Study On Planting Adaptability Of Forage Crops In Saline-alkali Farmland

Animal husbandry in China is mainly distributed in Northern China.At present,the lack of silage has become an important limiting factor for the development of herbivorous animal husbandry.There is large area of saline-alkali cultivated field in Northern China.Planting forage crops in the saline-alkali field can effectively solve the problem of shortage of silage.In this study,millet,wheat,rapeseed,soybean,sorghum,and corn,the six common forage crops of Northern China were planted in Tianjin(coastal,Na Cl type saline-alkali land)and Xinjiang(northwest inland,Na₂SO₄-Na HCO₃ type saline-alkali land)with different salt contents and saline-alkali types to study the growth and productivity of forage crops in the saline-alkali field.This study can also screen the suitable forage crops planting in the corresponding saline-alkali land blocks and identify the improvement effects of planting feed crops on saline-alkali soil.The main results are as follows:1.There were significant differences of forage crop yield and crude protein yield in different saline-alkali degree and saline-alkali type plots.The forage yield and crude protein yield of sorghum were the highest in the Na₂SO₄-Na HCO₃ saline-alkali soil with the salt content of 4.46 g/kg,which were 7.49 t/hm² and 0.80 t/hm²,respectively.Rapeseed produced the highest forage yield among the crops,while soybean acheived the highest crude protein yield,which were 4.19 t/hm² and 0.53t/hm²,separately,in the Na Cl type saline-alkali soil with the salt content of 3.63 g/kg.The forage yield of maize was the highest in the Na₂SO4-Na HCO₃ type and the Na Cl type saline-alkali soil with the soil salt content of 1.82 g/kg,which were 17.58 t/hm²and 13.72 t/hm²,respectively.The crude protein yield of rapeseed was the highest,1.81 t/hm² and 1.61 t/hm²,separately.In order to obtain the highest crude protein yield,rapeseed was the most suitable crop to be planted in the saline-alkali soil with the concentration of 1.82 g/kg-2.00 g/kg,while sorghum and soybean were suitable to be planted in the Na₂SO₄-Na HCO₃ saline-alkali soil with the concentration of 4.46g/kg and the Na Cl saline-alkali soil with the concentration of 3.63 g/kg,respectively.2.The adaptability of forage crops to saline-alkali stress was significantly different.Saline-alkali stress could inhibit the growth and development of the crops.Increased soil salt content resulted in delayed the growth period of forage crops,decreased the biomass per plantand the number and SPAD value of leaves,as well as the malondialdehyde content in leaves and roots.The tolerance of different forage crops are not the sameto the types of saline-alkali stress.Wheat,rapeseed and sorghum are more tolerant to Na Cl type and Na₂SO₄-Na HCO₃ type saline-alkali soil,while soybean has strong resistance to Na Cl type saline-alkali soil,whereas millet is more tolerant to Na₂SO₄-Na HCO₃ type.Corn has poor resistance to both types of saline-alkali soil.3.Saline-alkali stress limits the absorption of N,P and K in soil by forage crops.In our experiment,the limitation effects of Na Cl type saline-alkali soil on nutrient absorption of plants were higher than that of Na₂SO₄-Na HCO₃ type saline-alkali soil.Forage crops were suffered the greatest nutrient stress during the reproductive growth period,which decreased the nitrogen,phosphorus and potassium contents in shoot of the plants,while increased the Na⁺content.Nitrogen was the main growth limiting factor for millet,rapeseed and soybean,phosphorus was the main growth restricting factor for wheat and maize,and potassium was the main growth limiting factor for sorghum.4.Planting silage crops improved the properties of saline-alkali soil,resulted in increased the content of total nitrogen and organic matter in the saline-alkali soil,while the changes of alkali-hydrolyzable nitrogen,available phosphorus and available potassium were not significantly.The changes of total salt and Na⁺content were significant differently,which was related to the difference in the absorption of Na⁺by planting forage crops.Rapeseed was significantly superior to other forage crops in absorbing Na⁺in the soil and reducing the soil salt content.In the saline-alkali soil mass of Na Cl type and Na₂SO₄-Na HCO₃ type,the uptake of soil Na⁺by rapeseed was19.13-102.24 kg/hm² and 22.87-39.43 kg/hm²,respectively.The soil total salt and Na⁺content was significantly reduced by planting rapeseed.The absorption of Na⁺by feed crops in Na Cl type saline-alkali soil was higher than that in Na₂SO₄-Na HCO₃ type saline-alkali soil,and the absorption of Na⁺ in soil decreased with the increase of soil salt content.