studies had a significant effect on the height of sugar maize plants, the number of cobs on 1 plant, the length, diameter and mass of the cobs. The highest plants grew after manure, the mixture of vetch with field pea and after field pea. The greatest number of cobs on 1 plant was found in the cultivation of maize after field pea. The cobs collected from the maize cultivated on the ploughed after-crop residues were significantly longer than those collected from the maize grown after ploughing in the green fertilizers as the whole. The longest cobs were observed in the cultivation of maize after ploughing in the field pea. The biggest diameter of cobs was characteristic of the maize grown after ploughing in the green fertilizer from field pea. The greatest mass was found for the cobs collected from the maize cultivated after vetch. The biggest mean mass of grains themselves was characteristic of the cobs from the plants grown on the plots with the ploughed in green fertilizer from field pea.

Key words: organic fertilization, green fertilizers, forecrop, sugar maize, yield.

INTRODUCTION

Interest in the cultivation of sugar maize in Poland has increased year after year. At present it is grown in Poland in the area of about 3,000 ha. The soil-climatic conditions of Poland favour its cultivation and the profitability of production is very high [25, 22].

A great influence on the yielding on sugar maize is exerted by the weather course, especially the air temperature in the period of vegetation [14, 18]. The success of the cultivation is also determined by agrotechnological factors, among which a significant role is played by fertilization. The choice of the proper stand and soil, which should be rich in humus, permeable and which should get warm fast is also of importance. The advancing processes of mineralization cause constant decrease of the amount of humus in the soil. In order to prevent it and keep the soil in the proper culture, it is necessary to introduce the organic matter into it systematically. Green fertilizers are an easily accessible source of it [4, 7]. According to Debruck [6] and Franczuk [8], in the situation of a shortage of manure fertilization with straw and green fertilizers can maintain the level of humus in the soil. The effect of green fertilizers depends to a large extent on the mass of the ploughed in plants, the rate of their mineralization as well as on the climatic conditions – mainly the size and distribution of atmospheric rainfalls [2, 3]. The advantages of using green fertilizers include considerable reduction of production costs [10] and saturation of rotations with catch crops, which is so important in ecological agriculture [17].

The purpose of the present paper was to establish the effect of green fertilizers sown and ploughed in in spring on the yielding and growth of sugar maize.

METHODS

The field experiment was conducted in the conditions of central-eastern Poland in the years 2002-2004. The experiment was set on a stand after rye, on the brown soil proper formed from light loamy sands. The humus level in the soil reached the depth of 30-40 cm. The content of organic carbon was 0.9%, on average. The soil’s reaction was acidic – pH in H₂O 5.6. The experiment was set as split-block in four repetitions. It studied the consecutive effect of green fertilizers in the form of forecrop plants on the yielding and growth of sugar maize ‘Landmark F₁’. The following were cultivated for green manure: oat (the sowing norm of seeds 240 kg·ha^-1, field pea (160 kg·ha^-1), spring vetch (140 kg·ha^-1) and the mixtures of oat (100 kg·ha^-1) with field pea (130 kg·ha^-1), spring vetch (10 kg·ha^-1) with oat (80 kg·ha^-1), spring vetch (50 kg·ha^-1) with field pea (70 kg·ha^-1), spring vetch (50 kg·ha^-1) with field pea (70 kg·ha^-1) and oat (100 kg·ha^-1). The area of the plot was 16 m².

Mineral fertilization was applied before sowing the plants intended as green fertilizer. The dose of phosphorus and potassium under all forecrop plants was 80 kg P₂O₅·ha^-1 and 160 kg K₂O·ha^-1. Nitrogen fertilization was differentiated: for field pea and spring vetch in pure sowing and for the mixture of vetch with field pea it was 30 kg N·ha^-1, for oat in pure sowing 90 kg N·ha^-1, for the mixtures of oat with field pea and spring vetch with oat it was 60 kg N·ha^-1, while for the mixture of spring vetch with field pea and oat it was 40 kg N·ha^-1. The forecrops were sown during the first 10 days of April, and they were ploughed in at the turn of May and June. Two forms of using them as green fertilizer were applied – the whole biomass of plants and aftercrop residues. Immediately before the plants intended as green fertilizer were ploughed in, samples were taken from the area of 1 m² in order to determine the aboveground mass of plants and the mass of crop residues, which was made up of the roots with a 5-cm deep layer of stubble. Besides, chemical analyses were made with the aim of establishing the level of nitrogen.

