engleski

Soil tillage responses to the climate threats – Revaluation of the classic theories

This study intends fulfilling two tasks. The first task was revision the classic theories related to the ploughing practice at present climate conditions. The factors that closely depended on the ploughing are the method of stubble tillage in summer, clod formation, a cloddy surface before wintering and misinterpretation of the frost effect. The second aim was evaluating the soil condition evolved by different soil tillage methods and the ranking the methods in dry and in wet seasons. The fulfilment of the tasks based on the results that were elaborated in a long-term experiment. The six tillage treatments are fairly adopted in Hungarian fields however the impartial judgement, especially in extreme seasons, is rather incomplete. Six treatments comprised deep –  0.30 m (that is loosening, L, ploughing, P, and tine tillage, T) –, and shallow –  0.22 m, (that is tine tillage, ST and disking, D) – soil disturbance along with direct drilling (DD). That is, among the treatments ploughing was also included. Attention to the ploughing has originated from the multi-year experience obtained in the regional practice. The ploughing has dutifully applied in the Pannonian region for centuries, despite of the negative consequences that have become well known both in European and in the worldwide relation. The main disadvantages of the ploughing, according to the literature are the limited depth of the loosened layer, the humus and the water loss and the soil structure deterioration. Most of the damages are visible e.g. soil kneading, pan compacting in wet seasons or soil lumping in the dry conditions. Ploughmen do not want to recognize these harms despite they are to face the negative consequences of their practice in extreme seasons. Ploughmen have regrettably remained indifferent to the sustainability ideas up to now. Changing the attitude to the ploughing practice seems to be really urgent considering the impacts of the extreme climate phenomena on ploughed soils. The second aim was studying the effects of the tillage treatments on dry and wet soils and minimizing the possible damages. Only the treatment was used might have received the optimal degree which has resulted in slighter and easily reparable damages that occurred during the dry (2011. 2012, 2015) and wet (2010, 2014, 2016) seasons. Realising the tasks that were assigned above, some important conclusions can be drawn: - Creating the black surface (by ploughing) in summer stubbles is really outdated considering the exposure of soils to the heat and the rain stress. It was found that regeneration of the soil condition after summer harvest can only be implemented by shallow soil disturbance and adequate (45-55%) surface cover. - According to the classical approach an advantage of the ploughing created large clods is the poor weed emergence in summer. Considering this practice, the weed infestation has postponed to the time after sowing. It was found that the effective weed control should be achieved in stubbles where weeds emerged in number considering the effectual soil water conservation. -Summer ploughing was acceptable despite of the clod formation because of the clod breaking effect was hoped by the alternation of the higher and lower temperature in the day and night. The reality is far from this belief, that is the fragmentation process is adequately occurred, but in the meantime the biological activity of the soil has ceased and decomposition of the stubble residues has also stopped. -According to the classic principles, stubble residues are considered to be materials that make difficulties in soil tillage therefore removed that most often. It may stress that stubble residues are source of the humus and was found to be important to alleviate soil sensitivity to the drought and the rain stress. -Leaving the ploughed surface in cloddy state is typical. The explanation is to retain more rainwater and snow. New results state the disadvantages of the ploughing in water storing capacity in contrast with subsoiling and the deep tine tillage. While the snow events are continuously decreased, catching the snow is also doubtful hence, more effective water conservation can be implemented throughout the year. - The frost effects was believed favourable in the past, considering the fragmentation of the big lumps created in autumn. Nowadays, large, kneaded lumps are produced by modern ploughs, and fragmentation occurs only in the external parts of the big lumps, and internal parts have remained unbroken during winter period. It was found that the frost effect is often dangerous on soil structure. - Frost effects were considered to be critical when amount of the frost-dust was high (50-55%) in the samples taken from the upper 10 cm layer. -The quality of the ploughing treatment in the experiment surpassed the regional average, but comparing to another treatments it proved to be less advantages. Among the findings of the long-term experiment results that occurred in both dry and wet seasons are discussed. Results state again the advantages of the ploughless tillage. -The depth of the loosened layer was the same as the depth of the tillage at the treatments where a compact pan has formerly occurred, that is after ploughing and disking. -Larger clods (with 100 mm diameter) were usually formed in ploughed soil in both dry and wet seasons. - Larger (30 mm) soil particles unwanted in the seedbed was also found in the ploughed soil due to the clean surface following primary tillage. -Ratio of the dust reached largest proportion in ploughed soil in dry periods considering the surface exposure to the climate stress factors. Both siltation and crust formation became critical in soil that ploughed earlier. - Distribution of the chopped stubble residues in the entire cultivated layer proved to be more beneficial to the decomposition and the earthworm activity than that inverted to the bottom of the ploughed layer. -The experiment made a chance establishing the optimal ratio of the surface cover. The cover ratio affected by size of the chopped residues. Thus, the chopped straw may optimal at 60-80 mm length and the chopped maize stalk at 80-100 mm. In alleviation of the heat and rain stress, 85- 100% of cover ratio was optimal after cereal and maize harvest. However, at least 40-45% of cover ratio had beneficial impact on soil protection between the period of primary tillage and winter or spring sowing. The impact of torrential rains on crumb deterioration after sowing was moderated at higher (35-40%) surface cover. -Based on the results, aim of soil tillage can also be reworded. Instead of stressing the crop requirements the soil protection has become priority in soil tillage. Soil condition research was supported by the AGRÁRKLÍMA.2 VKSZ_12-1-2013-0034 project.

soil conservation ; climate stress mitigation ; ploughing ; ploughless tillage

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