1 – INTRODUCTION
Brazil has gone for many economic changes in the 90’s, which somehow contributed to the opening of international trade, increased competitiveness, search for new technological alternative and quality products improving in view of the international consumer exigency.
By the end of the 60´s livestock was used by large landowners to characterize the land tenure. Historically, the predominant production system was extraction on native pastures, without worry with investment and technology adoption. However, this profile has changed in view of the high production costs and the rural entrepreneurs have sought alternatives to survive.
One of the biggest problems facing in the national livestock, because it is basically pasture, is the pasture degradation. In a degraded pasture the productivity is around 2 arrobas / ha / year, while in a well-managed pasture and in good condition can achieve an average of 16 arrobas / ha / year. Thus, one way to decrease the recovery cost with recuperation of pastures is through a planting grass with a grain crop.
2 – BRAZILIAN PASTURE SITUATION
The pasture area, with species grown in Brazil is around 115 million hectares (ha), while the area with native pasture is 144 million. These areas are home to around 195 million head of cattle which gives a stocking rate of 0.75 animals per hectare and a production about eight million tons of carcass.
However, soils that are under these pastures are mostly poor, with a horizon with low activity clays, which consists of a kaolinite mixture, iron oxide and quartz and with a low mineral content. Consequently, the existing native forages on these soils presents low productivity and forage established through a soil remediation for the formation of these pastures have shown, in a short period of time, a sharp decline in productivity. This short period of cultivate pasture utilization is related to an insufficient nutrients supply of soil to pasture species introduced, what leads to its degradation.
It is understood by degradation of pasture, “the evolutionary process of vigor loss, productivity, capacity of natural recuparation of pastures to sustain production levels and quality required by the animals, as well as to overcome the harmful effects of pests, diseases and weeds, culminating to the advanced degradation of natural resources, because of inadequately managed “(Macedo, 1993).
2.1 – CULTURES SUCCESSION AS A MEANS OF RECOVERY DEGRADED PASTURES
Currently, mixed systems of crop and livestock exploitation have drawn attention for the dvantages they present in relation to isolated systems of agriculture or ranching. These are called Integrated Crop-Livestock Systems, or simply Crop-Livestock Integration (ILP). The crop-livestock integration can be defined as diversification, rotation, cropping and / or sequence of activities in agriculture and livestock within the farm in harmony form, constituting the same system, so that there are benefits to both.
Allows, as one of the main advantages that the soil be economically exploited throughout the year or at least, most of it, favoring the increase of grain supply, meat and milk at a lower cost due to the synergy that is created between the crop and pasture (Alvarenga, 2004).
2.2 – OBJECTIVES OF CROP – LIVESTOCK INTEGRATION (ILP)
The main objectives of ILP can be enumerated as follows:
2.2.1 – Recuperation or renovation of degraded pastures.
This is the main goal of integration. In this system, the fields are used so that grain production will pay, at least in part, the costs of recuperation or retirement pastures. In the area of degraded pasture, grain is cultivated by one, two or more years and then turns to the pasture, which will take advantage of the residual nutrients in the production forage crops. To avoid another degradation cycle, it is necessary to draw up a schedule of maintenance fertilization of pasture newly deployed (Alvarenga, 2004). It is important to note that for most soils of Minas Gerais, as well as in Brazil, if not made maintenance fertilization, this method gives a result in the first, two or three years. After this period, the pasture suffers new cycle of degradation due to depletion of the nutrients that entered the system via the crops fertilization. So, it is necessary to cultivate crops in the area again to replenish the nutrients (Moraes, 1993).
2.2.2 – Improve the physical and biological condition of soil with pasture in the crop area.
Pastures leave appreciable amounts of straw on the soil and roots in the soil profile. This tends to increase the organic matter, that is crucial in improving the physical structure of the soil. It is also a carbon source for the meso and soil microorganisms. Moreover, the roots decomposition creates a network of tiny channels in the soil of importance in gas exchange and a downward movement of water (Moraes, 1993, Macedo and Zimmer, 1993). This new environment created by the ILP in the soil, it is essential to impact positively both the productivity and sustainability of the agricultural system.
2.2.3 – Retrieve the soil fertility with the crop in the degraded pastures area.
The chemical correction of soil and fertilizer for growing crops recover soil fertility by increasing the supply of nutrients to the pasture and, therefore, its production potential (Alvarenga, 2004).
2.2.4 – Produce grazing, conserved forage and feed grains in the dry season.
Besides the silage and grain production, ILP allows that the produced pasture in the consortium is used during the dry season. The soil profile correction provides better root development of forage which thus deepens the profile and absorbs water to greater depths, giving the soil more persistent during the dry season (Alvarenga, 2004).
2.2.5 – Reduce the costs in agriculture activity and livestock.
As there are gain in productivity of crops and pastures, lower demand for crop protection and better use of manpower, among other factors, production costs are reduced (Alvarenga, 2004, Maraschin, 1985).
2.2.6 – Increase the stability of the producer’s income.
The diversification of crops in crop rotation and the productivity increase confer greater stability of income, because it reduces the inherent risks in cultivations of a single crop (Alvarenga, 2004).