The effect of green fertilizers was compared with the effect of manure in the dose of 25 t·ha^-1 and the control object without organic fertilization.

Sugar maize ‘Landmark F₁’ was cultivated directly after organic fertilization. The seeds were sown during the first 10 days of June at the spacing of 75×20 cm. Before that, mineral fertilization had been performed on all plots in the quantity of 110 kg N, 110 kg P₂O₅, 170 kg K₂O per 1 ha. Mineral fertilizers under the forecrops and maize were used in the form of ammonium saltpeter, granular superphosphate and 60% potassium salt. The other treatments were in accordance with the generally accepted principles of agrotechnology of sugar maize. The harvest of cobs took place at the phase of milk maturity of caryopses, which was in the other half of September. The total yield and the commercial yield of cobs were determined during the harvest according to the binding norm (PN-R-75377:1996). Besides, the studies determined the following:

• the mean height of maize plants (mean figure from 30 measurements on each plot),

• the mean number of cobs on a plant (mean figure from 30 measurements),

• the length and diameter of commercial cobs (mean figure from 30 measurements),

• the mass of commercial cobs (mean figure from 30 measurements),

• the mass of grains in 1 commercial cob (mean figure from 15 measurements).

The results were statistically analyzed, using the analysis of variance. The significance of differences of the mean figures was estimated using Tukey’s test at the level of significance of p = 0.05.

RESULTS AND DISCUSSION

The success of the cultivation of plants intended as green fertilizer and the field cultivation of vegetables depends on atmospheric conditions during their growth.

Meteorological conditions in the years of studies were differentiated (table 1). In the period of forecrop plants’ growth (April-May) in the years 2002 and 2003, the studies found out a deficit of atmospheric rainfalls as compared to the means of many years for 1951-1990. In 2002 the shortage of rainfalls was 19.5 mm, while in 2003 it was 32.9 mm. Favourable moisture conditions for the growth of forecrops were observed in 2004. In April and May, the studies observed higher rainfalls, respectively, by 6.5 mm and 42.7 mm as compared to the means of many years for those months.

The mean air temperatures during the vegetation of plants intended for ploughing in considerably differed in particular years of the experiment. The years 2002 and 2003 were characterized by cooler April and warmer May, while the year 2004 had warmer April and cooler May as compared to the means of many years for those months.

The best moisture conditions for the growth of sugar maize were observed in 2002, while by far the worst in a very dry year of 2003, when, during the vegetation of maize (June-September), the sums of rainfalls noted in all months were remarkably different from the means of many years. In August, only 4.7 rainfalls were observed. The whole period of sugar maize vegetation in 2003 was closed with a deficit of rainfalls, which was 166.2 mm.

In the climatic conditions of Poland big requirements of sugars maize in relation to the temperature and the dependence of the yield and the course of the weather during the vegetation are stressed [23]. Gradual warming of the climate has been observed for a number of years. In the years 2002-2003 temperatures higher than the means of many years were noted in the months when sugar maize stayed in the field. The year 2004 was slightly colder, with June and July temperatures lower than the means of many years for those months.

The amount of the ploughed in biomass of green fertilizers and manure as well as nitrogen introduced into the soil with them is presented in table 2. 6.40 t·ha^-1 of dry mass and 115.57 kg·ha^-1 of nitrogen were introduced into the soil with the dose of 25 t·ha^-1 of manure. Among the green fertilizers, the greatest amount of fresh mass was formed by the mixture of vetch and oat (23.58 t·ha^-1, on average) and oat in pure sowing (22.89 t·ha^-1). A high yield of fresh mass was also characteristic of the mixture of vetch with oat and field pea (21.90 t·ha^-1) and the mixture of oat with field pea (20.64 t·ha^-1). The other green fertilizers made by 30-45% less fresh mass totally as compared to the mixture of vetch with oat. The greatest quantity of crop residues was left by the mixtures of vetch with field pea (4.99 t·ha^-1) and oat with field pea (4.44 t·ha^-1), while the smallest – by field pea in pure sowing (1.47 t·ha^-1).

The highest yield of dry mass was produced by green fertilizers from oat (4.79 t·ha^-1) and the mixture of vetch with oat (4.14 t·ha^-1). The greatest amount of dry mass with crop residues was ploughed in with the roots and oat stubble (0.98 t·ha^-1) and the mixture of vetch with oat and field pea (0.97 t·ha^-1).

The greatest amount of nitrogen with the whole plants was ploughed in with the mixtures of vetch with oat (111.06 kg·ha^-1) and vetch with oat and field pea (100.11 kg·ha^-1). Considering the quantity of nitrogen contained in crop residues of green fertilizers it was found out that the greatest amount of nitrogen was introduced with the residues of the mixture of vetch with oat and field pea.

The highest yields of sugar maize were obtained in 2002 (table 3). The total yield was 18.36 t·ha^-1, while the commercial yield – 15.07 t·ha^-1. The total yield gathered in that year was significantly higher than the total yields collected in the years 2003 and 2004, while the commercial yield was significantly higher than the one obtained in 2003. Maize yielded the worst in 2003. The total yield was smaller by 20% as compared to 2002 and by 9% in comparison to 2004. On the other hand, the obtained commercial yield in 2003 was smaller in comparison to 2002 and 2004, by 18.5% and 14.5%, respectively. Worse yielding of maize in 2003 was caused by very bad moisture conditions. Michaojć et al [15] and Waligóra and Kruczek [22] state that the critical period in respect of the demand of maize for water are the seed germination and the flowering of plants. Weather conditions also affected the rate of decay of the ploughed in organic fertilizers, which, in turn, had an effect on the access of maize to the nutritious elements released from them. According to Brzeski et al. [3] and Szymankiewicz [19], the yield-forming effect of green fertilizers is related to weather conditions in the period of their decay as well as during the vegetation of the successive plant.

The analysis of the results found out a positive effect of the applied organic fertilizers on the yielding of sugar maize (table 3). The highest total yield was obtained after manure (19.52 t·ha^-1). The yield-forming effect similar to that of manure was also characteristic of green fertilizers from vetch (18.47 t·ha^-1), field pea (17.95 t·ha^-1) and a mixture of both these plants (17.92 t·ha^-1). In earlier studies conducted by the team on cabbage the best yield-forming effect among the ploughed in forecrop green fertilizers was characteristic of the mixtures of vetch with oat and field peas as well as of vetch with field pea [12]. The positive effect of papilionaceous plants, which are a valuable source of nitrogen, on the yielding of plants is also pointed out in the studies by Skrzyczyński et al. [16], Hruszko [11], Wadas [20, 21] and Franczuk et al. [9]. In an experiment with cover plants in the form of catch crops of white mustard and oat in the cultivation of maize, Konopiński and Kęsik [13] found out a higher total yield of cobs after white mustard as compared to the stand after oat.

The effect of particular organic fertilizers on the total yield of maize depended on the year of studies. In 2002 the best effect was achieved by ploughing in field pea and the mixture of vetch with field pea, in 2003 – ploughing in the mixture of vetch with field pea and vetch in pure sowing, while in 2003 – ploughing in manure.