2.3 – Renovation Models or pasture reform
The pasture reform is not a new subject, but only a few years has been addressed in a comprehensive manner, due to the need for ranchers to improve the profitability of its operations by reducing costs through improvements in production efficiency. Among the various systems of pasture renewal are considered three models: the conventional system, system Barreirão (Kluthcouski et al., 1991) and Santa Fe system (Alvarenga, 2004).
2.3.1 – Conventional System
It is a simple renovation system, low technology, consisting of a lime light, disking, and planting / fertilization of new pasture with a planned time of renewal every five years. It is an estimated capacity of one head per hectare, with an average weight gain of 0.5 kg / head / day for 240 days a year.
2.3.2 – System Barreirão
This system was perfected by Kluthcouski et. al (1991) from the tillage reversed system, adapted by Seguy et. al (1984) at the Research National Center of Rice and Beans (CNPAF) EMBRAPA.
The technique is to start preparing the soil with disk harrow in the dry season to reduce the number of established plants of Brachiaria and decrease the resistance to soil preparation operations later. Then, after the first rains and with adequate humidity, it proceeds a deep plowing with 30-35 cm with a moldboard plow. This aims to put the whole organic layer and pasture seeds remaining will no depth germinate. This preparation, which often requires no more harrowing, it is possible the planting rice, with seeds in one box, and Brachiaria in another box. The technique consists of planting rice in a position more superficial position (2-3 cm) and the fertilizer and pasture seed deeper (8 cm) (Macedo and Zimmer, 1993).
The system was developed primarily for the replacement of pastures B. by B. decumbens Brizantha cv. Marandu, which take advantage the residual fertilization effect of rice in the pasture renovation. The direct effect would be the possibility of obtaining a pasture with a better nutritional value, increase the capacity of stocking and mainly to amortize costs through the sale of production rice grain (Macedo and Zimmer, 1993).
2.3.3 System – Santa Fe
Recently Embrapa Rice and Beans developed another system of pasture renovation simiar to the Barreirão system, that is Santa Fe system, which is a culture consortium, especially maize, sorghum, rice or soybeans, with tropical forages, mainly Brachiaria, although the Panicum are also widely used, even with the consortium management requiring greater care. This system has great advantage because it does not change the activities schedule of the producer and does not require special equipment for their deployment. The system consists of the simultaneous planting of grain and forage or forage planting lagged approximately 20 to 30 days after the emergence of cereal. This system aims the production of grain or forage of cereal, the production of pasture in a dry períod and the straw for the no-tillage system, although it can be used in the conventional soil preparation.
The procedures for planting cereal are the traditionall. At the planting simultaneously, depending on the forage species, the seeds are mixed with the manure of cereal. It is important to see that this mixture is made on the day of planting and to adjust the depth of deposition of manure + seeds for greater depth, taking care not to exceed the limit so that there is seedling emergence. It is desirable to establish one or two additional forage lines between the cereal lines for better pasture establishment, which will depend on the spacing and planting equipment available. Another possibility is the forage planting lagged in 20 to 30 days after the emergence of cereal, plant cereal single and when he is already established, does the forage sowing. Again, depending on the equipment, this planting can be with machines or make another sowing broadcasting.
The consortium management is not very different from the single crop. The weed control and forage in the consortium is of great importance and should be done with specific herbicides for broadleaf and with dosing of herbicides for control weed and narrow leaves selected for cereal planted. This causes a sub-dose of herbicide stress on forage, with temporary shutdown of its growth. This allows it does not compete for nutrients and water during the critical period of competition, which runs until the 50 days.
When the forage is remake of stress, the cereal is already well developed, restricting light penetration. With this, the forages will have its growth limited. At the beginning of drying the leaves of cereal, the forage will back grow faster. So the harvest should not be delayed because the forage can grow a lot and cause disorders (bushing) at the harvest. After the harvest, you should do a quick formation grazing to stimulate tillering of the forage. Following, the removal of the animals, the area should be sealed for a sufficient period for regrowth and growth until the final phase of definitely grazing, which occurs in 60 to 90 days, depending on weather conditions. If the grain is harvested for silage, the area need to be sealed until the time of the first permanent grazing.
At the end of the dry períod, the pasture is fenced and the rains began, dried starting a new cycle of consortium in a direct system planting or conventional. In many cases, ranchers have adopted this technology only to recover or renovate pastures. A fertilization program maintenance and controlled grazing has allowed the use of new pasture for an indefinite period, with high productivity. If this schedule is not implemented, the new pasture will degrade by no more than three years, being necessary to recover it again, as already pointed out (Alvarenga, 2004).
3 – IMPACT OF AGRICULTURE/ILP IN THE PRODUCTION OF CATTLE
The crop-livestock integration presents as an advantage the increasing of carrying capacity of pastures and consequently a higher animal productivity when compared to degraded systems pastures (Table 1).
Table 1 – Ability to support and cattle performance recreated, in pastures with different strategies and renewed subject to a grazing pressure of 7% in Brasilândia – MS.