The highest commercial yield was observed in 2002 (15.07 t·ha^-1) and slightly smaller in 2004 (14.55 t·ha^-1) (table 3). The yields in the years 2002 and 2004 were significantly higher than those obtained in 2003. All organic fertilizers used in the experiment influenced the commercial yield of maize as compared with the cultivation without organic fertilization. The highest commercial yield was obtained after manure (16.49 t·ha^-1) and after green fertilizer from field pea (16.06 t·ha^-1). The smallest increase of the commercial yield of maize as compared with the control was observed after ploughing in green fertilizer from oat (9.2%) and green fertilizer from the mixture of vetch with oat (9.7 t·ha^-1). The statistical analysis of the obtained data found out the influence of the form of fertilization with green fertilizers and the kind of organic fertilization on the size of the commercial yield of sugar maize. After ploughing in the whole biomass of green fertilizers, the highest commercial yield of maize was obtained after field pea (16.10 t·ha^-1) and the mixture of vetch with field pea (15.81 t·ha^-1). It was significantly smaller after oat, the mixtures of oat with field pea, vetch with oat and vetch with oat and field pea as well as the control without organic fertilization. The studies found out no significant differences in the commercial yield of maize as a result of ploughing in the crop residues of various green fertilizers. On the other hand, the ploughed in crop residues of green fertilizers (except the residues of the mixture of vetch with oat and field pea) had a significant effect on the increase of the commercial yield of maize as compared with the control, which did not receive organic fertilization.

The worse yielding of maize after oat and the mixtures with it can be accounted for by introducing higher quantities of biomass into the soil by those green fertilizers. As compared with other plants, they needed more nutritious elements and water to produce more green mass. Oat and its mixtures exhausted the soil of these resources more than the other plants cultivated for ploughing in. According to Borna [1, 2], the decrease of the yields of vegetables cultivated directly after the ploughed in green fertilizers, especially in the form of forecrops and winter catch crops, is directly proportional to the amount of the fresh and dry mass produced by plants intended for ploughing in.

Sugar maize differed in particular year of the experiment with the height of the plants and the number of cobs on a plant (table 4). Differentiated organic fertilization also had an effect on those features. The highest plants grew in 2002, slightly shorter – in 2004, while decisively the shortest grew in the dry year of 2003. Fertilization with manure as well as a mixture of vetch with field pea and field pea had the most positive effect on the growth of maize plants. Konopiński and Kęsik [13] found out the effect of the course of the weather on the height of sugar maize plants. They also observed that the application of white mustard as a cover plant clearly stimulated the growth of plants, as compared to oat.

Maize ‘Landmark F₁’ formed 1.5 cobs on one plant, on average. In 2002 mean 1.7 cob fell for one plant, while in the years 2003 and 2004 – 1.3 and 1.4 cob, respectively. The difference between 2002 and the years 2003 and 2004 was statistically significant. As stated by Wierzbicka [24], the number of cobs per plant as a cultivar feature can be modified by the environment. Cultivars with a bigger number of cobs are characterized by greater yielding stability [5]. The studies found out that maize cultivated after ploughing in the mixture of vetch with field pea produced significantly more cobs on a plant (1.6 cob, on average) than maize grown after ploughing in oat (1.4). In the weather conditions of 2002 maize cultivated after green fertilizers from field pea and a mixture of vetch with field pea produced significantly more cobs on 1 plants than maize grown after vetch, a mixture of vetch with oat and a mixture of vetch with oat and field pea. In 2003 the studies found out a significantly greater mean number of cobs on maize grown after a mixture of vetch with field pea and on the control without organic fertilization as compared with maize grown after ploughed in oat.

Table 5 presents the effect of the examined factors on the length and diameter of ‘Landmark F1’ sugar maize cobs. The longest cobs were produced by maize in the years 2003 (22.5 cm) and 2002 (21.2 cm), while the shortest in 2004 (20.5 cm). The cobs collected from maize cultivated on ploughed in crop residues were significantly longer (21.9 cm) than those collected from maize grown after ploughing in the whole green fertilizers (21.5 cm). No significant effect of the kind of organic fertilization on the length of sugar maize cobs was found.

The diameter of cobs collected in 2002 and 2004 (4.5 cm) was significantly bigger than the diameter of cobs in 2003 (4.1 cm). By far the greatest diameter of cobs was found for maize cultivated after ploughed in field pea (4.5 cm), while the smallest – after ploughed in vetch with oat (4.2). The form of ploughing in the green fertilizer did not have a significant effect on the diameter of maize cobs.

The studies found out a different mean mass of the commercial cob of sugar maize in particular years of the studies (table 6). The heaviest cobs were produced by maize in 2002, while significantly lighter – in 2004. The joint effect of the form of ploughing in the green fertilizer and the kind of the ploughed in fertilizer had an influence on the mass of commercial cobs. Maize grown after ploughing in the whole green fertilizers produced the heaviest cobs after vetch (326.4 g). Those cobs had a significantly higher mass than the cobs collected from maize cultivated after ploughing in a mixture of vetch with oat (232.2 g) and on the control without organic fertilization (252.4 g). Maize cultivated after ploughing in the crop residues of the mixture of vetch with oat produced significantly heavier cobs (335.4 g) than maize grown on the control without organic fertilization (255.6 g).

The experiment also established the effect of the studied factors on the mean mass of grains from 1 commercial cob. It was found out that the biggest weight of grain was characteristic of maize cobs in 2002 (150.2 g), while the smallest in 2003 (94.9 g). The differences between the sizes of this feature in particular years of studies were statistically significant. The greatest weight of grains was observed for the cobs of maize cultivated after ploughing in green fertilizer of field pea (133.7 g), while significantly the smallest for the mixture of vetch with oat and field pea (109.8 g), oat (115.7 g), manure (116.0 g) and on the control without organic fertilization (121.1 g). The best influence on the grain mass in a cob was exerted by sugar maize cultivation after ploughing in field pea in the weather conditions of 2002.

Literature lacks any reports on the effect of organic fertilization, especially in the form of green fertilizers, on the mean number of cobs on a plant of sugar maize and on the mass, length and diameter of cobs. The authors’ own studies found out that the greatest length, diameter and mass were characteristic of the cobs of maize grown after ploughed in manure and green fertilizers of papilionaceous plants. Manure provided the soil with the greatest amount of nitrogen, while papilionaceous plants ploughed in the early developmental phases probably underwent mineralization very quickly. Nitrogen released from them was immediately available for plants. Waligóra and Kruczek [22] found out in their studies that the increased dose of nitrogen supplied to the soil with mineral fertilizers is accompanied by the increased diameters of sugar maize cobs.

CONCLUSIONS

1. The greatest amount of fresh and dry mass was ploughed in with oat and its mixture with vetch. The greatest quantity of nitrogen was introduced into the soil with manure and its mixtures of vetch with oat and vetch with oat and field pea.

2. Weather conditions in particular years of studies significantly modified the yields of sugar maize, the height of plants, the number of cobs produced on 1 plant, the length, diameter and mass of the produced cobs.

3. The best yield-forming effect was characteristic of field pea, a mixture of vetch with field pea and manure in the dose of 25 t·ha^-1. The best total and commercial yields of sugar maize were achieved after those organic fertilizers.

4. The highest plants of maize grew after manure, a mixture of vetch with field pea and after field pea. The most cobs on 1 plant were found in the cultivation of maize after field pea.

5. The cobs collected from the maize grown after ploughed in crop residue were significantly longer than those that were collected from the maize cultivated after ploughed in whole green fertilizers. The longest were observed in the cultivation of maize after ploughed in field pea.

6. The greatest diameter of cobs was characteristic of maize grown after ploughed in green fertilizer of field pea.

7. The greatest mass was found for the cobs collected from maize grown after vetch. The highest mean mass of grains themselves was observed for the cobs from maize cultivated on the plots with ploughed in green fertilizer of field pea.

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